Convert legacy string formatting to f-strings (#4685)

* the changes

* Update driver.py

.flake8

@@ -1,8 +1,8 @@
 [flake8]
 # B905 should be enabled when we drop support for 3.9
-ignore = E203, E266, E501, E704, W503, B905, B907
+ignore = E203, E266, E501, E701, E704, W503, B905, B907
 # line length is intentionally set to 80 here because black uses Bugbear
-# See https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length for more details
+# See https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#bugbear for more details
 max-line-length = 80
 max-complexity = 18
 select = B,C,E,F,W,T4,B9

.git_archival.txt

@@ -1,4 +1,3 @@
 node: $Format:%H$
 node-date: $Format:%cI$
-describe-name: $Format:%(describe:tags=true,match=*[0-9]*)$
-ref-names: $Format:%D$
+describe-name: $Format:%(describe:tags=true,match=[0-9]*)$

.gitattributes

@@ -1 +1,2 @@
 .git_archival.txt  export-subst
+*.py diff=python

.github/ISSUE_TEMPLATE/bug_report.md

@@ -12,7 +12,9 @@ current development version. To confirm this, you have three options:
 
 1. Update Black's version if a newer release exists: `pip install -U black`
 2. Use the online formatter at <https://black.vercel.app/?version=main>, which will use
-   the latest main branch.
+   the latest main branch. Note that the online formatter currently runs on
+   an older version of Python and may not support newer syntax, such as the
+   extended f-string syntax added in Python 3.12.
 3. Or run _Black_ on your machine:
    - create a new virtualenv (make sure it's the same Python version);
    - clone this repository;

.github/dependabot.yml

@@ -14,4 +14,3 @@ updates:
     schedule:
       interval: "weekly"
     labels: ["skip news", "C: dependencies", "T: documentation"]
-    reviewers: ["ichard26"]

.github/workflows/diff_shades.yml

@@ -26,7 +26,7 @@ jobs:
 
       - name: Install diff-shades and support dependencies
         run: |
-          python -m pip install 'click==8.1.3' packaging urllib3
+          python -m pip install 'click>=8.1.7' packaging urllib3
           python -m pip install https://github.com/ichard26/diff-shades/archive/stable.zip
 
       - name: Calculate run configuration & metadata
@@ -34,7 +34,8 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ github.token }}
         run: >
-          python scripts/diff_shades_gha_helper.py config ${{ github.event_name }} ${{ matrix.mode }}
+          python scripts/diff_shades_gha_helper.py config ${{ github.event_name }}
+          ${{ matrix.mode }}
 
   analysis:
     name: analysis / ${{ matrix.mode }}
@@ -44,11 +45,11 @@ jobs:
       HATCH_BUILD_HOOKS_ENABLE: "1"
       # Clang is less picky with the C code it's given than gcc (and may
       # generate faster binaries too).
-      CC: clang-14
+      CC: clang-18
     strategy:
       fail-fast: false
       matrix:
-        include: ${{ fromJson(needs.configure.outputs.matrix )}}
+        include: ${{ fromJson(needs.configure.outputs.matrix) }}
 
     steps:
       - name: Checkout this repository (full clone)
@@ -64,7 +65,7 @@ jobs:
       - name: Install diff-shades and support dependencies
         run: |
           python -m pip install https://github.com/ichard26/diff-shades/archive/stable.zip
-          python -m pip install 'click==8.1.3' packaging urllib3
+          python -m pip install 'click>=8.1.7' packaging urllib3
           # After checking out old revisions, this might not exist so we'll use a copy.
           cat scripts/diff_shades_gha_helper.py > helper.py
           git config user.name "diff-shades-gha"
@@ -72,7 +73,7 @@ jobs:
 
       - name: Attempt to use cached baseline analysis
         id: baseline-cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ${{ matrix.baseline-analysis }}
           key: ${{ matrix.baseline-cache-key }}
@@ -110,19 +111,19 @@ jobs:
           ${{ matrix.baseline-analysis }} ${{ matrix.target-analysis }}
 
       - name: Upload diff report
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.mode }}-diff.html
           path: diff.html
 
       - name: Upload baseline analysis
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.baseline-analysis }}
           path: ${{ matrix.baseline-analysis }}
 
       - name: Upload target analysis
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.target-analysis }}
           path: ${{ matrix.target-analysis }}
@@ -130,14 +131,13 @@ jobs:
       - name: Generate summary file (PR only)
         if: github.event_name == 'pull_request' && matrix.mode == 'preview-changes'
         run: >
-          python helper.py comment-body
-          ${{ matrix.baseline-analysis }} ${{ matrix.target-analysis }}
-          ${{ matrix.baseline-sha }} ${{ matrix.target-sha }}
-          ${{ github.event.pull_request.number }}
+          python helper.py comment-body ${{ matrix.baseline-analysis }}
+          ${{ matrix.target-analysis }} ${{ matrix.baseline-sha }}
+          ${{ matrix.target-sha }} ${{ github.event.pull_request.number }}
 
       - name: Upload summary file (PR only)
         if: github.event_name == 'pull_request' && matrix.mode == 'preview-changes'
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: .pr-comment.json
           path: .pr-comment.json

.github/workflows/diff_shades_comment.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Try to find pre-existing PR comment
         if: steps.metadata.outputs.needs-comment == 'true'
         id: find-comment
-        uses: peter-evans/find-comment@a54c31d7fa095754bfef525c0c8e5e5674c4b4b1
+        uses: peter-evans/find-comment@3eae4d37986fb5a8592848f6a574fdf654e61f9e
         with:
           issue-number: ${{ steps.metadata.outputs.pr-number }}
           comment-author: "github-actions[bot]"
@@ -41,7 +41,7 @@ jobs:
 
       - name: Create or update PR comment
         if: steps.metadata.outputs.needs-comment == 'true'
-        uses: peter-evans/create-or-update-comment@23ff15729ef2fc348714a3bb66d2f655ca9066f2
+        uses: peter-evans/create-or-update-comment@71345be0265236311c031f5c7866368bd1eff043
         with:
           comment-id: ${{ steps.find-comment.outputs.comment-id }}
           issue-number: ${{ steps.metadata.outputs.pr-number }}

.github/workflows/doc.yml

@@ -26,13 +26,15 @@ jobs:
       - name: Set up latest Python
         uses: actions/setup-python@v5
         with:
-          python-version: "*"
+          python-version: "3.13"
+          allow-prereleases: true
 
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip setuptools wheel
-          python -m pip install -e ".[d]"
-          python -m pip install -r "docs/requirements.txt"
+          python -m pip install uv
+          python -m uv venv
+          python -m uv pip install -e ".[d]"
+          python -m uv pip install -r "docs/requirements.txt"
 
       - name: Build documentation
         run: sphinx-build -a -b html -W --keep-going docs/ docs/_build

.github/workflows/docker.yml

@@ -36,7 +36,7 @@ jobs:
           latest_non_release)" >> $GITHUB_ENV
 
       - name: Build and push
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           platforms: linux/amd64,linux/arm64
@@ -47,7 +47,7 @@ jobs:
         if:
           ${{ github.event_name == 'release' && github.event.action == 'published' &&
           !github.event.release.prerelease }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           platforms: linux/amd64,linux/arm64
@@ -58,7 +58,7 @@ jobs:
         if:
           ${{ github.event_name == 'release' && github.event.action == 'published' &&
           github.event.release.prerelease }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           platforms: linux/amd64,linux/arm64

.github/workflows/fuzz.yml

@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12.4", "3.13"]
 
     steps:
       - uses: actions/checkout@v4
@@ -31,6 +31,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
+          allow-prereleases: true
 
       - name: Install dependencies
         run: |

.github/workflows/lint.yml

@@ -26,7 +26,8 @@ jobs:
       - name: Set up latest Python
         uses: actions/setup-python@v5
         with:
-          python-version: "*"
+          python-version: "3.13"
+          allow-prereleases: true
 
       - name: Install dependencies
         run: |
@@ -35,8 +36,13 @@ jobs:
           python -m pip install tox
 
       - name: Run pre-commit hooks
-        uses: pre-commit/action@v3.0.0
+        uses: pre-commit/action@v3.0.1
 
       - name: Format ourselves
         run: |
           tox -e run_self
+
+      - name: Regenerate schema
+        run: |
+          tox -e generate_schema
+          git diff --exit-code

.github/workflows/pypi_upload.yml

@@ -23,7 +23,8 @@ jobs:
       - name: Set up latest Python
         uses: actions/setup-python@v5
         with:
-          python-version: "*"
+          python-version: "3.13"
+          allow-prereleases: true
 
       - name: Install latest pip, build, twine
         run: |
@@ -46,10 +47,11 @@ jobs:
       include: ${{ steps.set-matrix.outputs.include }}
     steps:
       - uses: actions/checkout@v4
+      # Keep cibuildwheel version in sync with below
       - name: Install cibuildwheel and pypyp
         run: |
-          pipx install cibuildwheel==2.15.0
-          pipx install pypyp==1
+          pipx install cibuildwheel==2.22.0
+          pipx install pypyp==1.3.0
       - name: generate matrix
         if: github.event_name != 'pull_request'
         run: |
@@ -73,7 +75,7 @@ jobs:
             | pyp 'json.dumps({"only": x, "os": "ubuntu-latest"})'
           } | pyp 'json.dumps(list(map(json.loads, lines)))' > /tmp/matrix
         env:
-          CIBW_BUILD: "cp38-* cp312-*"
+          CIBW_BUILD: "cp39-* cp313-*"
           CIBW_ARCHS_LINUX: x86_64
       - id: set-matrix
         run: echo "include=$(cat /tmp/matrix)" | tee -a $GITHUB_OUTPUT
@@ -89,14 +91,15 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - uses: pypa/cibuildwheel@v2.16.2
+      # Keep cibuildwheel version in sync with above
+      - uses: pypa/cibuildwheel@v2.23.3
         with:
           only: ${{ matrix.only }}
 
       - name: Upload wheels as workflow artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
-          name: ${{ matrix.name }}-mypyc-wheels
+          name: ${{ matrix.only }}-mypyc-wheels
           path: ./wheelhouse/*.whl
 
       - if: github.event_name == 'release'

.github/workflows/release_tests.yml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: ["3.12"]
+        python-version: ["3.13"]
         os: [macOS-latest, ubuntu-latest, windows-latest]
 
     steps:

.github/workflows/test.yml

@@ -31,7 +31,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "pypy-3.9"]
+        python-version: ["3.9", "3.10", "3.11", "3.12.4", "3.13", "pypy-3.9"]
         os: [ubuntu-latest, macOS-latest, windows-latest]
 
     steps:
@@ -41,6 +41,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
+          allow-prereleases: true
 
       - name: Install tox
         run: |
@@ -62,7 +63,7 @@ jobs:
         if:
           github.repository == 'psf/black' && matrix.os == 'ubuntu-latest' &&
           !startsWith(matrix.python-version, 'pypy')
-        uses: AndreMiras/coveralls-python-action@8799c9f4443ac4201d2e2f2c725d577174683b99
+        uses: AndreMiras/coveralls-python-action@ac868b9540fad490f7ca82b8ca00480fd751ed19
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           parallel: true
@@ -77,7 +78,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Send finished signal to Coveralls
-        uses: AndreMiras/coveralls-python-action@8799c9f4443ac4201d2e2f2c725d577174683b99
+        uses: AndreMiras/coveralls-python-action@ac868b9540fad490f7ca82b8ca00480fd751ed19
         with:
           parallel-finished: true
           debug: true
@@ -98,7 +99,7 @@ jobs:
       - name: Set up latest Python
         uses: actions/setup-python@v5
         with:
-          python-version: "*"
+          python-version: "3.12.4"
 
       - name: Install black with uvloop
         run: |
@@ -106,4 +107,4 @@ jobs:
           python -m pip install -e ".[uvloop]"
 
       - name: Format ourselves
-        run: python -m black --check .
+        run: python -m black --check src/ tests/

.github/workflows/upload_binary.yml

@@ -13,13 +13,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [windows-2019, ubuntu-20.04, macos-latest]
+        os: [windows-2019, ubuntu-22.04, macos-latest]
         include:
           - os: windows-2019
             pathsep: ";"
             asset_name: black_windows.exe
             executable_mime: "application/vnd.microsoft.portable-executable"
-          - os: ubuntu-20.04
+          - os: ubuntu-22.04
             pathsep: ":"
             asset_name: black_linux
             executable_mime: "application/x-executable"
@@ -34,7 +34,7 @@ jobs:
       - name: Set up latest Python
         uses: actions/setup-python@v5
         with:
-          python-version: "*"
+          python-version: "3.12.4"
 
       - name: Install Black and PyInstaller
         run: |

.gitignore

@@ -25,3 +25,4 @@ src/_black_version.py
 .hypothesis/
 venv/
 .ipynb_checkpoints/
+node_modules/

.pre-commit-config.yaml

@@ -24,47 +24,57 @@ repos:
         additional_dependencies: *version_check_dependencies
 
   - repo: https://github.com/pycqa/isort
-    rev: 5.12.0
+    rev: 6.0.1
     hooks:
       - id: isort
 
   - repo: https://github.com/pycqa/flake8
-    rev: 6.1.0
+    rev: 7.2.0
     hooks:
       - id: flake8
         additional_dependencies:
-          - flake8-bugbear
+          - flake8-bugbear==24.2.6
           - flake8-comprehensions
           - flake8-simplify
         exclude: ^src/blib2to3/
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.7.1
+    rev: v1.15.0
     hooks:
       - id: mypy
-        exclude: ^docs/conf.py
-        args: ["--config-file", "pyproject.toml"]
-        additional_dependencies:
+        exclude: ^(docs/conf.py|scripts/generate_schema.py)$
+        args: []
+        additional_dependencies: &mypy_deps
           - types-PyYAML
+          - types-atheris
           - tomli >= 0.2.6, < 2.0.0
-          - click >= 8.1.0, != 8.1.4, != 8.1.5
+          - click >= 8.2.0
+          # Click is intentionally out-of-sync with pyproject.toml
+          # v8.2 has breaking changes. We work around them at runtime, but we need the newer stubs.
           - packaging >= 22.0
           - platformdirs >= 2.1.0
+          - pytokens >= 0.1.10
           - pytest
           - hypothesis
           - aiohttp >= 3.7.4
           - types-commonmark
           - urllib3
           - hypothesmith
+      - id: mypy
+        name: mypy (Python 3.10)
+        files: scripts/generate_schema.py
+        args: ["--python-version=3.10"]
+        additional_dependencies: *mypy_deps
 
-  - repo: https://github.com/pre-commit/mirrors-prettier
-    rev: v3.0.3
+  - repo: https://github.com/rbubley/mirrors-prettier
+    rev: v3.5.3
     hooks:
       - id: prettier
+        types_or: [markdown, yaml, json]
         exclude: \.github/workflows/diff_shades\.yml
 
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.4.0
+    rev: v5.0.0
     hooks:
       - id: end-of-file-fixer
       - id: trailing-whitespace

.pre-commit-hooks.yaml

@@ -4,7 +4,6 @@
   name: black
   description: "Black: The uncompromising Python code formatter"
   entry: black
-  stages: [pre-commit, pre-merge-commit, pre-push, manual]
   language: python
   minimum_pre_commit_version: 2.9.2
   require_serial: true
@@ -14,7 +13,6 @@
   description:
     "Black: The uncompromising Python code formatter (with Jupyter Notebook support)"
   entry: black
-  stages: [pre-commit, pre-merge-commit, pre-push, manual]
   language: python
   minimum_pre_commit_version: 2.9.2
   require_serial: true

.readthedocs.yaml

@@ -16,3 +16,6 @@ python:
       path: .
       extra_requirements:
         - d
+
+sphinx:
+  configuration: docs/conf.py

AUTHORS.md

@@ -181,6 +181,7 @@ Multiple contributions by:
 - [Tony Narlock](mailto:tony@git-pull.com)
 - [Tsuyoshi Hombashi](mailto:tsuyoshi.hombashi@gmail.com)
 - [Tushar Chandra](mailto:tusharchandra2018@u.northwestern.edu)
+- [Tushar Sadhwani](mailto:tushar.sadhwani000@gmail.com)
 - [Tzu-ping Chung](mailto:uranusjr@gmail.com)
 - [Utsav Shah](mailto:ukshah2@illinois.edu)
 - utsav-dbx

CHANGES.md

@@ -1,5 +1,412 @@
 # Change Log
 
+## Unreleased
+
+### Highlights
+
+<!-- Include any especially major or disruptive changes here -->
+
+### Stable style
+
+<!-- Changes that affect Black's stable style -->
+
+- Fix crash while formatting a long `del` statement containing tuples (#4628)
+- Fix crash while formatting expressions using the walrus operator in complex `with`
+  statements (#4630)
+- Handle `# fmt: skip` followed by a comment at the end of file (#4635)
+- Fix crash when a tuple appears in the `as` clause of a `with` statement (#4634)
+- Fix crash when tuple is used as a context manager inside a `with` statement (#4646)
+- Fix crash on a `\\r\n` (#4673)
+- Fix crash on `await ...` (where `...` is a literal `Ellipsis`) (#4676)
+- Remove support for pre-python 3.7 `await/async` as soft keywords/variable names
+  (#4676)
+
+### Preview style
+
+<!-- Changes that affect Black's preview style -->
+
+- Fix a bug where one-liner functions/conditionals marked with `# fmt: skip` would still
+  be formatted (#4552)
+
+### Configuration
+
+<!-- Changes to how Black can be configured -->
+
+### Packaging
+
+<!-- Changes to how Black is packaged, such as dependency requirements -->
+
+### Parser
+
+<!-- Changes to the parser or to version autodetection -->
+
+- Rewrite tokenizer to improve performance and compliance (#4536)
+- Fix bug where certain unusual expressions (e.g., lambdas) were not accepted in type
+  parameter bounds and defaults. (#4602)
+
+### Performance
+
+<!-- Changes that improve Black's performance. -->
+
+### Output
+
+<!-- Changes to Black's terminal output and error messages -->
+
+### _Blackd_
+
+<!-- Changes to blackd -->
+
+### Integrations
+
+<!-- For example, Docker, GitHub Actions, pre-commit, editors -->
+
+- Fix the version check in the vim file to reject Python 3.8 (#4567)
+- Enhance GitHub Action `psf/black` to read Black version from an additional section in
+  pyproject.toml: `[project.dependency-groups]` (#4606)
+
+### Documentation
+
+<!-- Major changes to documentation and policies. Small docs changes
+     don't need a changelog entry. -->
+
+## 25.1.0
+
+### Highlights
+
+This release introduces the new 2025 stable style (#4558), stabilizing the following
+changes:
+
+- Normalize casing of Unicode escape characters in strings to lowercase (#2916)
+- Fix inconsistencies in whether certain strings are detected as docstrings (#4095)
+- Consistently add trailing commas to typed function parameters (#4164)
+- Remove redundant parentheses in if guards for case blocks (#4214)
+- Add parentheses to if clauses in case blocks when the line is too long (#4269)
+- Whitespace before `# fmt: skip` comments is no longer normalized (#4146)
+- Fix line length computation for certain expressions that involve the power operator
+  (#4154)
+- Check if there is a newline before the terminating quotes of a docstring (#4185)
+- Fix type annotation spacing between `*` and more complex type variable tuple (#4440)
+
+The following changes were not in any previous release:
+
+- Remove parentheses around sole list items (#4312)
+- Generic function definitions are now formatted more elegantly: parameters are split
+  over multiple lines first instead of type parameter definitions (#4553)
+
+### Stable style
+
+- Fix formatting cells in IPython notebooks with magic methods and starting or trailing
+  empty lines (#4484)
+- Fix crash when formatting `with` statements containing tuple generators/unpacking
+  (#4538)
+
+### Preview style
+
+- Fix/remove string merging changing f-string quotes on f-strings with internal quotes
+  (#4498)
+- Collapse multiple empty lines after an import into one (#4489)
+- Prevent `string_processing` and `wrap_long_dict_values_in_parens` from removing
+  parentheses around long dictionary values (#4377)
+- Move `wrap_long_dict_values_in_parens` from the unstable to preview style (#4561)
+
+### Packaging
+
+- Store license identifier inside the `License-Expression` metadata field, see
+  [PEP 639](https://peps.python.org/pep-0639/). (#4479)
+
+### Performance
+
+- Speed up the `is_fstring_start` function in Black's tokenizer (#4541)
+
+### Integrations
+
+- If using stdin with `--stdin-filename` set to a force excluded path, stdin won't be
+  formatted. (#4539)
+
+## 24.10.0
+
+### Highlights
+
+- Black is now officially tested with Python 3.13 and provides Python 3.13
+  mypyc-compiled wheels. (#4436) (#4449)
+- Black will issue an error when used with Python 3.12.5, due to an upstream memory
+  safety issue in Python 3.12.5 that can cause Black's AST safety checks to fail. Please
+  use Python 3.12.6 or Python 3.12.4 instead. (#4447)
+- Black no longer supports running with Python 3.8 (#4452)
+
+### Stable style
+
+- Fix crashes involving comments in parenthesised return types or `X | Y` style unions.
+  (#4453)
+- Fix skipping Jupyter cells with unknown `%%` magic (#4462)
+
+### Preview style
+
+- Fix type annotation spacing between * and more complex type variable tuple (i.e. `def
+  fn(*args: *tuple[*Ts, T]) -> None: pass`) (#4440)
+
+### Caching
+
+- Fix bug where the cache was shared between runs with and without `--unstable` (#4466)
+
+### Packaging
+
+- Upgrade version of mypyc used to 1.12 beta (#4450) (#4449)
+- `blackd` now requires a newer version of aiohttp. (#4451)
+
+### Output
+
+- Added Python target version information on parse error (#4378)
+- Add information about Black version to internal error messages (#4457)
+
+## 24.8.0
+
+### Stable style
+
+- Fix crash when `# fmt: off` is used before a closing parenthesis or bracket. (#4363)
+
+### Packaging
+
+- Packaging metadata updated: docs are explictly linked, the issue tracker is now also
+  linked. This improves the PyPI listing for Black. (#4345)
+
+### Parser
+
+- Fix regression where Black failed to parse a multiline f-string containing another
+  multiline string (#4339)
+- Fix regression where Black failed to parse an escaped single quote inside an f-string
+  (#4401)
+- Fix bug with Black incorrectly parsing empty lines with a backslash (#4343)
+- Fix bugs with Black's tokenizer not handling `\{` inside f-strings very well (#4422)
+- Fix incorrect line numbers in the tokenizer for certain tokens within f-strings
+  (#4423)
+
+### Performance
+
+- Improve performance when a large directory is listed in `.gitignore` (#4415)
+
+### _Blackd_
+
+- Fix blackd (and all extras installs) for docker container (#4357)
+
+## 24.4.2
+
+This is a bugfix release to fix two regressions in the new f-string parser introduced in
+24.4.1.
+
+### Parser
+
+- Fix regression where certain complex f-strings failed to parse (#4332)
+
+### Performance
+
+- Fix bad performance on certain complex string literals (#4331)
+
+## 24.4.1
+
+### Highlights
+
+- Add support for the new Python 3.12 f-string syntax introduced by PEP 701 (#3822)
+
+### Stable style
+
+- Fix crash involving indented dummy functions containing newlines (#4318)
+
+### Parser
+
+- Add support for type parameter defaults, a new syntactic feature added to Python 3.13
+  by PEP 696 (#4327)
+
+### Integrations
+
+- Github Action now works even when `git archive` is skipped (#4313)
+
+## 24.4.0
+
+### Stable style
+
+- Fix unwanted crashes caused by AST equivalency check (#4290)
+
+### Preview style
+
+- `if` guards in `case` blocks are now wrapped in parentheses when the line is too long.
+  (#4269)
+- Stop moving multiline strings to a new line unless inside brackets (#4289)
+
+### Integrations
+
+- Add a new option `use_pyproject` to the GitHub Action `psf/black`. This will read the
+  Black version from `pyproject.toml`. (#4294)
+
+## 24.3.0
+
+### Highlights
+
+This release is a milestone: it fixes Black's first CVE security vulnerability. If you
+run Black on untrusted input, or if you habitually put thousands of leading tab
+characters in your docstrings, you are strongly encouraged to upgrade immediately to fix
+[CVE-2024-21503](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-21503).
+
+This release also fixes a bug in Black's AST safety check that allowed Black to make
+incorrect changes to certain f-strings that are valid in Python 3.12 and higher.
+
+### Stable style
+
+- Don't move comments along with delimiters, which could cause crashes (#4248)
+- Strengthen AST safety check to catch more unsafe changes to strings. Previous versions
+  of Black would incorrectly format the contents of certain unusual f-strings containing
+  nested strings with the same quote type. Now, Black will crash on such strings until
+  support for the new f-string syntax is implemented. (#4270)
+- Fix a bug where line-ranges exceeding the last code line would not work as expected
+  (#4273)
+
+### Performance
+
+- Fix catastrophic performance on docstrings that contain large numbers of leading tab
+  characters. This fixes
+  [CVE-2024-21503](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-21503).
+  (#4278)
+
+### Documentation
+
+- Note what happens when `--check` is used with `--quiet` (#4236)
+
+## 24.2.0
+
+### Stable style
+
+- Fixed a bug where comments where mistakenly removed along with redundant parentheses
+  (#4218)
+
+### Preview style
+
+- Move the `hug_parens_with_braces_and_square_brackets` feature to the unstable style
+  due to an outstanding crash and proposed formatting tweaks (#4198)
+- Fixed a bug where base expressions caused inconsistent formatting of \*\* in tenary
+  expression (#4154)
+- Checking for newline before adding one on docstring that is almost at the line limit
+  (#4185)
+- Remove redundant parentheses in `case` statement `if` guards (#4214).
+
+### Configuration
+
+- Fix issue where _Black_ would ignore input files in the presence of symlinks (#4222)
+- _Black_ now ignores `pyproject.toml` that is missing a `tool.black` section when
+  discovering project root and configuration. Since _Black_ continues to use version
+  control as an indicator of project root, this is expected to primarily change behavior
+  for users in a monorepo setup (desirably). If you wish to preserve previous behavior,
+  simply add an empty `[tool.black]` to the previously discovered `pyproject.toml`
+  (#4204)
+
+### Output
+
+- Black will swallow any `SyntaxWarning`s or `DeprecationWarning`s produced by the `ast`
+  module when performing equivalence checks (#4189)
+
+### Integrations
+
+- Add a JSONSchema and provide a validate-pyproject entry-point (#4181)
+
+## 24.1.1
+
+Bugfix release to fix a bug that made Black unusable on certain file systems with strict
+limits on path length.
+
+### Preview style
+
+- Consistently add trailing comma on typed parameters (#4164)
+
+### Configuration
+
+- Shorten the length of the name of the cache file to fix crashes on file systems that
+  do not support long paths (#4176)
+
+## 24.1.0
+
+### Highlights
+
+This release introduces the new 2024 stable style (#4106), stabilizing the following
+changes:
+
+- Add parentheses around `if`-`else` expressions (#2278)
+- Dummy class and function implementations consisting only of `...` are formatted more
+  compactly (#3796)
+- If an assignment statement is too long, we now prefer splitting on the right-hand side
+  (#3368)
+- Hex codes in Unicode escape sequences are now standardized to lowercase (#2916)
+- Allow empty first lines at the beginning of most blocks (#3967, #4061)
+- Add parentheses around long type annotations (#3899)
+- Enforce newline after module docstrings (#3932, #4028)
+- Fix incorrect magic trailing comma handling in return types (#3916)
+- Remove blank lines before class docstrings (#3692)
+- Wrap multiple context managers in parentheses if combined in a single `with` statement
+  (#3489)
+- Fix bug in line length calculations for power operations (#3942)
+- Add trailing commas to collection literals even if there's a comment after the last
+  entry (#3393)
+- When using `--skip-magic-trailing-comma` or `-C`, trailing commas are stripped from
+  subscript expressions with more than 1 element (#3209)
+- Add extra blank lines in stubs in a few cases (#3564, #3862)
+- Accept raw strings as docstrings (#3947)
+- Split long lines in case blocks (#4024)
+- Stop removing spaces from walrus operators within subscripts (#3823)
+- Fix incorrect formatting of certain async statements (#3609)
+- Allow combining `# fmt: skip` with other comments (#3959)
+
+There are already a few improvements in the `--preview` style, which are slated for the
+2025 stable style. Try them out and
+[share your feedback](https://github.com/psf/black/issues). In the past, the preview
+style has included some features that we were not able to stabilize. This year, we're
+adding a separate `--unstable` style for features with known problems. Now, the
+`--preview` style only includes features that we actually expect to make it into next
+year's stable style.
+
+### Stable style
+
+Several bug fixes were made in features that are moved to the stable style in this
+release:
+
+- Fix comment handling when parenthesising conditional expressions (#4134)
+- Fix bug where spaces were not added around parenthesized walruses in subscripts,
+  unlike other binary operators (#4109)
+- Remove empty lines before docstrings in async functions (#4132)
+- Address a missing case in the change to allow empty lines at the beginning of all
+  blocks, except immediately before a docstring (#4130)
+- For stubs, fix logic to enforce empty line after nested classes with bodies (#4141)
+
+### Preview style
+
+- Add `--unstable` style, covering preview features that have known problems that would
+  block them from going into the stable style. Also add the `--enable-unstable-feature`
+  flag; for example, use
+  `--enable-unstable-feature hug_parens_with_braces_and_square_brackets` to apply this
+  preview feature throughout 2024, even if a later Black release downgrades the feature
+  to unstable (#4096)
+- Format module docstrings the same as class and function docstrings (#4095)
+- Fix crash when using a walrus in a dictionary (#4155)
+- Fix unnecessary parentheses when wrapping long dicts (#4135)
+- Stop normalizing spaces before `# fmt: skip` comments (#4146)
+
+### Configuration
+
+- Print warning when configuration in `pyproject.toml` contains an invalid key (#4165)
+- Fix symlink handling, properly ignoring symlinks that point outside of root (#4161)
+- Fix cache mtime logic that resulted in false positive cache hits (#4128)
+- Remove the long-deprecated `--experimental-string-processing` flag. This feature can
+  currently be enabled with `--preview --enable-unstable-feature string_processing`.
+  (#4096)
+
+### Integrations
+
+- Revert the change to run Black's pre-commit integration only on specific git hooks
+  (#3940) for better compatibility with older versions of pre-commit (#4137)
+
+## 23.12.1
+
+### Packaging
+
+- Fixed a bug that included dependencies from the `d` extra by default (#4108)
+
 ## 23.12.0
 
 ### Highlights

CONTRIBUTING.md

@@ -1,10 +1,13 @@
 # Contributing to _Black_
 
-Welcome! Happy to see you willing to make the project better. Have you read the entire
-[user documentation](https://black.readthedocs.io/en/latest/) yet?
+Welcome future contributor! We're happy to see you willing to make the project better.
 
-Our [contributing documentation](https://black.readthedocs.org/en/latest/contributing/)
-contains details on all you need to know about contributing to _Black_, the basics to
-the internals of _Black_.
+If you aren't familiar with _Black_, or are looking for documentation on something
+specific, the [user documentation](https://black.readthedocs.io/en/latest/) is the best
+place to look.
 
-We look forward to your contributions!
+For getting started on contributing, please read the
+[contributing documentation](https://black.readthedocs.org/en/latest/contributing/) for
+all you need to know.
+
+Thank you, and we look forward to your contributions!

Dockerfile

@@ -10,7 +10,8 @@ RUN python -m venv $VIRTUAL_ENV
 RUN python -m pip install --no-cache-dir hatch hatch-fancy-pypi-readme hatch-vcs
 RUN . /opt/venv/bin/activate && pip install --no-cache-dir --upgrade pip setuptools \
     && cd /src && hatch build -t wheel \
-    && pip install --no-cache-dir dist/*-cp*[colorama,d,uvloop]
+    && pip install --no-cache-dir dist/*-cp* \
+    && pip install black[colorama,d,uvloop]
 
 FROM python:3.12-slim
 

README.md

@@ -38,7 +38,7 @@ Try it out now using the [Black Playground](https://black.vercel.app). Watch the
 
 ### Installation
 
-_Black_ can be installed by running `pip install black`. It requires Python 3.8+ to run.
+_Black_ can be installed by running `pip install black`. It requires Python 3.9+ to run.
 If you want to format Jupyter Notebooks, install with `pip install "black[jupyter]"`.
 
 If you can't wait for the latest _hotness_ and want to install from GitHub, use:
@@ -137,8 +137,8 @@ SQLAlchemy, Poetry, PyPA applications (Warehouse, Bandersnatch, Pipenv, virtuale
 pandas, Pillow, Twisted, LocalStack, every Datadog Agent Integration, Home Assistant,
 Zulip, Kedro, OpenOA, FLORIS, ORBIT, WOMBAT, and many more.
 
-The following organizations use _Black_: Facebook, Dropbox, KeepTruckin, Lyft, Mozilla,
-Quora, Duolingo, QuantumBlack, Tesla, Archer Aviation.
+The following organizations use _Black_: Dropbox, KeepTruckin, Lyft, Mozilla, Quora,
+Duolingo, QuantumBlack, Tesla, Archer Aviation.
 
 Are we missing anyone? Let us know.
 

action.yml

@@ -27,6 +27,10 @@ inputs:
     description: 'Python Version specifier (PEP440) - e.g. "21.5b1"'
     required: false
     default: ""
+  use_pyproject:
+    description: Read Black version specifier from pyproject.toml if `true`.
+    required: false
+    default: "false"
   summary:
     description: "Whether to add the output to the workflow summary"
     required: false
@@ -70,5 +74,6 @@ runs:
         INPUT_JUPYTER: ${{ inputs.jupyter }}
         INPUT_BLACK_ARGS: ${{ inputs.black_args }}
         INPUT_VERSION: ${{ inputs.version }}
+        INPUT_USE_PYPROJECT: ${{ inputs.use_pyproject }}
         pythonioencoding: utf-8
       shell: bash

action/main.py

@@ -1,9 +1,11 @@
 import os
+import re
 import shlex
 import shutil
 import sys
 from pathlib import Path
 from subprocess import PIPE, STDOUT, run
+from typing import Union
 
 ACTION_PATH = Path(os.environ["GITHUB_ACTION_PATH"])
 ENV_PATH = ACTION_PATH / ".black-env"
@@ -13,12 +15,109 @@
 JUPYTER = os.getenv("INPUT_JUPYTER") == "true"
 BLACK_ARGS = os.getenv("INPUT_BLACK_ARGS", default="")
 VERSION = os.getenv("INPUT_VERSION", default="")
+USE_PYPROJECT = os.getenv("INPUT_USE_PYPROJECT") == "true"
+
+BLACK_VERSION_RE = re.compile(r"^black([^A-Z0-9._-]+.*)$", re.IGNORECASE)
+EXTRAS_RE = re.compile(r"\[.*\]")
+EXPORT_SUBST_FAIL_RE = re.compile(r"\$Format:.*\$")
+
+
+def determine_version_specifier() -> str:
+    """Determine the version of Black to install.
+
+    The version can be specified either via the `with.version` input or via the
+    pyproject.toml file if `with.use_pyproject` is set to `true`.
+    """
+    if USE_PYPROJECT and VERSION:
+        print(
+            "::error::'with.version' and 'with.use_pyproject' inputs are "
+            "mutually exclusive.",
+            file=sys.stderr,
+            flush=True,
+        )
+        sys.exit(1)
+    if USE_PYPROJECT:
+        return read_version_specifier_from_pyproject()
+    elif VERSION and VERSION[0] in "0123456789":
+        return f"=={VERSION}"
+    else:
+        return VERSION
+
+
+def read_version_specifier_from_pyproject() -> str:
+    if sys.version_info < (3, 11):
+        print(
+            "::error::'with.use_pyproject' input requires Python 3.11 or later.",
+            file=sys.stderr,
+            flush=True,
+        )
+        sys.exit(1)
+
+    import tomllib  # type: ignore[import-not-found,unreachable]
+
+    try:
+        with Path("pyproject.toml").open("rb") as fp:
+            pyproject = tomllib.load(fp)
+    except FileNotFoundError:
+        print(
+            "::error::'with.use_pyproject' input requires a pyproject.toml file.",
+            file=sys.stderr,
+            flush=True,
+        )
+        sys.exit(1)
+
+    version = pyproject.get("tool", {}).get("black", {}).get("required-version")
+    if version is not None:
+        return f"=={version}"
+
+    arrays = [
+        *pyproject.get("dependency-groups", {}).values(),
+        pyproject.get("project", {}).get("dependencies"),
+        *pyproject.get("project", {}).get("optional-dependencies", {}).values(),
+    ]
+    for array in arrays:
+        version = find_black_version_in_array(array)
+        if version is not None:
+            break
+
+    if version is None:
+        print(
+            "::error::'black' dependency missing from pyproject.toml.",
+            file=sys.stderr,
+            flush=True,
+        )
+        sys.exit(1)
+
+    return version
+
+
+def find_black_version_in_array(array: object) -> Union[str, None]:
+    if not isinstance(array, list):
+        return None
+    try:
+        for item in array:
+            # Rudimentary PEP 508 parsing.
+            item = item.split(";")[0]
+            item = EXTRAS_RE.sub("", item).strip()
+            if item == "black":
+                print(
+                    "::error::Version specifier missing for 'black' dependency in "
+                    "pyproject.toml.",
+                    file=sys.stderr,
+                    flush=True,
+                )
+                sys.exit(1)
+            elif m := BLACK_VERSION_RE.match(item):
+                return m.group(1).strip()
+    except TypeError:
+        pass
+
+    return None
+
 
 run([sys.executable, "-m", "venv", str(ENV_PATH)], check=True)
 
-version_specifier = VERSION
-if VERSION and VERSION[0] in "0123456789":
-    version_specifier = f"=={VERSION}"
+version_specifier = determine_version_specifier()
 if JUPYTER:
     extra_deps = "[colorama,jupyter]"
 else:
@@ -38,7 +137,11 @@
     # expected format is one of:
     # - 23.1.0
     # - 23.1.0-51-g448bba7
-    if describe_name.count("-") < 2:
+    # - $Format:%(describe:tags=true,match=*[0-9]*)$ (if export-subst fails)
+    if (
+        describe_name.count("-") < 2
+        and EXPORT_SUBST_FAIL_RE.match(describe_name) is None
+    ):
         # the action's commit matches a tag exactly, install exact version from PyPI
         req = f"black{extra_deps}=={describe_name}"
     else:

autoload/black.vim

@@ -75,8 +75,8 @@ def _initialize_black_env(upgrade=False):
       return True
 
   pyver = sys.version_info[:3]
-  if pyver < (3, 8):
-    print("Sorry, Black requires Python 3.8+ to run.")
+  if pyver < (3, 9):
+    print("Sorry, Black requires Python 3.9+ to run.")
     return False
 
   from pathlib import Path

docs/compatible_configs/flake8/.flake8

@@ -1,3 +1,3 @@
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701

docs/compatible_configs/flake8/setup.cfg

@@ -1,3 +1,3 @@
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701

docs/compatible_configs/flake8/tox.ini

@@ -1,3 +1,3 @@
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701

docs/compatible_configs/pycodestyle/.flake8

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 88
+ignore = E203,E701

docs/compatible_configs/pycodestyle/setup.cfg

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 88
+ignore = E203,E701

docs/compatible_configs/pycodestyle/tox.ini

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 88
+ignore = E203,E701

docs/conf.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 #
 # Configuration file for the Sphinx documentation builder.
 #
@@ -14,10 +13,12 @@
 #
 
 import os
+import re
 import string
+from importlib.metadata import version
 from pathlib import Path
 
-from pkg_resources import get_distribution
+from sphinx.application import Sphinx
 
 CURRENT_DIR = Path(__file__).parent
 
@@ -25,12 +26,33 @@
 def make_pypi_svg(version: str) -> None:
     template: Path = CURRENT_DIR / "_static" / "pypi_template.svg"
     target: Path = CURRENT_DIR / "_static" / "pypi.svg"
-    with open(str(template), "r", encoding="utf8") as f:
+    with open(str(template), encoding="utf8") as f:
         svg: str = string.Template(f.read()).substitute(version=version)
     with open(str(target), "w", encoding="utf8") as f:
         f.write(svg)
 
 
+def replace_pr_numbers_with_links(content: str) -> str:
+    """Replaces all PR numbers with the corresponding GitHub link."""
+    return re.sub(r"#(\d+)", r"[#\1](https://github.com/psf/black/pull/\1)", content)
+
+
+def handle_include_read(
+    app: Sphinx,
+    relative_path: Path,
+    parent_docname: str,
+    content: list[str],
+) -> None:
+    """Handler for the include-read sphinx event."""
+    if parent_docname == "change_log":
+        content[0] = replace_pr_numbers_with_links(content[0])
+
+
+def setup(app: Sphinx) -> None:
+    """Sets up a minimal sphinx extension."""
+    app.connect("include-read", handle_include_read)
+
+
 # Necessary so Click doesn't hit an encode error when called by
 # sphinxcontrib-programoutput on Windows.
 os.putenv("pythonioencoding", "utf-8")
@@ -43,7 +65,7 @@ def make_pypi_svg(version: str) -> None:
 
 # Autopopulate version
 # The version, including alpha/beta/rc tags, but not commit hash and datestamps
-release = get_distribution("black").version.split("+")[0]
+release = version("black").split("+")[0]
 # The short X.Y version.
 version = release
 for sp in "abcfr":

docs/contributing/index.md

@@ -9,7 +9,6 @@ the_basics
 gauging_changes
 issue_triage
 release_process
-reference/reference_summary
 ```
 
 Welcome! Happy to see you willing to make the project better. Have you read the entire
@@ -42,9 +41,5 @@ This section covers the following topics:
 - {doc}`the_basics`
 - {doc}`gauging_changes`
 - {doc}`release_process`
-- {doc}`reference/reference_summary`
 
 For an overview on contributing to the _Black_, please checkout {doc}`the_basics`.
-
-If you need a reference of the functions, classes, etc. available to you while
-developing _Black_, there's the {doc}`reference/reference_summary` docs.

docs/contributing/reference/reference_classes.rst

@@ -1,234 +0,0 @@
-*Black* classes
-===============
-
-*Contents are subject to change.*
-
-Black Classes
-~~~~~~~~~~~~~~
-
-.. currentmodule:: black
-
-:class:`BracketTracker`
------------------------
-
-.. autoclass:: black.brackets.BracketTracker
-    :members:
-
-:class:`Line`
--------------
-
-.. autoclass:: black.lines.Line
-    :members:
-    :special-members: __str__, __bool__
-
-:class:`RHSResult`
--------------------------
-
-.. autoclass:: black.lines.RHSResult
-    :members:
-
-:class:`LinesBlock`
--------------------------
-
-.. autoclass:: black.lines.LinesBlock
-    :members:
-
-:class:`EmptyLineTracker`
--------------------------
-
-.. autoclass:: black.lines.EmptyLineTracker
-    :members:
-
-:class:`LineGenerator`
-----------------------
-
-.. autoclass:: black.linegen.LineGenerator
-    :show-inheritance:
-    :members:
-
-:class:`ProtoComment`
----------------------
-
-.. autoclass:: black.comments.ProtoComment
-    :members:
-
-:class:`Mode`
----------------------
-
-.. autoclass:: black.mode.Mode
-    :members:
-
-:class:`Report`
----------------
-
-.. autoclass:: black.report.Report
-    :members:
-    :special-members: __str__
-
-:class:`Ok`
----------------
-
-.. autoclass:: black.rusty.Ok
-    :show-inheritance:
-    :members:
-
-:class:`Err`
----------------
-
-.. autoclass:: black.rusty.Err
-    :show-inheritance:
-    :members:
-
-:class:`Visitor`
-----------------
-
-.. autoclass:: black.nodes.Visitor
-    :show-inheritance:
-    :members:
-
-:class:`StringTransformer`
-----------------------------
-
-.. autoclass:: black.trans.StringTransformer
-    :show-inheritance:
-    :members:
-
-:class:`CustomSplit`
-----------------------------
-
-.. autoclass:: black.trans.CustomSplit
-    :members:
-
-:class:`CustomSplitMapMixin`
------------------------------
-
-.. autoclass:: black.trans.CustomSplitMapMixin
-    :show-inheritance:
-    :members:
-
-:class:`StringMerger`
-----------------------
-
-.. autoclass:: black.trans.StringMerger
-    :show-inheritance:
-    :members:
-
-:class:`StringParenStripper`
------------------------------
-
-.. autoclass:: black.trans.StringParenStripper
-    :show-inheritance:
-    :members:
-
-:class:`BaseStringSplitter`
------------------------------
-
-.. autoclass:: black.trans.BaseStringSplitter
-    :show-inheritance:
-    :members:
-
-:class:`StringSplitter`
------------------------------
-
-.. autoclass:: black.trans.StringSplitter
-    :show-inheritance:
-    :members:
-
-:class:`StringParenWrapper`
------------------------------
-
-.. autoclass:: black.trans.StringParenWrapper
-    :show-inheritance:
-    :members:
-
-:class:`StringParser`
------------------------------
-
-.. autoclass:: black.trans.StringParser
-    :members:
-
-:class:`DebugVisitor`
-------------------------
-
-.. autoclass:: black.debug.DebugVisitor
-    :show-inheritance:
-    :members:
-
-:class:`Replacement`
-------------------------
-
-.. autoclass:: black.handle_ipynb_magics.Replacement
-    :members:
-
-:class:`CellMagic`
-------------------------
-
-.. autoclass:: black.handle_ipynb_magics.CellMagic
-    :members:
-
-:class:`CellMagicFinder`
-------------------------
-
-.. autoclass:: black.handle_ipynb_magics.CellMagicFinder
-    :show-inheritance:
-    :members:
-
-:class:`OffsetAndMagic`
-------------------------
-
-.. autoclass:: black.handle_ipynb_magics.OffsetAndMagic
-    :members:
-
-:class:`MagicFinder`
-------------------------
-
-.. autoclass:: black.handle_ipynb_magics.MagicFinder
-    :show-inheritance:
-    :members:
-
-:class:`Cache`
-------------------------
-
-.. autoclass:: black.cache.Cache
-    :show-inheritance:
-    :members:
-
-Enum Classes
-~~~~~~~~~~~~~
-
-Classes inherited from Python `Enum <https://docs.python.org/3/library/enum.html#enum.Enum>`_ class.
-
-:class:`Changed`
-----------------
-
-.. autoclass:: black.report.Changed
-    :show-inheritance:
-    :members:
-
-:class:`WriteBack`
-------------------
-
-.. autoclass:: black.WriteBack
-    :show-inheritance:
-    :members:
-
-:class:`TargetVersion`
-----------------------
-
-.. autoclass:: black.mode.TargetVersion
-    :show-inheritance:
-    :members:
-
-:class:`Feature`
-------------------
-
-.. autoclass:: black.mode.Feature
-    :show-inheritance:
-    :members:
-
-:class:`Preview`
-------------------
-
-.. autoclass:: black.mode.Preview
-    :show-inheritance:
-    :members:

docs/contributing/reference/reference_exceptions.rst

@@ -1,18 +0,0 @@
-*Black* exceptions
-==================
-
-*Contents are subject to change.*
-
-.. currentmodule:: black
-
-.. autoexception:: black.trans.CannotTransform
-
-.. autoexception:: black.linegen.CannotSplit
-
-.. autoexception:: black.brackets.BracketMatchError
-
-.. autoexception:: black.report.NothingChanged
-
-.. autoexception:: black.parsing.InvalidInput
-
-.. autoexception:: black.mode.Deprecated

docs/contributing/reference/reference_functions.rst

@@ -1,172 +0,0 @@
-*Black* functions
-=================
-
-*Contents are subject to change.*
-
-.. currentmodule:: black
-
-Assertions and checks
----------------------
-
-.. autofunction:: black.assert_equivalent
-
-.. autofunction:: black.assert_stable
-
-.. autofunction:: black.lines.can_be_split
-
-.. autofunction:: black.lines.can_omit_invisible_parens
-
-.. autofunction:: black.nodes.is_empty_tuple
-
-.. autofunction:: black.nodes.is_import
-
-.. autofunction:: black.lines.is_line_short_enough
-
-.. autofunction:: black.nodes.is_multiline_string
-
-.. autofunction:: black.nodes.is_one_tuple
-
-.. autofunction:: black.brackets.is_split_after_delimiter
-
-.. autofunction:: black.brackets.is_split_before_delimiter
-
-.. autofunction:: black.nodes.is_stub_body
-
-.. autofunction:: black.nodes.is_stub_suite
-
-.. autofunction:: black.nodes.is_vararg
-
-.. autofunction:: black.nodes.is_yield
-
-
-Formatting
-----------
-
-.. autofunction:: black.format_file_contents
-
-.. autofunction:: black.format_file_in_place
-
-.. autofunction:: black.format_stdin_to_stdout
-
-.. autofunction:: black.format_str
-
-.. autofunction:: black.reformat_one
-
-.. autofunction:: black.concurrency.schedule_formatting
-
-File operations
----------------
-
-.. autofunction:: black.dump_to_file
-
-.. autofunction:: black.find_project_root
-
-.. autofunction:: black.gen_python_files
-
-.. autofunction:: black.read_pyproject_toml
-
-Parsing
--------
-
-.. autofunction:: black.decode_bytes
-
-.. autofunction:: black.parsing.lib2to3_parse
-
-.. autofunction:: black.parsing.lib2to3_unparse
-
-Split functions
----------------
-
-.. autofunction:: black.linegen.bracket_split_build_line
-
-.. autofunction:: black.linegen.bracket_split_succeeded_or_raise
-
-.. autofunction:: black.linegen.delimiter_split
-
-.. autofunction:: black.linegen.left_hand_split
-
-.. autofunction:: black.linegen.right_hand_split
-
-.. autofunction:: black.linegen.standalone_comment_split
-
-.. autofunction:: black.linegen.transform_line
-
-Caching
--------
-
-.. autofunction:: black.cache.get_cache_dir
-
-.. autofunction:: black.cache.get_cache_file
-
-Utilities
----------
-
-.. py:function:: black.debug.DebugVisitor.show(code: str) -> None
-
-    Pretty-print the lib2to3 AST of a given string of `code`.
-
-.. autofunction:: black.concurrency.cancel
-
-.. autofunction:: black.nodes.child_towards
-
-.. autofunction:: black.nodes.container_of
-
-.. autofunction:: black.comments.convert_one_fmt_off_pair
-
-.. autofunction:: black.diff
-
-.. autofunction:: black.linegen.dont_increase_indentation
-
-.. autofunction:: black.numerics.format_float_or_int_string
-
-.. autofunction:: black.nodes.ensure_visible
-
-.. autofunction:: black.lines.enumerate_reversed
-
-.. autofunction:: black.comments.generate_comments
-
-.. autofunction:: black.comments.generate_ignored_nodes
-
-.. autofunction:: black.comments.is_fmt_on
-
-.. autofunction:: black.comments.children_contains_fmt_on
-
-.. autofunction:: black.nodes.first_leaf_of
-
-.. autofunction:: black.linegen.generate_trailers_to_omit
-
-.. autofunction:: black.get_future_imports
-
-.. autofunction:: black.comments.list_comments
-
-.. autofunction:: black.comments.make_comment
-
-.. autofunction:: black.linegen.maybe_make_parens_invisible_in_atom
-
-.. autofunction:: black.brackets.max_delimiter_priority_in_atom
-
-.. autofunction:: black.normalize_fmt_off
-
-.. autofunction:: black.numerics.normalize_numeric_literal
-
-.. autofunction:: black.comments.normalize_trailing_prefix
-
-.. autofunction:: black.strings.normalize_string_prefix
-
-.. autofunction:: black.strings.normalize_string_quotes
-
-.. autofunction:: black.linegen.normalize_invisible_parens
-
-.. autofunction:: black.nodes.preceding_leaf
-
-.. autofunction:: black.re_compile_maybe_verbose
-
-.. autofunction:: black.linegen.should_split_line
-
-.. autofunction:: black.concurrency.shutdown
-
-.. autofunction:: black.strings.sub_twice
-
-.. autofunction:: black.nodes.whitespace
-
-.. autofunction:: black.nodes.make_simple_prefix

docs/contributing/reference/reference_summary.rst

@@ -1,19 +0,0 @@
-Developer reference
-===================
-
-.. note::
-
-  As of June 2023, the documentation of *Black classes* and *Black exceptions*
-  has been updated to the latest available version.
-
-  The documentation of *Black functions* is quite outdated and has been neglected. Many
-  functions worthy of inclusion aren't documented. Contributions are appreciated!
-
-*Contents are subject to change.*
-
-.. toctree::
-   :maxdepth: 2
-
-   reference_classes
-   reference_functions
-   reference_exceptions

docs/contributing/the_basics.md

@@ -7,7 +7,14 @@ An overview on contributing to the _Black_ project.
 Development on the latest version of Python is preferred. You can use any operating
 system.
 
-Install development dependencies inside a virtual environment of your choice, for
+First clone the _Black_ repository:
+
+```console
+$ git clone https://github.com/psf/black.git
+$ cd black
+```
+
+Then install development dependencies inside a virtual environment of your choice, for
 example:
 
 ```console
@@ -16,7 +23,7 @@ $ source .venv/bin/activate # activation for linux and mac
 $ .venv\Scripts\activate # activation for windows
 
 (.venv)$ pip install -r test_requirements.txt
-(.venv)$ pip install -e .[d]
+(.venv)$ pip install -e ".[d]"
 (.venv)$ pre-commit install
 ```
 
@@ -48,13 +55,16 @@ Further examples of invoking the tests
 # Run tests on a specific python version
 (.venv)$ tox -e py39
 
-# pass arguments to pytest
+# Run an individual test
+(.venv)$ pytest -k <test name>
+
+# Pass arguments to pytest
 (.venv)$ tox -e py -- --no-cov
 
-# print full tree diff, see documentation below
+# Print full tree diff, see documentation below
 (.venv)$ tox -e py -- --print-full-tree
 
-# disable diff printing, see documentation below
+# Disable diff printing, see documentation below
 (.venv)$ tox -e py -- --print-tree-diff=False
 ```
 
@@ -99,16 +109,22 @@ default. To turn it off pass `--print-tree-diff=False`.
 `Black` has CI that will check for an entry corresponding to your PR in `CHANGES.md`. If
 you feel this PR does not require a changelog entry please state that in a comment and a
 maintainer can add a `skip news` label to make the CI pass. Otherwise, please ensure you
-have a line in the following format:
+have a line in the following format added below the appropriate header:
 
 ```md
 - `Black` is now more awesome (#X)
 ```
 
+<!---
+The Next PR Number link uses HTML because of a bug in MyST-Parser that double-escapes the ampersand, causing the query parameters to not be processed.
+MyST-Parser issue: https://github.com/executablebooks/MyST-Parser/issues/760
+MyST-Parser stalled fix PR: https://github.com/executablebooks/MyST-Parser/pull/929
+-->
+
 Note that X should be your PR number, not issue number! To workout X, please use
-[Next PR Number](https://ichard26.github.io/next-pr-number/?owner=psf&name=black). This
-is not perfect but saves a lot of release overhead as now the releaser does not need to
-go back and workout what to add to the `CHANGES.md` for each release.
+<a href="https://ichard26.github.io/next-pr-number/?owner=psf&name=black">Next PR
+Number</a>. This is not perfect but saves a lot of release overhead as now the releaser
+does not need to go back and workout what to add to the `CHANGES.md` for each release.
 
 ### Style Changes
 
@@ -116,7 +132,7 @@ If a change would affect the advertised code style, please modify the documentat
 _Black_ code style) to reflect that change. Patches that fix unintended bugs in
 formatting don't need to be mentioned separately though. If the change is implemented
 with the `--preview` flag, please include the change in the future style document
-instead and write the changelog entry under a dedicated "Preview changes" heading.
+instead and write the changelog entry under the dedicated "Preview style" heading.
 
 ### Docs Testing
 
@@ -124,17 +140,17 @@ If you make changes to docs, you can test they still build locally too.
 
 ```console
 (.venv)$ pip install -r docs/requirements.txt
-(.venv)$ pip install -e .[d]
+(.venv)$ pip install -e ".[d]"
 (.venv)$ sphinx-build -a -b html -W docs/ docs/_build/
 ```
 
 ## Hygiene
 
 If you're fixing a bug, add a test. Run it first to confirm it fails, then fix the bug,
-run it again to confirm it's really fixed.
+and run the test again to confirm it's really fixed.
 
-If adding a new feature, add a test. In fact, always add a test. But wait, before adding
-any large feature, first open an issue for us to discuss the idea first.
+If adding a new feature, add a test. In fact, always add a test. If adding a large
+feature, please first open an issue to discuss it beforehand.
 
 ## Finally
 

docs/faq.md

@@ -41,9 +41,10 @@ other tools, such as `# noqa`, may be moved by _Black_. See below for more detai
 Stable. _Black_ aims to enforce one style and one style only, with some room for
 pragmatism. See [The Black Code Style](the_black_code_style/index.md) for more details.
 
-Starting in 2022, the formatting output will be stable for the releases made in the same
-year (other than unintentional bugs). It is possible to opt-in to the latest formatting
-styles, using the `--preview` flag.
+Starting in 2022, the formatting output is stable for the releases made in the same year
+(other than unintentional bugs). At the beginning of every year, the first release will
+make changes to the stable style. It is possible to opt in to the latest formatting
+styles using the `--preview` flag.
 
 ## Why is my file not formatted?
 
@@ -76,26 +77,26 @@ following will not be formatted:
 - invalid syntax, as it can't be safely distinguished from automagics in the absence of
   a running `IPython` kernel.
 
-## Why are Flake8's E203 and W503 violated?
+## Why does Flake8 report warnings?
 
-Because they go against PEP 8. E203 falsely triggers on list
-[slices](the_black_code_style/current_style.md#slices), and adhering to W503 hinders
-readability because operators are misaligned. Disable W503 and enable the
-disabled-by-default counterpart W504. E203 should be disabled while changes are still
-[discussed](https://github.com/PyCQA/pycodestyle/issues/373).
+Some of Flake8's rules conflict with Black's style. We recommend disabling these rules.
+See [Using _Black_ with other tools](labels/why-pycodestyle-warnings).
 
 ## Which Python versions does Black support?
 
-Currently the runtime requires Python 3.8-3.11. Formatting is supported for files
-containing syntax from Python 3.3 to 3.11. We promise to support at least all Python
-versions that have not reached their end of life. This is the case for both running
-_Black_ and formatting code.
+_Black_ generally supports all Python versions supported by CPython (see
+[the Python devguide](https://devguide.python.org/versions/) for current information).
+We promise to support at least all Python versions that have not reached their end of
+life. This is the case for both running _Black_ and formatting code.
 
 Support for formatting Python 2 code was removed in version 22.0. While we've made no
 plans to stop supporting older Python 3 minor versions immediately, their support might
 also be removed some time in the future without a deprecation period.
 
-Runtime support for 3.7 was removed in version 23.7.0.
+`await`/`async` as soft keywords/indentifiers are no longer supported as of 25.2.0.
+
+Runtime support for 3.6 was removed in version 22.10.0, for 3.7 in version 23.7.0, and
+for 3.8 in version 24.10.0.
 
 ## Why does my linter or typechecker complain after I format my code?
 

docs/getting_started.md

@@ -16,9 +16,11 @@ Also, you can try out _Black_ online for minimal fuss on the
 
 ## Installation
 
-_Black_ can be installed by running `pip install black`. It requires Python 3.8+ to run.
+_Black_ can be installed by running `pip install black`. It requires Python 3.9+ to run.
 If you want to format Jupyter Notebooks, install with `pip install "black[jupyter]"`.
 
+If you use pipx, you can install Black with `pipx install black`.
+
 If you can't wait for the latest _hotness_ and want to install from GitHub, use:
 
 `pip install git+https://github.com/psf/black`

docs/guides/using_black_with_other_tools.md

@@ -134,10 +134,10 @@ profile = black
 
 </details>
 
-### Flake8
+### pycodestyle
 
-[Flake8](https://pypi.org/p/flake8/) is a code linter. It warns you of syntax errors,
-possible bugs, stylistic errors, etc. For the most part, Flake8 follows
+[pycodestyle](https://pycodestyle.pycqa.org/) is a code linter. It warns you of syntax
+errors, possible bugs, stylistic errors, etc. For the most part, pycodestyle follows
 [PEP 8](https://www.python.org/dev/peps/pep-0008/) when warning about stylistic errors.
 There are a few deviations that cause incompatibilities with _Black_.
 
@@ -145,67 +145,115 @@ There are a few deviations that cause incompatibilities with _Black_.
 
 ```
 max-line-length = 88
-extend-ignore = E203
+ignore = E203,E701
 ```
 
+(labels/why-pycodestyle-warnings)=
+
 #### Why those options above?
 
+##### `max-line-length`
+
+As with isort, pycodestyle should be configured to allow lines up to the length limit of
+`88`, _Black_'s default.
+
+##### `E203`
+
 In some cases, as determined by PEP 8, _Black_ will enforce an equal amount of
-whitespace around slice operators. Due to this, Flake8 will raise
-`E203 whitespace before ':'` warnings. Since this warning is not PEP 8 compliant, Flake8
-should be configured to ignore it via `extend-ignore = E203`.
+whitespace around slice operators. Due to this, pycodestyle will raise
+`E203 whitespace before ':'` warnings. Since this warning is not PEP 8 compliant, it
+should be disabled.
+
+##### `E701` / `E704`
+
+_Black_ will collapse implementations of classes and functions consisting solely of `..`
+to a single line. This matches how such examples are formatted in PEP 8. It remains true
+that in all other cases Black will prevent multiple statements on the same line, in
+accordance with PEP 8 generally discouraging this.
+
+However, `pycodestyle` does not mirror this logic and may raise
+`E701 multiple statements on one line (colon)` in this situation. Its
+disabled-by-default `E704 multiple statements on one line (def)` rule may also raise
+warnings and should not be enabled.
+
+##### `W503`
 
 When breaking a line, _Black_ will break it before a binary operator. This is compliant
 with PEP 8 as of
 [April 2016](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b#diff-64ec08cc46db7540f18f2af46037f599).
 There's a disabled-by-default warning in Flake8 which goes against this PEP 8
 recommendation called `W503 line break before binary operator`. It should not be enabled
-in your configuration.
-
-Also, as like with isort, flake8 should be configured to allow lines up to the length
-limit of `88`, _Black_'s default. This explains `max-line-length = 88`.
+in your configuration. You can use its counterpart
+`W504 line break after binary operator` instead.
 
 #### Formats
 
 <details>
-<summary>.flake8</summary>
+<summary>setup.cfg, .pycodestyle, tox.ini</summary>
 
 ```ini
-[flake8]
+[pycodestyle]
 max-line-length = 88
-extend-ignore = E203, E704
+ignore = E203,E701
 ```
 
 </details>
 
-<details>
-<summary>setup.cfg</summary>
+### Flake8
 
-```ini
+[Flake8](https://pypi.org/p/flake8/) is a wrapper around multiple linters, including
+pycodestyle. As such, it has many of the same issues.
+
+#### Bugbear
+
+It's recommended to use [the Bugbear plugin](https://github.com/PyCQA/flake8-bugbear)
+and enable
+[its B950 check](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings#:~:text=you%20expect%20it.-,B950,-%3A%20Line%20too%20long)
+instead of using Flake8's E501, because it aligns with
+[Black's 10% rule](labels/line-length).
+
+Install Bugbear and use the following config:
+
+```
 [flake8]
-max-line-length = 88
-extend-ignore = E203
+max-line-length = 80
+extend-select = B950
+extend-ignore = E203,E501,E701
 ```
 
-</details>
+#### Minimal Configuration
+
+In cases where you can't or don't want to install Bugbear, you can use this minimally
+compatible config:
+
+```
+[flake8]
+max-line-length = 88
+extend-ignore = E203,E701
+```
+
+#### Why those options above?
+
+See [the pycodestyle section](labels/why-pycodestyle-warnings) above.
+
+#### Formats
 
 <details>
-<summary>tox.ini</summary>
+<summary>.flake8, setup.cfg, tox.ini</summary>
 
 ```ini
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701
 ```
 
 </details>
 
 ### Pylint
 
-[Pylint](https://pypi.org/p/pylint/) is also a code linter like Flake8. It has the same
-checks as flake8 and more. In particular, it has more formatting checks regarding style
-conventions like variable naming. With so many checks, Pylint is bound to have some
-mixed feelings about _Black_'s formatting style.
+[Pylint](https://pypi.org/p/pylint/) is also a code linter like Flake8. It has many of
+the same checks as Flake8 and more. It particularly has more formatting checks regarding
+style conventions like variable naming.
 
 #### Configuration
 
@@ -252,35 +300,3 @@ max-line-length = "88"
 ```
 
 </details>
-
-### pycodestyle
-
-[pycodestyle](https://pycodestyle.pycqa.org/) is also a code linter like Flake8.
-
-#### Configuration
-
-```
-max-line-length = 88
-ignore = E203
-```
-
-#### Why those options above?
-
-pycodestyle should be configured to only complain about lines that surpass `88`
-characters via `max_line_length = 88`.
-
-See
-[Why are Flake8’s E203 and W503 violated?](https://black.readthedocs.io/en/stable/faq.html#why-are-flake8-s-e203-and-w503-violated)
-
-#### Formats
-
-<details>
-<summary>setup.cfg</summary>
-
-```cfg
-[pycodestyle]
-ignore = E203
-max_line_length = 88
-```
-
-</details>

docs/integrations/editors.md

@@ -236,7 +236,7 @@ Configuration:
 
 #### Installation
 
-This plugin **requires Vim 7.0+ built with Python 3.8+ support**. It needs Python 3.8 to
+This plugin **requires Vim 7.0+ built with Python 3.9+ support**. It needs Python 3.9 to
 be able to run _Black_ inside the Vim process which is much faster than calling an
 external command.
 
@@ -432,4 +432,4 @@ hook global WinSetOption filetype=python %{
 
 ## Thonny
 
-Use [Thonny-black-code-format](https://github.com/Franccisco/thonny-black-code-format).
+Use [Thonny-black-formatter](https://pypi.org/project/thonny-black-formatter/).

docs/integrations/github_actions.md

@@ -24,7 +24,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: psf/black@stable
 ```
 
@@ -32,12 +32,15 @@ We recommend the use of the `@stable` tag, but per version tags also exist if yo
 that. Note that the action's version you select is independent of the version of _Black_
 the action will use.
 
-The version of _Black_ the action will use can be configured via `version`. This can be
-any
+The version of _Black_ the action will use can be configured via `version` or read from
+the `pyproject.toml` file. `version` can be any
 [valid version specifier](https://packaging.python.org/en/latest/glossary/#term-Version-Specifier)
-or just the version number if you want an exact version. The action defaults to the
-latest release available on PyPI. Only versions available from PyPI are supported, so no
-commit SHAs or branch names.
+or just the version number if you want an exact version. To read the version from the
+`pyproject.toml` file instead, set `use_pyproject` to `true`. This will first look into
+the `tool.black.required-version` field, then the `dependency-groups` table, then the
+`project.dependencies` array and finally the `project.optional-dependencies` table. The
+action defaults to the latest release available on PyPI. Only versions available from
+PyPI are supported, so no commit SHAs or branch names.
 
 If you want to include Jupyter Notebooks, _Black_ must be installed with the `jupyter`
 extra. Installing the extra and including Jupyter Notebook files can be configured via
@@ -70,3 +73,18 @@ If you want to match versions covered by Black's
     src: "./src"
     version: "~= 22.0"
 ```
+
+If you want to read the version from `pyproject.toml`, set `use_pyproject` to `true`.
+Note that this requires Python >= 3.11, so using the setup-python action may be
+required, for example:
+
+```yaml
+- uses: actions/setup-python@v5
+  with:
+    python-version: "3.13"
+- uses: psf/black@stable
+  with:
+    options: "--check --verbose"
+    src: "./src"
+    use_pyproject: true
+```

docs/integrations/source_version_control.md

@@ -8,7 +8,7 @@ Use [pre-commit](https://pre-commit.com/). Once you
 repos:
   # Using this mirror lets us use mypyc-compiled black, which is about 2x faster
   - repo: https://github.com/psf/black-pre-commit-mirror
-    rev: 23.12.0
+    rev: 25.1.0
     hooks:
       - id: black
         # It is recommended to specify the latest version of Python
@@ -35,7 +35,7 @@ include Jupyter Notebooks. To use this hook, simply replace the hook's `id: blac
 repos:
   # Using this mirror lets us use mypyc-compiled black, which is about 2x faster
   - repo: https://github.com/psf/black-pre-commit-mirror
-    rev: 23.12.0
+    rev: 25.1.0
     hooks:
       - id: black-jupyter
         # It is recommended to specify the latest version of Python

docs/requirements.txt

@@ -1,9 +1,9 @@
 # Used by ReadTheDocs; pinned requirements for stability.
 
-myst-parser==2.0.0
-Sphinx==7.2.6
+myst-parser==4.0.1
+Sphinx==8.2.3
 # Older versions break Sphinx even though they're declared to be supported.
-docutils==0.20.1
-sphinxcontrib-programoutput==0.17
+docutils==0.21.2
+sphinxcontrib-programoutput==0.18
 sphinx_copybutton==0.5.2
-furo==2023.9.10
+furo==2024.8.6

docs/the_black_code_style/current_style.md

@@ -143,7 +143,7 @@ significantly shorter files than sticking with 80 (the most popular), or even 79
 by the standard library). In general,
 [90-ish seems like the wise choice](https://youtu.be/wf-BqAjZb8M?t=260).
 
-If you're paid by the line of code you write, you can pass `--line-length` with a lower
+If you're paid by the lines of code you write, you can pass `--line-length` with a lower
 number. _Black_ will try to respect that. However, sometimes it won't be able to without
 breaking other rules. In those rare cases, auto-formatted code will exceed your allotted
 limit.
@@ -153,35 +153,10 @@ harder to work with line lengths exceeding 100 characters. It also adversely aff
 side-by-side diff review on typical screen resolutions. Long lines also make it harder
 to present code neatly in documentation or talk slides.
 
-#### Flake8
+#### Flake8 and other linters
 
-If you use Flake8, you have a few options:
-
-1. Recommended is using [Bugbear](https://github.com/PyCQA/flake8-bugbear) and enabling
-   its B950 check instead of using Flake8's E501, because it aligns with Black's 10%
-   rule. Install Bugbear and use the following config:
-
-   ```ini
-   [flake8]
-   max-line-length = 80
-   ...
-   select = C,E,F,W,B,B950
-   extend-ignore = E203, E501, E704
-   ```
-
-   The rationale for B950 is explained in
-   [Bugbear's documentation](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings).
-
-2. For a minimally compatible config:
-
-   ```ini
-   [flake8]
-   max-line-length = 88
-   extend-ignore = E203, E704
-   ```
-
-An explanation of why E203 is disabled can be found in the [Slices section](#slices) of
-this page.
+See [Using _Black_ with other tools](../guides/using_black_with_other_tools.md) about
+linter compatibility.
 
 ### Empty lines
 
@@ -191,44 +166,35 @@ that in-function vertical whitespace should only be used sparingly.
 _Black_ will allow single empty lines inside functions, and single and double empty
 lines on module level left by the original editors, except when they're within
 parenthesized expressions. Since such expressions are always reformatted to fit minimal
-space, this whitespace is lost. The other exception is that it will remove any empty
-lines immediately following a statement that introduces a new indentation level.
+space, this whitespace is lost.
 
 ```python
 # in:
 
-def foo():
+def function(
+    some_argument: int,
 
-    print("All the newlines above me should be deleted!")
+    other_argument: int = 5,
+) -> EmptyLineInParenWillBeDeleted:
 
 
-if condition:
 
-    print("No newline above me!")
-
-    print("There is a newline above me, and that's OK!")
-
-
-class Point:
-
-    x: int
-    y: int
+    print("One empty line above me will be kept!")
 
+def this_is_okay_too():
+    print("No empty line here")
 # out:
 
-def foo():
-    print("All the newlines above me should be deleted!")
+def function(
+    some_argument: int,
+    other_argument: int = 5,
+) -> EmptyLineInParenWillBeDeleted:
+
+    print("One empty line above me will be kept!")
 
 
-if condition:
-    print("No newline above me!")
-
-    print("There is a newline above me, and that's OK!")
-
-
-class Point:
-    x: int
-    y: int
+def this_is_okay_too():
+    print("No empty line here")
 ```
 
 It will also insert proper spacing before and after function definitions. It's one line
@@ -284,6 +250,11 @@ exception of [capital "R" prefixes](#rstrings-and-rstrings), unicode literal mar
 (`u`) are removed because they are meaningless in Python 3, and in the case of multiple
 characters "r" is put first as in spoken language: "raw f-string".
 
+Another area where Python allows multiple ways to format a string is escape sequences.
+For example, `"\uabcd"` and `"\uABCD"` evaluate to the same string. _Black_ normalizes
+such escape sequences to lowercase, but uses uppercase for `\N` named character escapes,
+such as `"\N{MEETEI MAYEK LETTER HUK}"`.
+
 The main reason to standardize on a single form of quotes is aesthetics. Having one kind
 of quotes everywhere reduces reader distraction. It will also enable a future version of
 _Black_ to merge consecutive string literals that ended up on the same line (see
@@ -449,6 +420,12 @@ file that are not enforced yet but might be in a future version of the formatter
 _Black_ will normalize line endings (`\n` or `\r\n`) based on the first line ending of
 the file.
 
+### Form feed characters
+
+_Black_ will retain form feed characters on otherwise empty lines at the module level.
+Only one form feed is retained for a group of consecutive empty lines. Where there are
+two empty lines in a row, the form feed is placed on the second line.
+
 ## Pragmatism
 
 Early versions of _Black_ used to be absolutist in some respects. They took after its

docs/the_black_code_style/future_style.md

@@ -1,94 +1,49 @@
 # The (future of the) Black code style
 
-```{warning}
-Changes to this document often aren't tied and don't relate to releases of
-_Black_. It's recommended that you read the latest version available.
-```
-
-## Using backslashes for with statements
-
-[Backslashes are bad and should be never be used](labels/why-no-backslashes) however
-there is one exception: `with` statements using multiple context managers. Before Python
-3.9 Python's grammar does not allow organizing parentheses around the series of context
-managers.
-
-We don't want formatting like:
-
-```py3
-with make_context_manager1() as cm1, make_context_manager2() as cm2, make_context_manager3() as cm3, make_context_manager4() as cm4:
-    ...  # nothing to split on - line too long
-```
-
-So _Black_ will, when we implement this, format it like this:
-
-```py3
-with \
-     make_context_manager1() as cm1, \
-     make_context_manager2() as cm2, \
-     make_context_manager3() as cm3, \
-     make_context_manager4() as cm4 \
-:
-    ...  # backslashes and an ugly stranded colon
-```
-
-Although when the target version is Python 3.9 or higher, _Black_ uses parentheses
-instead in `--preview` mode (see below) since they're allowed in Python 3.9 and higher.
-
-An alternative to consider if the backslashes in the above formatting are undesirable is
-to use {external:py:obj}`contextlib.ExitStack` to combine context managers in the
-following way:
-
-```python
-with contextlib.ExitStack() as exit_stack:
-    cm1 = exit_stack.enter_context(make_context_manager1())
-    cm2 = exit_stack.enter_context(make_context_manager2())
-    cm3 = exit_stack.enter_context(make_context_manager3())
-    cm4 = exit_stack.enter_context(make_context_manager4())
-    ...
-```
+## Preview style
 
 (labels/preview-style)=
 
-## Preview style
-
 Experimental, potentially disruptive style changes are gathered under the `--preview`
 CLI flag. At the end of each year, these changes may be adopted into the default style,
 as described in [The Black Code Style](index.md). Because the functionality is
 experimental, feedback and issue reports are highly encouraged!
 
-### Improved string processing
+In the past, the preview style included some features with known bugs, so that we were
+unable to move these features to the stable style. Therefore, such features are now
+moved to the `--unstable` style. All features in the `--preview` style are expected to
+make it to next year's stable style; features in the `--unstable` style will be
+stabilized only if issues with them are fixed. If bugs are discovered in a `--preview`
+feature, it is demoted to the `--unstable` style. To avoid thrash when a feature is
+demoted from the `--preview` to the `--unstable` style, users can use the
+`--enable-unstable-feature` flag to enable specific unstable features.
 
-_Black_ will split long string literals and merge short ones. Parentheses are used where
-appropriate. When split, parts of f-strings that don't need formatting are converted to
-plain strings. User-made splits are respected when they do not exceed the line length
-limit. Line continuation backslashes are converted into parenthesized strings.
-Unnecessary parentheses are stripped. The stability and status of this feature is
-tracked in [this issue](https://github.com/psf/black/issues/2188).
+(labels/preview-features)=
 
-### Improved line breaks
+Currently, the following features are included in the preview style:
 
-For assignment expressions, _Black_ now prefers to split and wrap the right side of the
-assignment instead of left side. For example:
+- `always_one_newline_after_import`: Always force one blank line after import
+  statements, except when the line after the import is a comment or an import statement
+- `wrap_long_dict_values_in_parens`: Add parentheses around long values in dictionaries
+  ([see below](labels/wrap-long-dict-values))
+- `fix_fmt_skip_in_one_liners`: Fix `# fmt: skip` behaviour on one-liner declarations,
+  such as `def foo(): return "mock"  # fmt: skip`, where previously the declaration
+  would have been incorrectly collapsed.
 
-```python
-some_dict[
-    "with_a_long_key"
-] = some_looooooooong_module.some_looooooooooooooong_function_name(
-    first_argument, second_argument, third_argument
-)
-```
+(labels/unstable-features)=
 
-will be changed to:
+The unstable style additionally includes the following features:
 
-```python
-some_dict["with_a_long_key"] = (
-    some_looooooooong_module.some_looooooooooooooong_function_name(
-        first_argument, second_argument, third_argument
-    )
-)
-```
+- `string_processing`: split long string literals and related changes
+  ([see below](labels/string-processing))
+- `multiline_string_handling`: more compact formatting of expressions involving
+  multiline strings ([see below](labels/multiline-string-handling))
+- `hug_parens_with_braces_and_square_brackets`: more compact formatting of nested
+  brackets ([see below](labels/hug-parens))
 
-### Improved parentheses management
+(labels/wrap-long-dict-values)=
+
+### Improved parentheses management in dicts
 
 For dict literals with long values, they are now wrapped in parentheses. Unnecessary
 parentheses are now removed. For example:
@@ -113,6 +68,8 @@ my_dict = {
 }
 ```
 
+(labels/hug-parens)=
+
 ### Improved multiline dictionary and list indentation for sole function parameter
 
 For better readability and less verticality, _Black_ now pairs parentheses ("(", ")")
@@ -185,6 +142,20 @@ foo(
 )
 ```
 
+(labels/string-processing)=
+
+### Improved string processing
+
+_Black_ will split long string literals and merge short ones. Parentheses are used where
+appropriate. When split, parts of f-strings that don't need formatting are converted to
+plain strings. f-strings will not be merged if they contain internal quotes and it would
+change their quotation mark style. User-made splits are respected when they do not
+exceed the line length limit. Line continuation backslashes are converted into
+parenthesized strings. Unnecessary parentheses are stripped. The stability and status of
+this feature istracked in [this issue](https://github.com/psf/black/issues/2188).
+
+(labels/multiline-string-handling)=
+
 ### Improved multiline string handling
 
 _Black_ is smarter when formatting multiline strings, especially in function arguments,
@@ -296,14 +267,3 @@ s = (  # Top comment
     # Bottom comment
 )
 ```
-
-=======
-
-### Form feed characters
-
-_Black_ will now retain form feed characters on otherwise empty lines at the module
-level. Only one form feed is retained for a group of consecutive empty lines. Where
-there are two empty lines in a row, the form feed will be placed on the second line.
-
-_Black_ already retained form feed literals inside a comment or inside a string. This
-remains the case.

docs/the_black_code_style/index.md

@@ -42,9 +42,11 @@ _Black_:
   enabled by newer Python language syntax as well as due to improvements in the
   formatting logic.
 
-- The `--preview` flag is exempt from this policy. There are no guarantees around the
-  stability of the output with that flag passed into _Black_. This flag is intended for
-  allowing experimentation with the proposed changes to the _Black_ code style.
+- The `--preview` and `--unstable` flags are exempt from this policy. There are no
+  guarantees around the stability of the output with these flags passed into _Black_.
+  They are intended for allowing experimentation with proposed changes to the _Black_
+  code style. The `--preview` style at the end of a year should closely match the stable
+  style for the next year, but we may always make changes.
 
 Documentation for both the current and future styles can be found:
 

docs/usage_and_configuration/black_as_a_server.md

@@ -62,6 +62,12 @@ The headers controlling how source code is formatted are:
 - `X-Preview`: corresponds to the `--preview` command line flag. If present and its
   value is not an empty string, experimental and potentially disruptive style changes
   will be used.
+- `X-Unstable`: corresponds to the `--unstable` command line flag. If present and its
+  value is not an empty string, experimental style changes that are known to be buggy
+  will be used.
+- `X-Enable-Unstable-Feature`: corresponds to the `--enable-unstable-feature` flag. The
+  contents of the flag must be a comma-separated list of unstable features to be
+  enabled. Example: `X-Enable-Unstable-Feature: feature1, feature2`.
 - `X-Fast-Or-Safe`: if set to `fast`, `blackd` will act as _Black_ does when passed the
   `--fast` command line flag.
 - `X-Python-Variant`: if set to `pyi`, `blackd` will act as _Black_ does when passed the

docs/usage_and_configuration/black_docker_image.md

@@ -8,16 +8,16 @@ _Black_ images with the following tags are available:
 - release numbers, e.g. `21.5b2`, `21.6b0`, `21.7b0` etc.\
   ℹ Recommended for users who want to use a particular version of _Black_.
 - `latest_release` - tag created when a new version of _Black_ is released.\
-  ℹ Recommended for users who want to use released versions of _Black_. It maps to [the latest release](https://github.com/psf/black/releases/latest)
-  of _Black_.
+  ℹ Recommended for users who want to use released versions of _Black_. It maps to
+  [the latest release](https://github.com/psf/black/releases/latest) of _Black_.
 - `latest_prerelease` - tag created when a new alpha (prerelease) version of _Black_ is
   released.\
-  ℹ Recommended for users who want to preview or test alpha versions of _Black_. Note that
-  the most recent release may be newer than any prerelease, because no prereleases are created
-  before most releases.
+  ℹ Recommended for users who want to preview or test alpha versions of _Black_. Note
+  that the most recent release may be newer than any prerelease, because no prereleases
+  are created before most releases.
 - `latest` - tag used for the newest image of _Black_.\
-  ℹ Recommended for users who always want to use the latest version of _Black_, even before
-  it is released.
+  ℹ Recommended for users who always want to use the latest version of _Black_, even
+  before it is released.
 
 There is one more tag used for _Black_ Docker images - `latest_non_release`. It is
 created for all unreleased

docs/usage_and_configuration/the_basics.md

@@ -70,17 +70,17 @@ See also [the style documentation](labels/line-length).
 
 Python versions that should be supported by Black's output. You can run `black --help`
 and look for the `--target-version` option to see the full list of supported versions.
-You should include all versions that your code supports. If you support Python 3.8
-through 3.11, you should write:
+You should include all versions that your code supports. If you support Python 3.11
+through 3.13, you should write:
 
 ```console
-$ black -t py38 -t py39 -t py310 -t py311
+$ black -t py311 -t py312 -t py313
 ```
 
 In a [configuration file](#configuration-via-a-file), you can write:
 
 ```toml
-target-version = ["py38", "py39", "py310", "py311"]
+target-version = ["py311", "py312", "py313"]
 ```
 
 By default, Black will infer target versions from the project metadata in
@@ -144,9 +144,34 @@ magic trailing comma is ignored.
 
 #### `--preview`
 
-Enable potentially disruptive style changes that may be added to Black's main
-functionality in the next major release. Read more about
-[our preview style](labels/preview-style).
+Enable potentially disruptive style changes that we expect to add to Black's main
+functionality in the next major release. Use this if you want a taste of what next
+year's style will look like.
+
+Read more about [our preview style](labels/preview-style).
+
+There is no guarantee on the code style produced by this flag across releases.
+
+#### `--unstable`
+
+Enable all style changes in `--preview`, plus additional changes that we would like to
+make eventually, but that have known issues that need to be fixed before they can move
+back to the `--preview` style. Use this if you want to experiment with these changes and
+help fix issues with them.
+
+There is no guarantee on the code style produced by this flag across releases.
+
+#### `--enable-unstable-feature`
+
+Enable specific features from the `--unstable` style. See
+[the preview style documentation](labels/unstable-features) for the list of supported
+features. This flag can only be used when `--preview` is enabled. Users are encouraged
+to use this flag if they use `--preview` style and a feature that affects their code is
+moved from the `--preview` to the `--unstable` style, but they want to avoid the thrash
+from undoing this change.
+
+There are no guarantees on the behavior of these features, or even their existence,
+across releases.
 
 (labels/exit-code)=
 
@@ -158,6 +183,9 @@ Don't write the files back, just return the status. _Black_ will exit with:
 - code 1 if some files would be reformatted; or
 - code 123 if there was an internal error
 
+If used in combination with `--quiet` then only the exit code will be returned, unless
+there was an internal error.
+
 ```console
 $ black test.py --check
 All done! ✨ 🍰 ✨
@@ -241,8 +269,8 @@ configuration file for consistent results across environments.
 
 ```console
 $ black --version
-black, 23.12.0 (compiled: yes)
-$ black --required-version 23.12.0 -c "format = 'this'"
+black, 25.1.0 (compiled: yes)
+$ black --required-version 25.1.0 -c "format = 'this'"
 format = "this"
 $ black --required-version 31.5b2 -c "still = 'beta?!'"
 Oh no! 💥 💔 💥 The required version does not match the running version!
@@ -268,6 +296,11 @@ recursive searches. An empty value means no paths are excluded. Use forward slas
 directories on all platforms (Windows, too). By default, Black also ignores all paths
 listed in `.gitignore`. Changing this value will override all default exclusions.
 
+If the regular expression contains newlines, it is treated as a
+[verbose regular expression](https://docs.python.org/3/library/re.html#re.VERBOSE). This
+is typically useful when setting these options in a `pyproject.toml` configuration file;
+see [Configuration format](#configuration-format) for more information.
+
 #### `--extend-exclude`
 
 Like `--exclude`, but adds additional files and directories on top of the default values
@@ -333,7 +366,7 @@ You can check the version of _Black_ you have installed using the `--version` fl
 
 ```console
 $ black --version
-black, 23.12.0
+black, 25.1.0
 ```
 
 #### `--config`
@@ -426,10 +459,11 @@ of tools like [Poetry](https://python-poetry.org/),
 
 ### Where _Black_ looks for the file
 
-By default _Black_ looks for `pyproject.toml` starting from the common base directory of
-all files and directories passed on the command line. If it's not there, it looks in
-parent directories. It stops looking when it finds the file, or a `.git` directory, or a
-`.hg` directory, or the root of the file system, whichever comes first.
+By default _Black_ looks for `pyproject.toml` containing a `[tool.black]` section
+starting from the common base directory of all files and directories passed on the
+command line. If it's not there, it looks in parent directories. It stops looking when
+it finds the file, or a `.git` directory, or a `.hg` directory, or the root of the file
+system, whichever comes first.
 
 If you're formatting standard input, _Black_ will look for configuration starting from
 the current working directory.
@@ -444,9 +478,10 @@ operating system, this configuration file should be stored as:
   `XDG_CONFIG_HOME` environment variable is not set)
 
 Note that these are paths to the TOML file itself (meaning that they shouldn't be named
-as `pyproject.toml`), not directories where you store the configuration. Here, `~`
-refers to the path to your home directory. On Windows, this will be something like
-`C:\\Users\UserName`.
+as `pyproject.toml`), not directories where you store the configuration (i.e.,
+`black`/`.black` is the file to create and add your configuration options to, in the
+`~/.config/` directory). Here, `~` refers to the path to your home directory. On
+Windows, this will be something like `C:\\Users\UserName`.
 
 You can also explicitly specify the path to a particular file that you want with
 `--config`. In this situation _Black_ will not look for any other file.

gallery/gallery.py

@@ -7,15 +7,16 @@
 import venv
 import zipfile
 from argparse import ArgumentParser, Namespace
+from collections.abc import Generator
 from concurrent.futures import ThreadPoolExecutor
 from functools import lru_cache, partial
 from pathlib import Path
-from typing import Generator, List, NamedTuple, Optional, Tuple, Union, cast
+from typing import NamedTuple, Optional, Union, cast
 from urllib.request import urlopen, urlretrieve
 
 PYPI_INSTANCE = "https://pypi.org/pypi"
 PYPI_TOP_PACKAGES = (
-    "https://hugovk.github.io/top-pypi-packages/top-pypi-packages-30-days.min.json"
+    "https://hugovk.github.io/top-pypi-packages/top-pypi-packages.min.json"
 )
 INTERNAL_BLACK_REPO = f"{tempfile.gettempdir()}/__black"
 
@@ -54,7 +55,7 @@ def get_pypi_download_url(package: str, version: Optional[str]) -> str:
     return cast(str, source["url"])
 
 
-def get_top_packages() -> List[str]:
+def get_top_packages() -> list[str]:
     with urlopen(PYPI_TOP_PACKAGES) as page:
         result = json.load(page)
 
@@ -150,7 +151,7 @@ def git_switch_branch(
     subprocess.run(args, cwd=repo)
 
 
-def init_repos(options: Namespace) -> Tuple[Path, ...]:
+def init_repos(options: Namespace) -> tuple[Path, ...]:
     options.output.mkdir(exist_ok=True)
 
     if options.top_packages:
@@ -206,7 +207,7 @@ def format_repo_with_version(
     git_switch_branch(black_version.version, repo=black_repo)
     git_switch_branch(current_branch, repo=repo, new=True, from_branch=from_branch)
 
-    format_cmd: List[Union[Path, str]] = [
+    format_cmd: list[Union[Path, str]] = [
         black_runner(black_version.version, black_repo),
         (black_repo / "black.py").resolve(),
         ".",
@@ -222,7 +223,7 @@ def format_repo_with_version(
     return current_branch
 
 
-def format_repos(repos: Tuple[Path, ...], options: Namespace) -> None:
+def format_repos(repos: tuple[Path, ...], options: Namespace) -> None:
     black_versions = tuple(
         BlackVersion(*version.split(":")) for version in options.versions
     )

plugin/black.vim

@@ -21,7 +21,7 @@ endif
 
 if v:version < 700 || !has('python3')
     func! __BLACK_MISSING()
-        echo "The black.vim plugin requires vim7.0+ with Python 3.6 support."
+        echo "The black.vim plugin requires vim7.0+ with Python 3.9 support."
     endfunc
     command! Black :call __BLACK_MISSING()
     command! BlackUpgrade :call __BLACK_MISSING()
@@ -72,12 +72,11 @@ endif
 
 function BlackComplete(ArgLead, CmdLine, CursorPos)
   return [
-\    'target_version=py27',
-\    'target_version=py36',
-\    'target_version=py37',
-\    'target_version=py38',
 \    'target_version=py39',
 \    'target_version=py310',
+\    'target_version=py311',
+\    'target_version=py312',
+\    'target_version=py313',
 \  ]
 endfunction
 

pyproject.toml

@@ -7,32 +7,34 @@
 
 [tool.black]
 line-length = 88
-target-version = ['py38']
+target-version = ['py39']
 include = '\.pyi?$'
 extend-exclude = '''
 /(
   # The following are specific to Black, you probably don't want those.
-  tests/data
-  | profiling
-)/
+  tests/data/
+  | profiling/
+  | scripts/generate_schema.py  # Uses match syntax
+)
 '''
-# We use preview style for formatting Black itself. If you
-# want stable formatting across releases, you should keep
-# this off.
-preview = true
+# We use the unstable style for formatting Black itself. If you
+# want bug-free formatting, you should keep this off. If you want
+# stable formatting across releases, you should also keep `preview = true`
+# (which is implied by this flag) off.
+unstable = true
 
 # Build system information and other project-specific configuration below.
 # NOTE: You don't need this in your own Black configuration.
 
 [build-system]
-requires = ["hatchling>=1.8.0", "hatch-vcs", "hatch-fancy-pypi-readme"]
+requires = ["hatchling>=1.20.0", "hatch-vcs", "hatch-fancy-pypi-readme"]
 build-backend = "hatchling.build"
 
 [project]
 name = "black"
 description = "The uncompromising code formatter."
-license = { text = "MIT" }
-requires-python = ">=3.8"
+license = "MIT"
+requires-python = ">=3.9"
 authors = [
   { name = "Łukasz Langa", email = "lukasz@langa.pl" },
 ]
@@ -53,11 +55,11 @@ classifiers = [
   "Operating System :: OS Independent",
   "Programming Language :: Python",
   "Programming Language :: Python :: 3 :: Only",
-  "Programming Language :: Python :: 3.8",
   "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
   "Topic :: Software Development :: Libraries :: Python Modules",
   "Topic :: Software Development :: Quality Assurance",
 ]
@@ -67,6 +69,7 @@ dependencies = [
   "packaging>=22.0",
   "pathspec>=0.9.0",
   "platformdirs>=2",
+  "pytokens>=0.1.10",
   "tomli>=1.1.0; python_version < '3.11'",
   "typing_extensions>=4.0.1; python_version < '3.11'",
 ]
@@ -75,10 +78,7 @@ dynamic = ["readme", "version"]
 [project.optional-dependencies]
 colorama = ["colorama>=0.4.3"]
 uvloop = ["uvloop>=0.15.2"]
-d = [
-  "aiohttp>=3.7.4; sys_platform != 'win32' or implementation_name != 'pypy'",
-  "aiohttp>=3.7.4, !=3.9.0; sys_platform == 'win32' and implementation_name == 'pypy'",
-]
+d = ["aiohttp>=3.10"]
 jupyter = [
   "ipython>=7.8.0",
   "tokenize-rt>=3.2.0",
@@ -88,9 +88,14 @@ jupyter = [
 black = "black:patched_main"
 blackd = "blackd:patched_main [d]"
 
+[project.entry-points."validate_pyproject.tool_schema"]
+black = "black.schema:get_schema"
+
 [project.urls]
+Documentation = "https://black.readthedocs.io/"
 Changelog = "https://github.com/psf/black/blob/main/CHANGES.md"
-Homepage = "https://github.com/psf/black"
+Repository = "https://github.com/psf/black"
+Issues = "https://github.com/psf/black/issues"
 
 [tool.hatch.metadata.hooks.fancy-pypi-readme]
 content-type = "text/markdown"
@@ -121,8 +126,8 @@ macos-max-compat = true
 enable-by-default = false
 dependencies = [
   "hatch-mypyc>=0.16.0",
-  "mypy==1.7.1",
-  "click==8.1.3",  # avoid https://github.com/pallets/click/issues/2558
+  "mypy>=1.12",
+  "click>=8.1.7",
 ]
 require-runtime-dependencies = true
 exclude = [
@@ -145,12 +150,14 @@ options = { debug_level = "0" }
 
 [tool.cibuildwheel]
 build-verbosity = 1
+
 # So these are the environments we target:
-# - Python: CPython 3.8+ only
+# - Python: CPython 3.9+ only
 # - Architecture (64-bit only): amd64 / x86_64, universal2, and arm64
 # - OS: Linux (no musl), Windows, and macOS
 build = "cp3*"
 skip = ["*-manylinux_i686", "*-musllinux_*", "*-win32", "pp*"]
+
 # This is the bare minimum needed to run the test suite. Pulling in the full
 # test_requirements.txt would download a bunch of other packages not necessary
 # here and would slow down the testing step a fair bit.
@@ -165,11 +172,9 @@ test-skip = ["*-macosx_arm64", "*-macosx_universal2:arm64"]
 HATCH_BUILD_HOOKS_ENABLE = "1"
 MYPYC_OPT_LEVEL = "3"
 MYPYC_DEBUG_LEVEL = "0"
-# CPython 3.11 wheels aren't available for aiohttp and building a Cython extension
-# from source also doesn't work.
-AIOHTTP_NO_EXTENSIONS = "1"
 
 [tool.cibuildwheel.linux]
+manylinux-x86_64-image = "manylinux_2_28"
 before-build = [
     "yum install -y clang gcc",
 ]
@@ -178,19 +183,10 @@ before-build = [
 HATCH_BUILD_HOOKS_ENABLE = "1"
 MYPYC_OPT_LEVEL = "3"
 MYPYC_DEBUG_LEVEL = "0"
-AIOHTTP_NO_EXTENSIONS = "1"
 
 # Black needs Clang to compile successfully on Linux.
 CC = "clang"
 
-[tool.cibuildwheel.macos]
-build-frontend = { name = "build", args = ["--no-isolation"] }
-# Unfortunately, hatch doesn't respect MACOSX_DEPLOYMENT_TARGET
-before-build = [
-    "python -m pip install 'hatchling==1.18.0' hatch-vcs hatch-fancy-pypi-readme 'hatch-mypyc>=0.16.0' 'mypy==1.7.1' 'click==8.1.3'",
-    """sed -i '' -e "600,700s/'10_16'/os.environ['MACOSX_DEPLOYMENT_TARGET'].replace('.', '_')/" $(python -c 'import hatchling.builders.wheel as h; print(h.__file__)') """,
-]
-
 [tool.isort]
 atomic = true
 profile = "black"
@@ -210,23 +206,7 @@ markers = [
   "incompatible_with_mypyc: run when testing mypyc compiled black"
 ]
 xfail_strict = true
-filterwarnings = [
-    "error",
-    # this is mitigated by a try/catch in https://github.com/psf/black/pull/2974/
-    # this ignore can be removed when support for aiohttp 3.7 is dropped.
-    '''ignore:Decorator `@unittest_run_loop` is no longer needed in aiohttp 3\.8\+:DeprecationWarning''',
-    # this is mitigated by a try/catch in https://github.com/psf/black/pull/3198/
-    # this ignore can be removed when support for aiohttp 3.x is dropped.
-    '''ignore:Middleware decorator is deprecated since 4\.0 and its behaviour is default, you can simply remove this decorator:DeprecationWarning''',
-    # aiohttp is using deprecated cgi modules - Safe to remove when fixed:
-    # https://github.com/aio-libs/aiohttp/issues/6905
-    '''ignore:'cgi' is deprecated and slated for removal in Python 3.13:DeprecationWarning''',
-    # Work around https://github.com/pytest-dev/pytest/issues/10977 for Python 3.12
-    '''ignore:(Attribute s|Attribute n|ast.Str|ast.Bytes|ast.NameConstant|ast.Num) is deprecated and will be removed in Python 3.14:DeprecationWarning''',
-    # Will be fixed with aiohttp 3.9.0
-    # https://github.com/aio-libs/aiohttp/pull/7302
-    "ignore:datetime.*utcfromtimestamp\\(\\) is deprecated and scheduled for removal:DeprecationWarning",
-]
+filterwarnings = ["error"]
 [tool.coverage.report]
 omit = [
   "src/blib2to3/*",
@@ -242,9 +222,11 @@ branch = true
 # Specify the target platform details in config, so your developers are
 # free to run mypy on Windows, Linux, or macOS and get consistent
 # results.
-python_version = "3.8"
+python_version = "3.9"
 mypy_path = "src"
 strict = true
+strict_bytes = true
+local_partial_types = true
 # Unreachable blocks have been an issue when compiling mypyc, let's try to avoid 'em in the first place.
 warn_unreachable = true
 implicit_reexport = true

scripts/diff_shades_gha_helper.py

@@ -24,17 +24,12 @@
 from base64 import b64encode
 from io import BytesIO
 from pathlib import Path
-from typing import Any
+from typing import Any, Final, Literal
 
 import click
 import urllib3
 from packaging.version import Version
 
-if sys.version_info >= (3, 8):
-    from typing import Final, Literal
-else:
-    from typing_extensions import Final, Literal
-
 COMMENT_FILE: Final = ".pr-comment.json"
 DIFF_STEP_NAME: Final = "Generate HTML diff report"
 DOCS_URL: Final = (

scripts/fuzz.py

@@ -5,14 +5,11 @@
 a coverage-guided fuzzer I'm working on.
 """
 
-import re
-
 import hypothesmith
 from hypothesis import HealthCheck, given, settings
 from hypothesis import strategies as st
 
 import black
-from blib2to3.pgen2.tokenize import TokenError
 
 
 # This test uses the Hypothesis and Hypothesmith libraries to generate random
@@ -45,23 +42,7 @@ def test_idempotent_any_syntatically_valid_python(
     compile(src_contents, "<string>", "exec")  # else the bug is in hypothesmith
 
     # Then format the code...
-    try:
-        dst_contents = black.format_str(src_contents, mode=mode)
-    except black.InvalidInput:
-        # This is a bug - if it's valid Python code, as above, Black should be
-        # able to cope with it.  See issues #970, #1012
-        # TODO: remove this try-except block when issues are resolved.
-        return
-    except TokenError as e:
-        if (  # Special-case logic for backslashes followed by newlines or end-of-input
-            e.args[0] == "EOF in multi-line statement"
-            and re.search(r"\\($|\r?\n)", src_contents) is not None
-        ):
-            # This is a bug - if it's valid Python code, as above, Black should be
-            # able to cope with it.  See issue #1012.
-            # TODO: remove this block when the issue is resolved.
-            return
-        raise
+    dst_contents = black.format_str(src_contents, mode=mode)
 
     # And check that we got equivalent and stable output.
     black.assert_equivalent(src_contents, dst_contents)
@@ -80,7 +61,7 @@ def test_idempotent_any_syntatically_valid_python(
     try:
         import sys
 
-        import atheris  # type: ignore[import-not-found]
+        import atheris
     except ImportError:
         pass
     else:

scripts/generate_schema.py

@@ -0,0 +1,74 @@
+import json
+from typing import IO, Any
+
+import click
+
+import black
+
+
+def generate_schema_from_click(
+    cmd: click.Command,
+) -> dict[str, Any]:
+    result: dict[str, dict[str, Any]] = {}
+    for param in cmd.params:
+        if not isinstance(param, click.Option) or param.is_eager:
+            continue
+
+        assert param.name
+        name = param.name.replace("_", "-")
+
+        result[name] = {}
+
+        match param.type:
+            case click.types.IntParamType():
+                result[name]["type"] = "integer"
+            case click.types.StringParamType() | click.types.Path():
+                result[name]["type"] = "string"
+            case click.types.Choice(choices=choices):
+                result[name]["enum"] = choices
+            case click.types.BoolParamType():
+                result[name]["type"] = "boolean"
+            case _:
+                msg = f"{param.type!r} not a known type for {param}"
+                raise TypeError(msg)
+
+        if param.multiple:
+            result[name] = {"type": "array", "items": result[name]}
+
+        result[name]["description"] = param.help
+
+        if param.default is not None and not param.multiple:
+            result[name]["default"] = param.default
+
+    return result
+
+
+@click.command(context_settings={"help_option_names": ["-h", "--help"]})
+@click.option("--schemastore", is_flag=True, help="SchemaStore format")
+@click.option("--outfile", type=click.File(mode="w"), help="Write to file")
+def main(schemastore: bool, outfile: IO[str]) -> None:
+    properties = generate_schema_from_click(black.main)
+    del properties["line-ranges"]
+
+    schema: dict[str, Any] = {
+        "$schema": "http://json-schema.org/draft-07/schema#",
+        "$id": (
+            "https://github.com/psf/black/blob/main/src/black/resources/black.schema.json"
+        ),
+        "$comment": "tool.black table in pyproject.toml",
+        "type": "object",
+        "additionalProperties": False,
+        "properties": properties,
+    }
+
+    if schemastore:
+        schema["$id"] = "https://json.schemastore.org/partial-black.json"
+        # The precise list of unstable features may change frequently, so don't
+        # bother putting it in SchemaStore
+        schema["properties"]["enable-unstable-feature"]["items"] = {"type": "string"}
+
+    print(json.dumps(schema, indent=2), file=outfile)
+
+
+if __name__ == "__main__":
+    main()

scripts/make_width_table.py

@@ -17,13 +17,13 @@
 """
 
 import sys
+from collections.abc import Iterable
 from os.path import basename, dirname, join
-from typing import Iterable, Tuple
 
 import wcwidth  # type: ignore[import-not-found]
 
 
-def make_width_table() -> Iterable[Tuple[int, int, int]]:
+def make_width_table() -> Iterable[tuple[int, int, int]]:
     start_codepoint = -1
     end_codepoint = -1
     range_width = -2
@@ -53,9 +53,9 @@ def main() -> None:
         f.write(f"""# Generated by {basename(__file__)}
 # wcwidth {wcwidth.__version__}
 # Unicode {wcwidth.list_versions()[-1]}
-from typing import Final, List, Tuple
+from typing import Final
 
-WIDTH_TABLE: Final[List[Tuple[int, int, int]]] = [
+WIDTH_TABLE: Final[list[tuple[int, int, int]]] = [
 """)
         for triple in make_width_table():
             f.write(f"    {triple!r},\n")

scripts/migrate-black.py

@@ -9,7 +9,7 @@
 
 
 def git(*args: str) -> str:
-    return check_output(["git"] + list(args)).decode("utf8").strip()
+    return check_output(["git", *args]).decode("utf8").strip()
 
 
 def blackify(base_branch: str, black_command: str, logger: logging.Logger) -> int:
@@ -26,19 +26,19 @@ def blackify(base_branch: str, black_command: str, logger: logging.Logger) -> in
     merge_base = git("merge-base", "HEAD", base_branch)
     if not merge_base:
         logger.error(
-            "Could not find a common commit for current head and %s" % base_branch
+            f"Could not find a common commit for current head and {base_branch}"
         )
         return 1
 
     commits = git(
-        "log", "--reverse", "--pretty=format:%H", "%s~1..HEAD" % merge_base
+        "log", "--reverse", "--pretty=format:%H", f"{merge_base}~1..HEAD"
     ).split()
     for commit in commits:
-        git("checkout", commit, "-b%s-black" % commit)
+        git("checkout", commit, f"-b{commit}-black")
         check_output(black_command, shell=True)
         git("commit", "-aqm", "blackify")
 
-    git("checkout", base_branch, "-b%s-black" % current_branch)
+    git("checkout", base_branch, f"-b{current_branch}-black")
 
     for last_commit, commit in zip(commits, commits[1:]):
         allow_empty = (
@@ -51,7 +51,7 @@ def blackify(base_branch: str, black_command: str, logger: logging.Logger) -> in
                 "diff",
                 "--binary",
                 "--find-copies",
-                "%s-black..%s-black" % (last_commit, commit),
+                f"{last_commit}-black..{commit}-black",
             ],
             stdout=PIPE,
         )
@@ -77,7 +77,7 @@ def blackify(base_branch: str, black_command: str, logger: logging.Logger) -> in
         git("commit", "--allow-empty", "-aqC", commit)
 
     for commit in commits:
-        git("branch", "-qD", "%s-black" % commit)
+        git("branch", "-qD", f"{commit}-black")
 
     return 0
 

scripts/release.py

@@ -11,8 +11,7 @@
 import sys
 from datetime import datetime
 from pathlib import Path
-from subprocess import PIPE, run
-from typing import List
+from subprocess import run
 
 LOG = logging.getLogger(__name__)
 NEW_VERSION_CHANGELOG_TEMPLATE = """\
@@ -70,9 +69,9 @@ class NoGitTagsError(Exception): ...  # noqa: E701,E761
 
 # TODO: Do better with alpha + beta releases
 # Maybe we vendor packaging library
-def get_git_tags(versions_only: bool = True) -> List[str]:
+def get_git_tags(versions_only: bool = True) -> list[str]:
     """Pull out all tags or calvers only"""
-    cp = run(["git", "tag"], stdout=PIPE, stderr=PIPE, check=True, encoding="utf8")
+    cp = run(["git", "tag"], capture_output=True, check=True, encoding="utf8")
     if not cp.stdout:
         LOG.error(f"Returned no git tags stdout: {cp.stderr}")
         raise NoGitTagsError
@@ -169,7 +168,9 @@ def get_next_version(self) -> str:
         calver_parts = base_calver.split(".")
         base_calver = f"{calver_parts[0]}.{int(calver_parts[1])}"  # Remove leading 0
         git_tags = get_git_tags()
-        same_month_releases = [t for t in git_tags if t.startswith(base_calver)]
+        same_month_releases = [
+            t for t in git_tags if t.startswith(base_calver) and "a" not in t
+        ]
         if len(same_month_releases) < 1:
             return f"{base_calver}.0"
         same_month_version = same_month_releases[-1].split(".", 2)[-1]

src/black/__init__.py

@@ -5,28 +5,22 @@
 import sys
 import tokenize
 import traceback
+from collections.abc import (
+    Collection,
+    Generator,
+    Iterator,
+    MutableMapping,
+    Sequence,
+    Sized,
+)
 from contextlib import contextmanager
 from dataclasses import replace
 from datetime import datetime, timezone
 from enum import Enum
 from json.decoder import JSONDecodeError
 from pathlib import Path
-from typing import (
-    Any,
-    Collection,
-    Dict,
-    Generator,
-    Iterator,
-    List,
-    MutableMapping,
-    Optional,
-    Pattern,
-    Sequence,
-    Set,
-    Sized,
-    Tuple,
-    Union,
-)
+from re import Pattern
+from typing import Any, Optional, Union
 
 import click
 from click.core import ParameterSource
@@ -44,43 +38,47 @@
     STDIN_PLACEHOLDER,
 )
 from black.files import (
+    best_effort_relative_path,
     find_project_root,
     find_pyproject_toml,
     find_user_pyproject_toml,
     gen_python_files,
     get_gitignore,
-    normalize_path_maybe_ignore,
     parse_pyproject_toml,
     path_is_excluded,
+    resolves_outside_root_or_cannot_stat,
     wrap_stream_for_windows,
 )
 from black.handle_ipynb_magics import (
     PYTHON_CELL_MAGICS,
-    TRANSFORMED_MAGICS,
     jupyter_dependencies_are_installed,
     mask_cell,
     put_trailing_semicolon_back,
     remove_trailing_semicolon,
     unmask_cell,
+    validate_cell,
 )
 from black.linegen import LN, LineGenerator, transform_line
 from black.lines import EmptyLineTracker, LinesBlock
 from black.mode import FUTURE_FLAG_TO_FEATURE, VERSION_TO_FEATURES, Feature
 from black.mode import Mode as Mode  # re-exported
-from black.mode import TargetVersion, supports_feature
-from black.nodes import (
-    STARS,
-    is_number_token,
-    is_simple_decorator_expression,
-    is_string_token,
-    syms,
-)
+from black.mode import Preview, TargetVersion, supports_feature
+from black.nodes import STARS, is_number_token, is_simple_decorator_expression, syms
 from black.output import color_diff, diff, dump_to_file, err, ipynb_diff, out
-from black.parsing import InvalidInput  # noqa F401
-from black.parsing import lib2to3_parse, parse_ast, stringify_ast
-from black.ranges import adjusted_lines, convert_unchanged_lines, parse_line_ranges
+from black.parsing import (  # noqa F401
+    ASTSafetyError,
+    InvalidInput,
+    lib2to3_parse,
+    parse_ast,
+    stringify_ast,
+)
+from black.ranges import (
+    adjusted_lines,
+    convert_unchanged_lines,
+    parse_line_ranges,
+    sanitized_lines,
+)
 from black.report import Changed, NothingChanged, Report
-from black.trans import iter_fexpr_spans
 from blib2to3.pgen2 import token
 from blib2to3.pytree import Leaf, Node
 
@@ -141,6 +139,7 @@ def read_pyproject_toml(
     if not config:
         return None
     else:
+        spellcheck_pyproject_toml_keys(ctx, list(config), value)
         # Sanitize the values to be Click friendly. For more information please see:
         # https://github.com/psf/black/issues/1458
         # https://github.com/pallets/click/issues/1567
@@ -171,7 +170,7 @@ def read_pyproject_toml(
             "line-ranges", "Cannot use line-ranges in the pyproject.toml file."
         )
 
-    default_map: Dict[str, Any] = {}
+    default_map: dict[str, Any] = {}
     if ctx.default_map:
         default_map.update(ctx.default_map)
     default_map.update(config)
@@ -180,9 +179,25 @@ def read_pyproject_toml(
     return value
 
 
+def spellcheck_pyproject_toml_keys(
+    ctx: click.Context, config_keys: list[str], config_file_path: str
+) -> None:
+    invalid_keys: list[str] = []
+    available_config_options = {param.name for param in ctx.command.params}
+    for key in config_keys:
+        if key not in available_config_options:
+            invalid_keys.append(key)
+    if invalid_keys:
+        keys_str = ", ".join(map(repr, invalid_keys))
+        out(
+            f"Invalid config keys detected: {keys_str} (in {config_file_path})",
+            fg="red",
+        )
+
+
 def target_version_option_callback(
-    c: click.Context, p: Union[click.Option, click.Parameter], v: Tuple[str, ...]
-) -> List[TargetVersion]:
+    c: click.Context, p: Union[click.Option, click.Parameter], v: tuple[str, ...]
+) -> list[TargetVersion]:
     """Compute the target versions from a --target-version flag.
 
     This is its own function because mypy couldn't infer the type correctly
@@ -191,6 +206,13 @@ def target_version_option_callback(
     return [TargetVersion[val.upper()] for val in v]
 
 
+def enable_unstable_feature_callback(
+    c: click.Context, p: Union[click.Option, click.Parameter], v: tuple[str, ...]
+) -> list[Preview]:
+    """Compute the features from an --enable-unstable-feature flag."""
+    return [Preview[val] for val in v]
+
+
 def re_compile_maybe_verbose(regex: str) -> Pattern[str]:
     """Compile a regular expression string in `regex`.
 
@@ -254,7 +276,7 @@ def validate_regex(
     is_flag=True,
     help=(
         "Format all input files like Jupyter Notebooks regardless of file extension."
-        "This is useful when piping source on standard input."
+        " This is useful when piping source on standard input."
     ),
 )
 @click.option(
@@ -285,12 +307,6 @@ def validate_regex(
     is_flag=True,
     help="Don't use trailing commas as a reason to split lines.",
 )
-@click.option(
-    "--experimental-string-processing",
-    is_flag=True,
-    hidden=True,
-    help="(DEPRECATED and now included in --preview) Normalize string literals.",
-)
 @click.option(
     "--preview",
     is_flag=True,
@@ -299,6 +315,26 @@ def validate_regex(
         " functionality in the next major release."
     ),
 )
+@click.option(
+    "--unstable",
+    is_flag=True,
+    help=(
+        "Enable potentially disruptive style changes that have known bugs or are not"
+        " currently expected to make it into the stable style Black's next major"
+        " release. Implies --preview."
+    ),
+)
+@click.option(
+    "--enable-unstable-feature",
+    type=click.Choice([v.name for v in Preview]),
+    callback=enable_unstable_feature_callback,
+    multiple=True,
+    help=(
+        "Enable specific features included in the `--unstable` style. Requires"
+        " `--preview`. No compatibility guarantees are provided on the behavior"
+        " or existence of any unstable features."
+    ),
+)
 @click.option(
     "--check",
     is_flag=True,
@@ -477,7 +513,7 @@ def main(  # noqa: C901
     ctx: click.Context,
     code: Optional[str],
     line_length: int,
-    target_version: List[TargetVersion],
+    target_version: list[TargetVersion],
     check: bool,
     diff: bool,
     line_ranges: Sequence[str],
@@ -489,8 +525,9 @@ def main(  # noqa: C901
     skip_source_first_line: bool,
     skip_string_normalization: bool,
     skip_magic_trailing_comma: bool,
-    experimental_string_processing: bool,
     preview: bool,
+    unstable: bool,
+    enable_unstable_feature: list[Preview],
     quiet: bool,
     verbose: bool,
     required_version: Optional[str],
@@ -500,12 +537,21 @@ def main(  # noqa: C901
     force_exclude: Optional[Pattern[str]],
     stdin_filename: Optional[str],
     workers: Optional[int],
-    src: Tuple[str, ...],
+    src: tuple[str, ...],
     config: Optional[str],
 ) -> None:
     """The uncompromising code formatter."""
     ctx.ensure_object(dict)
 
+    assert sys.version_info >= (3, 9), "Black requires Python 3.9+"
+    if sys.version_info[:3] == (3, 12, 5):
+        out(
+            "Python 3.12.5 has a memory safety issue that can cause Black's "
+            "AST safety checks to fail. "
+            "Please upgrade to Python 3.12.6 or downgrade to Python 3.12.4"
+        )
+        ctx.exit(1)
+
     if src and code is not None:
         out(
             main.get_usage(ctx)
@@ -516,6 +562,14 @@ def main(  # noqa: C901
         out(main.get_usage(ctx) + "\n\nOne of 'SRC' or 'code' is required.")
         ctx.exit(1)
 
+    # It doesn't do anything if --unstable is also passed, so just allow it.
+    if enable_unstable_feature and not (preview or unstable):
+        out(
+            main.get_usage(ctx)
+            + "\n\n'--enable-unstable-feature' requires '--preview'."
+        )
+        ctx.exit(1)
+
     root, method = (
         find_project_root(src, stdin_filename) if code is None else (None, None)
     )
@@ -577,12 +631,13 @@ def main(  # noqa: C901
         skip_source_first_line=skip_source_first_line,
         string_normalization=not skip_string_normalization,
         magic_trailing_comma=not skip_magic_trailing_comma,
-        experimental_string_processing=experimental_string_processing,
         preview=preview,
+        unstable=unstable,
         python_cell_magics=set(python_cell_magics),
+        enabled_features=set(enable_unstable_feature),
     )
 
-    lines: List[Tuple[int, int]] = []
+    lines: list[tuple[int, int]] = []
     if line_ranges:
         if ipynb:
             err("Cannot use --line-ranges with ipynb files.")
@@ -672,7 +727,7 @@ def main(  # noqa: C901
 def get_sources(
     *,
     root: Path,
-    src: Tuple[str, ...],
+    src: tuple[str, ...],
     quiet: bool,
     verbose: bool,
     include: Pattern[str],
@@ -681,18 +736,25 @@ def get_sources(
     force_exclude: Optional[Pattern[str]],
     report: "Report",
     stdin_filename: Optional[str],
-) -> Set[Path]:
+) -> set[Path]:
     """Compute the set of files to be formatted."""
-    sources: Set[Path] = set()
+    sources: set[Path] = set()
 
+    assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
     using_default_exclude = exclude is None
     exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES) if exclude is None else exclude
-    gitignore: Optional[Dict[Path, PathSpec]] = None
+    gitignore: Optional[dict[Path, PathSpec]] = None
     root_gitignore = get_gitignore(root)
 
     for s in src:
         if s == "-" and stdin_filename:
             path = Path(stdin_filename)
+            if path_is_excluded(stdin_filename, force_exclude):
+                report.path_ignored(
+                    path,
+                    "--stdin-filename matches the --force-exclude regular expression",
+                )
+                continue
             is_stdin = True
         else:
             path = Path(s)
@@ -700,8 +762,12 @@ def get_sources(
 
         # Compare the logic here to the logic in `gen_python_files`.
         if is_stdin or path.is_file():
-            root_relative_path = path.absolute().relative_to(root).as_posix()
+            if resolves_outside_root_or_cannot_stat(path, root, report):
+                if verbose:
+                    out(f'Skipping invalid source: "{path}"', fg="red")
+                continue
 
+            root_relative_path = best_effort_relative_path(path, root).as_posix()
             root_relative_path = "/" + root_relative_path
 
             # Hard-exclude any files that matches the `--force-exclude` regex.
@@ -711,14 +777,6 @@ def get_sources(
                 )
                 continue
 
-            normalized_path: Optional[str] = normalize_path_maybe_ignore(
-                path, root, report
-            )
-            if normalized_path is None:
-                if verbose:
-                    out(f'Skipping invalid source: "{normalized_path}"', fg="red")
-                continue
-
             if is_stdin:
                 path = Path(f"{STDIN_PLACEHOLDER}{str(path)}")
 
@@ -728,7 +786,7 @@ def get_sources(
                 continue
 
             if verbose:
-                out(f'Found input source: "{normalized_path}"', fg="blue")
+                out(f'Found input source: "{path}"', fg="blue")
             sources.add(path)
         elif path.is_dir():
             path = root / (path.resolve().relative_to(root))
@@ -783,7 +841,7 @@ def reformat_code(
     mode: Mode,
     report: Report,
     *,
-    lines: Collection[Tuple[int, int]] = (),
+    lines: Collection[tuple[int, int]] = (),
 ) -> None:
     """
     Reformat and print out `content` without spawning child processes.
@@ -816,7 +874,7 @@ def reformat_one(
     mode: Mode,
     report: "Report",
     *,
-    lines: Collection[Tuple[int, int]] = (),
+    lines: Collection[tuple[int, int]] = (),
 ) -> None:
     """Reformat a single file under `src` without spawning child processes.
 
@@ -872,7 +930,7 @@ def format_file_in_place(
     write_back: WriteBack = WriteBack.NO,
     lock: Any = None,  # multiprocessing.Manager().Lock() is some crazy proxy
     *,
-    lines: Collection[Tuple[int, int]] = (),
+    lines: Collection[tuple[int, int]] = (),
 ) -> bool:
     """Format file under `src` path. Return True if changed.
 
@@ -939,7 +997,7 @@ def format_stdin_to_stdout(
     content: Optional[str] = None,
     write_back: WriteBack = WriteBack.NO,
     mode: Mode,
-    lines: Collection[Tuple[int, int]] = (),
+    lines: Collection[tuple[int, int]] = (),
 ) -> bool:
     """Format file on stdin. Return True if changed.
 
@@ -990,7 +1048,7 @@ def check_stability_and_equivalence(
     dst_contents: str,
     *,
     mode: Mode,
-    lines: Collection[Tuple[int, int]] = (),
+    lines: Collection[tuple[int, int]] = (),
 ) -> None:
     """Perform stability and equivalence checks.
 
@@ -1007,7 +1065,7 @@ def format_file_contents(
     *,
     fast: bool,
     mode: Mode,
-    lines: Collection[Tuple[int, int]] = (),
+    lines: Collection[tuple[int, int]] = (),
 ) -> FileContent:
     """Reformat contents of a file and return new contents.
 
@@ -1030,32 +1088,6 @@ def format_file_contents(
     return dst_contents
 
 
-def validate_cell(src: str, mode: Mode) -> None:
-    """Check that cell does not already contain TransformerManager transformations,
-    or non-Python cell magics, which might cause tokenizer_rt to break because of
-    indentations.
-
-    If a cell contains ``!ls``, then it'll be transformed to
-    ``get_ipython().system('ls')``. However, if the cell originally contained
-    ``get_ipython().system('ls')``, then it would get transformed in the same way:
-
-        >>> TransformerManager().transform_cell("get_ipython().system('ls')")
-        "get_ipython().system('ls')\n"
-        >>> TransformerManager().transform_cell("!ls")
-        "get_ipython().system('ls')\n"
-
-    Due to the impossibility of safely roundtripping in such situations, cells
-    containing transformed magics will be ignored.
-    """
-    if any(transformed_magic in src for transformed_magic in TRANSFORMED_MAGICS):
-        raise NothingChanged
-    if (
-        src[:2] == "%%"
-        and src.split()[0][2:] not in PYTHON_CELL_MAGICS | mode.python_cell_magics
-    ):
-        raise NothingChanged
-
-
 def format_cell(src: str, *, fast: bool, mode: Mode) -> str:
     """Format code in given cell of Jupyter notebook.
 
@@ -1138,7 +1170,7 @@ def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileCon
 
 
 def format_str(
-    src_contents: str, *, mode: Mode, lines: Collection[Tuple[int, int]] = ()
+    src_contents: str, *, mode: Mode, lines: Collection[tuple[int, int]] = ()
 ) -> str:
     """Reformat a string and return new contents.
 
@@ -1169,6 +1201,10 @@ def f(
         hey
 
     """
+    if lines:
+        lines = sanitized_lines(lines, src_contents)
+        if not lines:
+            return src_contents  # Nothing to format
     dst_contents = _format_str_once(src_contents, mode=mode, lines=lines)
     # Forced second pass to work around optional trailing commas (becoming
     # forced trailing commas on pass 2) interacting differently with optional
@@ -1181,10 +1217,10 @@ def f(
 
 
 def _format_str_once(
-    src_contents: str, *, mode: Mode, lines: Collection[Tuple[int, int]] = ()
+    src_contents: str, *, mode: Mode, lines: Collection[tuple[int, int]] = ()
 ) -> str:
     src_node = lib2to3_parse(src_contents.lstrip(), mode.target_versions)
-    dst_blocks: List[LinesBlock] = []
+    dst_blocks: list[LinesBlock] = []
     if mode.target_versions:
         versions = mode.target_versions
     else:
@@ -1205,7 +1241,10 @@ def _format_str_once(
     elt = EmptyLineTracker(mode=mode)
     split_line_features = {
         feature
-        for feature in {Feature.TRAILING_COMMA_IN_CALL, Feature.TRAILING_COMMA_IN_DEF}
+        for feature in {
+            Feature.TRAILING_COMMA_IN_CALL,
+            Feature.TRAILING_COMMA_IN_DEF,
+        }
         if supports_feature(versions, feature)
     }
     block: Optional[LinesBlock] = None
@@ -1231,7 +1270,7 @@ def _format_str_once(
     return "".join(dst_contents)
 
 
-def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
+def decode_bytes(src: bytes) -> tuple[FileContent, Encoding, NewLine]:
     """Return a tuple of (decoded_contents, encoding, newline).
 
     `newline` is either CRLF or LF but `decoded_contents` is decoded with
@@ -1249,8 +1288,8 @@ def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
 
 
 def get_features_used(  # noqa: C901
-    node: Node, *, future_imports: Optional[Set[str]] = None
-) -> Set[Feature]:
+    node: Node, *, future_imports: Optional[set[str]] = None
+) -> set[Feature]:
     """Return a set of (relatively) new Python features used in this file.
 
     Currently looking for:
@@ -1268,7 +1307,7 @@ def get_features_used(  # noqa: C901
     - except* clause;
     - variadic generics;
     """
-    features: Set[Feature] = set()
+    features: set[Feature] = set()
     if future_imports:
         features |= {
             FUTURE_FLAG_TO_FEATURE[future_import]
@@ -1277,15 +1316,14 @@ def get_features_used(  # noqa: C901
         }
 
     for n in node.pre_order():
-        if is_string_token(n):
-            value_head = n.value[:2]
-            if value_head in {'f"', 'F"', "f'", "F'", "rf", "fr", "RF", "FR"}:
-                features.add(Feature.F_STRINGS)
-                if Feature.DEBUG_F_STRINGS not in features:
-                    for span_beg, span_end in iter_fexpr_spans(n.value):
-                        if n.value[span_beg : span_end - 1].rstrip().endswith("="):
-                            features.add(Feature.DEBUG_F_STRINGS)
-                            break
+        if n.type == token.FSTRING_START:
+            features.add(Feature.F_STRINGS)
+        elif (
+            n.type == token.RBRACE
+            and n.parent is not None
+            and any(child.type == token.EQUAL for child in n.parent.children)
+        ):
+            features.add(Feature.DEBUG_F_STRINGS)
 
         elif is_number_token(n):
             if "_" in n.value:
@@ -1381,6 +1419,12 @@ def get_features_used(  # noqa: C901
         elif n.type in (syms.type_stmt, syms.typeparams):
             features.add(Feature.TYPE_PARAMS)
 
+        elif (
+            n.type in (syms.typevartuple, syms.paramspec, syms.typevar)
+            and n.children[-2].type == token.EQUAL
+        ):
+            features.add(Feature.TYPE_PARAM_DEFAULTS)
+
     return features
 
 
@@ -1401,8 +1445,8 @@ def _contains_asexpr(node: Union[Node, Leaf]) -> bool:
 
 
 def detect_target_versions(
-    node: Node, *, future_imports: Optional[Set[str]] = None
-) -> Set[TargetVersion]:
+    node: Node, *, future_imports: Optional[set[str]] = None
+) -> set[TargetVersion]:
     """Detect the version to target based on the nodes used."""
     features = get_features_used(node, future_imports=future_imports)
     return {
@@ -1410,11 +1454,11 @@ def detect_target_versions(
     }
 
 
-def get_future_imports(node: Node) -> Set[str]:
+def get_future_imports(node: Node) -> set[str]:
     """Return a set of __future__ imports in the file."""
-    imports: Set[str] = set()
+    imports: set[str] = set()
 
-    def get_imports_from_children(children: List[LN]) -> Generator[str, None, None]:
+    def get_imports_from_children(children: list[LN]) -> Generator[str, None, None]:
         for child in children:
             if isinstance(child, Leaf):
                 if child.type == token.NAME:
@@ -1460,12 +1504,19 @@ def get_imports_from_children(children: List[LN]) -> Generator[str, None, None]:
     return imports
 
 
+def _black_info() -> str:
+    return (
+        f"Black {__version__} on "
+        f"Python ({platform.python_implementation()}) {platform.python_version()}"
+    )
+
+
 def assert_equivalent(src: str, dst: str) -> None:
     """Raise AssertionError if `src` and `dst` aren't equivalent."""
     try:
         src_ast = parse_ast(src)
     except Exception as exc:
-        raise AssertionError(
+        raise ASTSafetyError(
             "cannot use --safe with this file; failed to parse source file AST: "
             f"{exc}\n"
             "This could be caused by running Black with an older Python version "
@@ -1476,8 +1527,8 @@ def assert_equivalent(src: str, dst: str) -> None:
         dst_ast = parse_ast(dst)
     except Exception as exc:
         log = dump_to_file("".join(traceback.format_tb(exc.__traceback__)), dst)
-        raise AssertionError(
-            f"INTERNAL ERROR: Black produced invalid code: {exc}. "
+        raise ASTSafetyError(
+            f"INTERNAL ERROR: {_black_info()} produced invalid code: {exc}. "
             "Please report a bug on https://github.com/psf/black/issues.  "
             f"This invalid output might be helpful: {log}"
         ) from None
@@ -1486,15 +1537,15 @@ def assert_equivalent(src: str, dst: str) -> None:
     dst_ast_str = "\n".join(stringify_ast(dst_ast))
     if src_ast_str != dst_ast_str:
         log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst"))
-        raise AssertionError(
-            "INTERNAL ERROR: Black produced code that is not equivalent to the"
-            " source.  Please report a bug on "
-            f"https://github.com/psf/black/issues.  This diff might be helpful: {log}"
+        raise ASTSafetyError(
+            f"INTERNAL ERROR: {_black_info()} produced code that is not equivalent to"
+            " the source.  Please report a bug on https://github.com/psf/black/issues."
+            f"  This diff might be helpful: {log}"
         ) from None
 
 
 def assert_stable(
-    src: str, dst: str, mode: Mode, *, lines: Collection[Tuple[int, int]] = ()
+    src: str, dst: str, mode: Mode, *, lines: Collection[tuple[int, int]] = ()
 ) -> None:
     """Raise AssertionError if `dst` reformats differently the second time."""
     if lines:
@@ -1515,9 +1566,9 @@ def assert_stable(
             diff(dst, newdst, "first pass", "second pass"),
         )
         raise AssertionError(
-            "INTERNAL ERROR: Black produced different code on the second pass of the"
-            " formatter.  Please report a bug on https://github.com/psf/black/issues."
-            f"  This diff might be helpful: {log}"
+            f"INTERNAL ERROR: {_black_info()} produced different code on the second"
+            " pass of the formatter.  Please report a bug on"
+            f" https://github.com/psf/black/issues.  This diff might be helpful: {log}"
         ) from None
 
 

src/black/_width_table.py

@@ -1,9 +1,9 @@
 # Generated by make_width_table.py
 # wcwidth 0.2.6
 # Unicode 15.0.0
-from typing import Final, List, Tuple
+from typing import Final
 
-WIDTH_TABLE: Final[List[Tuple[int, int, int]]] = [
+WIDTH_TABLE: Final[list[tuple[int, int, int]]] = [
     (0, 0, 0),
     (1, 31, -1),
     (127, 159, -1),

src/black/brackets.py

@@ -1,7 +1,8 @@
 """Builds on top of nodes.py to track brackets."""
 
+from collections.abc import Iterable, Sequence
 from dataclasses import dataclass, field
-from typing import Dict, Final, Iterable, List, Optional, Sequence, Set, Tuple, Union
+from typing import Final, Optional, Union
 
 from black.nodes import (
     BRACKET,
@@ -60,12 +61,12 @@ class BracketTracker:
     """Keeps track of brackets on a line."""
 
     depth: int = 0
-    bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = field(default_factory=dict)
-    delimiters: Dict[LeafID, Priority] = field(default_factory=dict)
+    bracket_match: dict[tuple[Depth, NodeType], Leaf] = field(default_factory=dict)
+    delimiters: dict[LeafID, Priority] = field(default_factory=dict)
     previous: Optional[Leaf] = None
-    _for_loop_depths: List[int] = field(default_factory=list)
-    _lambda_argument_depths: List[int] = field(default_factory=list)
-    invisible: List[Leaf] = field(default_factory=list)
+    _for_loop_depths: list[int] = field(default_factory=list)
+    _lambda_argument_depths: list[int] = field(default_factory=list)
+    invisible: list[Leaf] = field(default_factory=list)
 
     def mark(self, leaf: Leaf) -> None:
         """Mark `leaf` with bracket-related metadata. Keep track of delimiters.
@@ -115,7 +116,7 @@ def mark(self, leaf: Leaf) -> None:
             if delim and self.previous is not None:
                 self.delimiters[id(self.previous)] = delim
             else:
-                delim = is_split_after_delimiter(leaf, self.previous)
+                delim = is_split_after_delimiter(leaf)
                 if delim:
                     self.delimiters[id(leaf)] = delim
         if leaf.type in OPENING_BRACKETS:
@@ -215,7 +216,7 @@ def get_open_lsqb(self) -> Optional[Leaf]:
         return self.bracket_match.get((self.depth - 1, token.RSQB))
 
 
-def is_split_after_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
+def is_split_after_delimiter(leaf: Leaf) -> Priority:
     """Return the priority of the `leaf` delimiter, given a line break after it.
 
     The delimiter priorities returned here are from those delimiters that would
@@ -353,7 +354,7 @@ def max_delimiter_priority_in_atom(node: LN) -> Priority:
         return 0
 
 
-def get_leaves_inside_matching_brackets(leaves: Sequence[Leaf]) -> Set[LeafID]:
+def get_leaves_inside_matching_brackets(leaves: Sequence[Leaf]) -> set[LeafID]:
     """Return leaves that are inside matching brackets.
 
     The input `leaves` can have non-matching brackets at the head or tail parts.

src/black/cache.py

@@ -5,14 +5,16 @@
 import pickle
 import sys
 import tempfile
+from collections.abc import Iterable
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Dict, Iterable, NamedTuple, Set, Tuple
+from typing import NamedTuple
 
 from platformdirs import user_cache_dir
 
 from _black_version import version as __version__
 from black.mode import Mode
+from black.output import err
 
 if sys.version_info >= (3, 11):
     from typing import Self
@@ -54,22 +56,28 @@ def get_cache_file(mode: Mode) -> Path:
 class Cache:
     mode: Mode
     cache_file: Path
-    file_data: Dict[str, FileData] = field(default_factory=dict)
+    file_data: dict[str, FileData] = field(default_factory=dict)
 
     @classmethod
     def read(cls, mode: Mode) -> Self:
-        """Read the cache if it exists and is well formed.
+        """Read the cache if it exists and is well-formed.
 
-        If it is not well formed, the call to write later should
+        If it is not well-formed, the call to write later should
         resolve the issue.
         """
         cache_file = get_cache_file(mode)
-        if not cache_file.exists():
+        try:
+            exists = cache_file.exists()
+        except OSError as e:
+            # Likely file too long; see #4172 and #4174
+            err(f"Unable to read cache file {cache_file} due to {e}")
+            return cls(mode, cache_file)
+        if not exists:
             return cls(mode, cache_file)
 
         with cache_file.open("rb") as fobj:
             try:
-                data: Dict[str, Tuple[float, int, str]] = pickle.load(fobj)
+                data: dict[str, tuple[float, int, str]] = pickle.load(fobj)
                 file_data = {k: FileData(*v) for k, v in data.items()}
             except (pickle.UnpicklingError, ValueError, IndexError):
                 return cls(mode, cache_file)
@@ -101,20 +109,20 @@ def is_changed(self, source: Path) -> bool:
         st = res_src.stat()
         if st.st_size != old.st_size:
             return True
-        if int(st.st_mtime) != int(old.st_mtime):
+        if st.st_mtime != old.st_mtime:
             new_hash = Cache.hash_digest(res_src)
             if new_hash != old.hash:
                 return True
         return False
 
-    def filtered_cached(self, sources: Iterable[Path]) -> Tuple[Set[Path], Set[Path]]:
+    def filtered_cached(self, sources: Iterable[Path]) -> tuple[set[Path], set[Path]]:
         """Split an iterable of paths in `sources` into two sets.
 
         The first contains paths of files that modified on disk or are not in the
         cache. The other contains paths to non-modified files.
         """
-        changed: Set[Path] = set()
-        done: Set[Path] = set()
+        changed: set[Path] = set()
+        done: set[Path] = set()
         for src in sources:
             if self.is_changed(src):
                 changed.add(src)
@@ -132,9 +140,8 @@ def write(self, sources: Iterable[Path]) -> None:
             with tempfile.NamedTemporaryFile(
                 dir=str(self.cache_file.parent), delete=False
             ) as f:
-                # We store raw tuples in the cache because pickling NamedTuples
-                # doesn't work with mypyc on Python 3.8, and because it's faster.
-                data: Dict[str, Tuple[float, int, str]] = {
+                # We store raw tuples in the cache because it's faster.
+                data: dict[str, tuple[float, int, str]] = {
                     k: (*v,) for k, v in self.file_data.items()
                 }
                 pickle.dump(data, f, protocol=4)

src/black/comments.py

@@ -1,7 +1,8 @@
 import re
+from collections.abc import Collection, Iterator
 from dataclasses import dataclass
 from functools import lru_cache
-from typing import Collection, Final, Iterator, List, Optional, Tuple, Union
+from typing import Final, Optional, Union
 
 from black.mode import Mode, Preview
 from black.nodes import (
@@ -46,6 +47,7 @@ class ProtoComment:
     newlines: int  # how many newlines before the comment
     consumed: int  # how many characters of the original leaf's prefix did we consume
     form_feed: bool  # is there a form feed before the comment
+    leading_whitespace: str  # leading whitespace before the comment, if any
 
 
 def generate_comments(leaf: LN) -> Iterator[Leaf]:
@@ -76,9 +78,9 @@ def generate_comments(leaf: LN) -> Iterator[Leaf]:
 
 
 @lru_cache(maxsize=4096)
-def list_comments(prefix: str, *, is_endmarker: bool) -> List[ProtoComment]:
+def list_comments(prefix: str, *, is_endmarker: bool) -> list[ProtoComment]:
     """Return a list of :class:`ProtoComment` objects parsed from the given `prefix`."""
-    result: List[ProtoComment] = []
+    result: list[ProtoComment] = []
     if not prefix or "#" not in prefix:
         return result
 
@@ -88,7 +90,9 @@ def list_comments(prefix: str, *, is_endmarker: bool) -> List[ProtoComment]:
     form_feed = False
     for index, full_line in enumerate(re.split("\r?\n", prefix)):
         consumed += len(full_line) + 1  # adding the length of the split '\n'
-        line = full_line.lstrip()
+        match = re.match(r"^(\s*)(\S.*|)$", full_line)
+        assert match
+        whitespace, line = match.groups()
         if not line:
             nlines += 1
             if "\f" in full_line:
@@ -113,6 +117,7 @@ def list_comments(prefix: str, *, is_endmarker: bool) -> List[ProtoComment]:
                 newlines=nlines,
                 consumed=consumed,
                 form_feed=form_feed,
+                leading_whitespace=whitespace,
             )
         )
         form_feed = False
@@ -162,7 +167,7 @@ def make_comment(content: str) -> str:
 
 
 def normalize_fmt_off(
-    node: Node, mode: Mode, lines: Collection[Tuple[int, int]]
+    node: Node, mode: Mode, lines: Collection[tuple[int, int]]
 ) -> None:
     """Convert content between `# fmt: off`/`# fmt: on` into standalone comments."""
     try_again = True
@@ -171,7 +176,7 @@ def normalize_fmt_off(
 
 
 def convert_one_fmt_off_pair(
-    node: Node, mode: Mode, lines: Collection[Tuple[int, int]]
+    node: Node, mode: Mode, lines: Collection[tuple[int, int]]
 ) -> bool:
     """Convert content of a single `# fmt: off`/`# fmt: on` into a standalone comment.
 
@@ -180,24 +185,24 @@ def convert_one_fmt_off_pair(
     for leaf in node.leaves():
         previous_consumed = 0
         for comment in list_comments(leaf.prefix, is_endmarker=False):
-            should_pass_fmt = comment.value in FMT_OFF or _contains_fmt_skip_comment(
-                comment.value, mode
-            )
-            if not should_pass_fmt:
+            is_fmt_off = comment.value in FMT_OFF
+            is_fmt_skip = _contains_fmt_skip_comment(comment.value, mode)
+            if (not is_fmt_off and not is_fmt_skip) or (
+                # Invalid use when `# fmt: off` is applied before a closing bracket.
+                is_fmt_off
+                and leaf.type in CLOSING_BRACKETS
+            ):
                 previous_consumed = comment.consumed
                 continue
             # We only want standalone comments. If there's no previous leaf or
             # the previous leaf is indentation, it's a standalone comment in
             # disguise.
-            if should_pass_fmt and comment.type != STANDALONE_COMMENT:
+            if comment.type != STANDALONE_COMMENT:
                 prev = preceding_leaf(leaf)
                 if prev:
-                    if comment.value in FMT_OFF and prev.type not in WHITESPACE:
+                    if is_fmt_off and prev.type not in WHITESPACE:
                         continue
-                    if (
-                        _contains_fmt_skip_comment(comment.value, mode)
-                        and prev.type in WHITESPACE
-                    ):
+                    if is_fmt_skip and prev.type in WHITESPACE:
                         continue
 
             ignored_nodes = list(generate_ignored_nodes(leaf, comment, mode))
@@ -209,7 +214,7 @@ def convert_one_fmt_off_pair(
             prefix = first.prefix
             if comment.value in FMT_OFF:
                 first.prefix = prefix[comment.consumed :]
-            if _contains_fmt_skip_comment(comment.value, mode):
+            if is_fmt_skip:
                 first.prefix = ""
                 standalone_comment_prefix = prefix
             else:
@@ -221,8 +226,7 @@ def convert_one_fmt_off_pair(
             if comment.value in FMT_OFF:
                 fmt_off_prefix = ""
                 if len(lines) > 0 and not any(
-                    comment_lineno >= line[0] and comment_lineno <= line[1]
-                    for line in lines
+                    line[0] <= comment_lineno <= line[1] for line in lines
                 ):
                     # keeping indentation of comment by preserving original whitespaces.
                     fmt_off_prefix = prefix.split(comment.value)[0]
@@ -230,8 +234,8 @@ def convert_one_fmt_off_pair(
                         fmt_off_prefix = fmt_off_prefix.split("\n")[-1]
                 standalone_comment_prefix += fmt_off_prefix
                 hidden_value = comment.value + "\n" + hidden_value
-            if _contains_fmt_skip_comment(comment.value, mode):
-                hidden_value += "  " + comment.value
+            if is_fmt_skip:
+                hidden_value += comment.leading_whitespace + comment.value
             if hidden_value.endswith("\n"):
                 # That happens when one of the `ignored_nodes` ended with a NEWLINE
                 # leaf (possibly followed by a DEDENT).
@@ -266,7 +270,7 @@ def generate_ignored_nodes(
     Stops at the end of the block.
     """
     if _contains_fmt_skip_comment(comment.value, mode):
-        yield from _generate_ignored_nodes_from_fmt_skip(leaf, comment)
+        yield from _generate_ignored_nodes_from_fmt_skip(leaf, comment, mode)
         return
     container: Optional[LN] = container_of(leaf)
     while container is not None and container.type != token.ENDMARKER:
@@ -305,23 +309,67 @@ def generate_ignored_nodes(
 
 
 def _generate_ignored_nodes_from_fmt_skip(
-    leaf: Leaf, comment: ProtoComment
+    leaf: Leaf, comment: ProtoComment, mode: Mode
 ) -> Iterator[LN]:
     """Generate all leaves that should be ignored by the `# fmt: skip` from `leaf`."""
     prev_sibling = leaf.prev_sibling
     parent = leaf.parent
+    ignored_nodes: list[LN] = []
     # Need to properly format the leaf prefix to compare it to comment.value,
     # which is also formatted
     comments = list_comments(leaf.prefix, is_endmarker=False)
     if not comments or comment.value != comments[0].value:
         return
     if prev_sibling is not None:
-        leaf.prefix = ""
-        siblings = [prev_sibling]
-        while "\n" not in prev_sibling.prefix and prev_sibling.prev_sibling is not None:
-            prev_sibling = prev_sibling.prev_sibling
-            siblings.insert(0, prev_sibling)
-        yield from siblings
+        leaf.prefix = leaf.prefix[comment.consumed :]
+
+        if Preview.fix_fmt_skip_in_one_liners not in mode:
+            siblings = [prev_sibling]
+            while (
+                "\n" not in prev_sibling.prefix
+                and prev_sibling.prev_sibling is not None
+            ):
+                prev_sibling = prev_sibling.prev_sibling
+                siblings.insert(0, prev_sibling)
+            yield from siblings
+            return
+
+        # Generates the nodes to be ignored by `fmt: skip`.
+
+        # Nodes to ignore are the ones on the same line as the
+        # `# fmt: skip` comment, excluding the `# fmt: skip`
+        # node itself.
+
+        # Traversal process (starting at the `# fmt: skip` node):
+        # 1. Move to the `prev_sibling` of the current node.
+        # 2. If `prev_sibling` has children, go to its rightmost leaf.
+        # 3. If there’s no `prev_sibling`, move up to the parent
+        # node and repeat.
+        # 4. Continue until:
+        #    a. You encounter an `INDENT` or `NEWLINE` node (indicates
+        #       start of the line).
+        #    b. You reach the root node.
+
+        # Include all visited LEAVES in the ignored list, except INDENT
+        # or NEWLINE leaves.
+
+        current_node = prev_sibling
+        ignored_nodes = [current_node]
+        if current_node.prev_sibling is None and current_node.parent is not None:
+            current_node = current_node.parent
+        while "\n" not in current_node.prefix and current_node.prev_sibling is not None:
+            leaf_nodes = list(current_node.prev_sibling.leaves())
+            current_node = leaf_nodes[-1] if leaf_nodes else current_node
+
+            if current_node.type in (token.NEWLINE, token.INDENT):
+                current_node.prefix = ""
+                break
+
+            ignored_nodes.insert(0, current_node)
+
+            if current_node.prev_sibling is None and current_node.parent is not None:
+                current_node = current_node.parent
+        yield from ignored_nodes
     elif (
         parent is not None and parent.type == syms.suite and leaf.type == token.NEWLINE
     ):
@@ -329,7 +377,6 @@ def _generate_ignored_nodes_from_fmt_skip(
         # statements. The ignored nodes should be previous siblings of the
         # parent suite node.
         leaf.prefix = ""
-        ignored_nodes: List[LN] = []
         parent_sibling = parent.prev_sibling
         while parent_sibling is not None and parent_sibling.type != syms.suite:
             ignored_nodes.insert(0, parent_sibling)
@@ -369,7 +416,7 @@ def children_contains_fmt_on(container: LN) -> bool:
     return False
 
 
-def contains_pragma_comment(comment_list: List[Leaf]) -> bool:
+def contains_pragma_comment(comment_list: list[Leaf]) -> bool:
     """
     Returns:
         True iff one of the comments in @comment_list is a pragma used by one
@@ -391,22 +438,18 @@ def _contains_fmt_skip_comment(comment_line: str, mode: Mode) -> bool:
       # noqa:XXX # fmt:skip # a nice line  <-- multiple comments (Preview)
       # pylint:XXX; fmt:skip               <-- list of comments (; separated, Preview)
     """
-    semantic_comment_blocks = (
-        [
-            comment_line,
-            *[
-                _COMMENT_PREFIX + comment.strip()
-                for comment in comment_line.split(_COMMENT_PREFIX)[1:]
-            ],
-            *[
-                _COMMENT_PREFIX + comment.strip()
-                for comment in comment_line.strip(_COMMENT_PREFIX).split(
-                    _COMMENT_LIST_SEPARATOR
-                )
-            ],
-        ]
-        if Preview.single_line_format_skip_with_multiple_comments in mode
-        else [comment_line]
-    )
+    semantic_comment_blocks = [
+        comment_line,
+        *[
+            _COMMENT_PREFIX + comment.strip()
+            for comment in comment_line.split(_COMMENT_PREFIX)[1:]
+        ],
+        *[
+            _COMMENT_PREFIX + comment.strip()
+            for comment in comment_line.strip(_COMMENT_PREFIX).split(
+                _COMMENT_LIST_SEPARATOR
+            )
+        ],
+    ]
 
     return any(comment in FMT_SKIP for comment in semantic_comment_blocks)

src/black/concurrency.py

@@ -10,10 +10,11 @@
 import signal
 import sys
 import traceback
+from collections.abc import Iterable
 from concurrent.futures import Executor, ProcessPoolExecutor, ThreadPoolExecutor
 from multiprocessing import Manager
 from pathlib import Path
-from typing import Any, Iterable, Optional, Set
+from typing import Any, Optional
 
 from mypy_extensions import mypyc_attr
 
@@ -69,7 +70,7 @@ def shutdown(loop: asyncio.AbstractEventLoop) -> None:
 # not ideal, but this shouldn't cause any issues ... hopefully. ~ichard26
 @mypyc_attr(patchable=True)
 def reformat_many(
-    sources: Set[Path],
+    sources: set[Path],
     fast: bool,
     write_back: WriteBack,
     mode: Mode,
@@ -119,7 +120,7 @@ def reformat_many(
 
 
 async def schedule_formatting(
-    sources: Set[Path],
+    sources: set[Path],
     fast: bool,
     write_back: WriteBack,
     mode: Mode,

src/black/debug.py

@@ -1,5 +1,6 @@
+from collections.abc import Iterator
 from dataclasses import dataclass, field
-from typing import Any, Iterator, List, TypeVar, Union
+from typing import Any, TypeVar, Union
 
 from black.nodes import Visitor
 from black.output import out
@@ -14,7 +15,7 @@
 @dataclass
 class DebugVisitor(Visitor[T]):
     tree_depth: int = 0
-    list_output: List[str] = field(default_factory=list)
+    list_output: list[str] = field(default_factory=list)
     print_output: bool = True
 
     def out(self, message: str, *args: Any, **kwargs: Any) -> None:

src/black/files.py

@@ -1,21 +1,11 @@
 import io
 import os
 import sys
+from collections.abc import Iterable, Iterator, Sequence
 from functools import lru_cache
 from pathlib import Path
-from typing import (
-    TYPE_CHECKING,
-    Any,
-    Dict,
-    Iterable,
-    Iterator,
-    List,
-    Optional,
-    Pattern,
-    Sequence,
-    Tuple,
-    Union,
-)
+from re import Pattern
+from typing import TYPE_CHECKING, Any, Optional, Union
 
 from mypy_extensions import mypyc_attr
 from packaging.specifiers import InvalidSpecifier, Specifier, SpecifierSet
@@ -42,12 +32,26 @@
     import colorama  # noqa: F401
 
 
+@lru_cache
+def _load_toml(path: Union[Path, str]) -> dict[str, Any]:
+    with open(path, "rb") as f:
+        return tomllib.load(f)
+
+
+@lru_cache
+def _cached_resolve(path: Path) -> Path:
+    return path.resolve()
+
+
 @lru_cache
 def find_project_root(
     srcs: Sequence[str], stdin_filename: Optional[str] = None
-) -> Tuple[Path, str]:
+) -> tuple[Path, str]:
     """Return a directory containing .git, .hg, or pyproject.toml.
 
+    pyproject.toml files are only considered if they contain a [tool.black]
+    section and are ignored otherwise.
+
     That directory will be a common parent of all files and directories
     passed in `srcs`.
 
@@ -61,9 +65,9 @@ def find_project_root(
     if stdin_filename is not None:
         srcs = tuple(stdin_filename if s == "-" else s for s in srcs)
     if not srcs:
-        srcs = [str(Path.cwd().resolve())]
+        srcs = [str(_cached_resolve(Path.cwd()))]
 
-    path_srcs = [Path(Path.cwd(), src).resolve() for src in srcs]
+    path_srcs = [_cached_resolve(Path(Path.cwd(), src)) for src in srcs]
 
     # A list of lists of parents for each 'src'. 'src' is included as a
     # "parent" of itself if it is a directory
@@ -84,13 +88,15 @@ def find_project_root(
             return directory, ".hg directory"
 
         if (directory / "pyproject.toml").is_file():
-            return directory, "pyproject.toml"
+            pyproject_toml = _load_toml(directory / "pyproject.toml")
+            if "black" in pyproject_toml.get("tool", {}):
+                return directory, "pyproject.toml"
 
     return directory, "file system root"
 
 
 def find_pyproject_toml(
-    path_search_start: Tuple[str, ...], stdin_filename: Optional[str] = None
+    path_search_start: tuple[str, ...], stdin_filename: Optional[str] = None
 ) -> Optional[str]:
     """Find the absolute filepath to a pyproject.toml if it exists"""
     path_project_root, _ = find_project_root(path_search_start, stdin_filename)
@@ -112,14 +118,13 @@ def find_pyproject_toml(
 
 
 @mypyc_attr(patchable=True)
-def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:
+def parse_pyproject_toml(path_config: str) -> dict[str, Any]:
     """Parse a pyproject toml file, pulling out relevant parts for Black.
 
     If parsing fails, will raise a tomllib.TOMLDecodeError.
     """
-    with open(path_config, "rb") as f:
-        pyproject_toml = tomllib.load(f)
-    config: Dict[str, Any] = pyproject_toml.get("tool", {}).get("black", {})
+    pyproject_toml = _load_toml(path_config)
+    config: dict[str, Any] = pyproject_toml.get("tool", {}).get("black", {})
     config = {k.replace("--", "").replace("-", "_"): v for k, v in config.items()}
 
     if "target_version" not in config:
@@ -131,8 +136,8 @@ def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:
 
 
 def infer_target_version(
-    pyproject_toml: Dict[str, Any]
-) -> Optional[List[TargetVersion]]:
+    pyproject_toml: dict[str, Any],
+) -> Optional[list[TargetVersion]]:
     """Infer Black's target version from the project metadata in pyproject.toml.
 
     Supports the PyPA standard format (PEP 621):
@@ -155,7 +160,7 @@ def infer_target_version(
     return None
 
 
-def parse_req_python_version(requires_python: str) -> Optional[List[TargetVersion]]:
+def parse_req_python_version(requires_python: str) -> Optional[list[TargetVersion]]:
     """Parse a version string (i.e. ``"3.7"``) to a list of TargetVersion.
 
     If parsing fails, will raise a packaging.version.InvalidVersion error.
@@ -170,7 +175,7 @@ def parse_req_python_version(requires_python: str) -> Optional[List[TargetVersio
         return None
 
 
-def parse_req_python_specifier(requires_python: str) -> Optional[List[TargetVersion]]:
+def parse_req_python_specifier(requires_python: str) -> Optional[list[TargetVersion]]:
     """Parse a specifier string (i.e. ``">=3.7,<3.10"``) to a list of TargetVersion.
 
     If parsing fails, will raise a packaging.specifiers.InvalidSpecifier error.
@@ -181,7 +186,7 @@ def parse_req_python_specifier(requires_python: str) -> Optional[List[TargetVers
         return None
 
     target_version_map = {f"3.{v.value}": v for v in TargetVersion}
-    compatible_versions: List[str] = list(specifier_set.filter(target_version_map))
+    compatible_versions: list[str] = list(specifier_set.filter(target_version_map))
     if compatible_versions:
         return [target_version_map[v] for v in compatible_versions]
     return None
@@ -229,14 +234,14 @@ def find_user_pyproject_toml() -> Path:
     else:
         config_root = os.environ.get("XDG_CONFIG_HOME", "~/.config")
         user_config_path = Path(config_root).expanduser() / "black"
-    return user_config_path.resolve()
+    return _cached_resolve(user_config_path)
 
 
 @lru_cache
 def get_gitignore(root: Path) -> PathSpec:
     """Return a PathSpec matching gitignore content if present."""
     gitignore = root / ".gitignore"
-    lines: List[str] = []
+    lines: list[str] = []
     if gitignore.is_file():
         with gitignore.open(encoding="utf-8") as gf:
             lines = gf.readlines()
@@ -247,39 +252,47 @@ def get_gitignore(root: Path) -> PathSpec:
         raise
 
 
-def normalize_path_maybe_ignore(
+def resolves_outside_root_or_cannot_stat(
     path: Path,
     root: Path,
     report: Optional[Report] = None,
-) -> Optional[str]:
-    """Normalize `path`. May return `None` if `path` was ignored.
-
-    `report` is where "path ignored" output goes.
+) -> bool:
+    """
+    Returns whether the path is a symbolic link that points outside the
+    root directory. Also returns True if we failed to resolve the path.
     """
     try:
-        abspath = path if path.is_absolute() else Path.cwd() / path
-        normalized_path = abspath.resolve()
-        try:
-            root_relative_path = normalized_path.relative_to(root).as_posix()
-        except ValueError:
-            if report:
-                report.path_ignored(
-                    path, f"is a symbolic link that points outside {root}"
-                )
-            return None
-
+        resolved_path = _cached_resolve(path)
     except OSError as e:
         if report:
             report.path_ignored(path, f"cannot be read because {e}")
-        return None
+        return True
+    try:
+        resolved_path.relative_to(root)
+    except ValueError:
+        if report:
+            report.path_ignored(path, f"is a symbolic link that points outside {root}")
+        return True
+    return False
 
-    return root_relative_path
+
+def best_effort_relative_path(path: Path, root: Path) -> Path:
+    # Precondition: resolves_outside_root_or_cannot_stat(path, root) is False
+    try:
+        return path.absolute().relative_to(root)
+    except ValueError:
+        pass
+    root_parent = next((p for p in path.parents if _cached_resolve(p) == root), None)
+    if root_parent is not None:
+        return path.relative_to(root_parent)
+    # something adversarial, fallback to path guaranteed by precondition
+    return _cached_resolve(path).relative_to(root)
 
 
 def _path_is_ignored(
     root_relative_path: str,
     root: Path,
-    gitignore_dict: Dict[Path, PathSpec],
+    gitignore_dict: dict[Path, PathSpec],
 ) -> bool:
     path = root / root_relative_path
     # Note that this logic is sensitive to the ordering of gitignore_dict. Callers must
@@ -287,6 +300,8 @@ def _path_is_ignored(
     for gitignore_path, pattern in gitignore_dict.items():
         try:
             relative_path = path.relative_to(gitignore_path).as_posix()
+            if path.is_dir():
+                relative_path = relative_path + "/"
         except ValueError:
             break
         if pattern.match_file(relative_path):
@@ -310,7 +325,7 @@ def gen_python_files(
     extend_exclude: Optional[Pattern[str]],
     force_exclude: Optional[Pattern[str]],
     report: Report,
-    gitignore_dict: Optional[Dict[Path, PathSpec]],
+    gitignore_dict: Optional[dict[Path, PathSpec]],
     *,
     verbose: bool,
     quiet: bool,
@@ -326,7 +341,8 @@ def gen_python_files(
 
     assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
     for child in paths:
-        root_relative_path = child.absolute().relative_to(root).as_posix()
+        assert child.is_absolute()
+        root_relative_path = child.relative_to(root).as_posix()
 
         # First ignore files matching .gitignore, if passed
         if gitignore_dict and _path_is_ignored(
@@ -354,8 +370,7 @@ def gen_python_files(
             report.path_ignored(child, "matches the --force-exclude regular expression")
             continue
 
-        normalized_path = normalize_path_maybe_ignore(child, root, report)
-        if normalized_path is None:
+        if resolves_outside_root_or_cannot_stat(child, root, report):
             continue
 
         if child.is_dir():

src/black/handle_ipynb_magics.py

@@ -3,17 +3,19 @@
 import ast
 import collections
 import dataclasses
+import re
 import secrets
 import sys
 from functools import lru_cache
 from importlib.util import find_spec
-from typing import Dict, List, Optional, Tuple
+from typing import Optional
 
 if sys.version_info >= (3, 10):
     from typing import TypeGuard
 else:
     from typing_extensions import TypeGuard
 
+from black.mode import Mode
 from black.output import out
 from black.report import NothingChanged
 
@@ -41,7 +43,6 @@
     "time",
     "timeit",
 ))
-TOKEN_HEX = secrets.token_hex
 
 
 @dataclasses.dataclass(frozen=True)
@@ -64,7 +65,35 @@ def jupyter_dependencies_are_installed(*, warn: bool) -> bool:
     return installed
 
 
-def remove_trailing_semicolon(src: str) -> Tuple[str, bool]:
+def validate_cell(src: str, mode: Mode) -> None:
+    """Check that cell does not already contain TransformerManager transformations,
+    or non-Python cell magics, which might cause tokenizer_rt to break because of
+    indentations.
+
+    If a cell contains ``!ls``, then it'll be transformed to
+    ``get_ipython().system('ls')``. However, if the cell originally contained
+    ``get_ipython().system('ls')``, then it would get transformed in the same way:
+
+        >>> TransformerManager().transform_cell("get_ipython().system('ls')")
+        "get_ipython().system('ls')\n"
+        >>> TransformerManager().transform_cell("!ls")
+        "get_ipython().system('ls')\n"
+
+    Due to the impossibility of safely roundtripping in such situations, cells
+    containing transformed magics will be ignored.
+    """
+    if any(transformed_magic in src for transformed_magic in TRANSFORMED_MAGICS):
+        raise NothingChanged
+
+    line = _get_code_start(src)
+    if line.startswith("%%") and (
+        line.split(maxsplit=1)[0][2:]
+        not in PYTHON_CELL_MAGICS | mode.python_cell_magics
+    ):
+        raise NothingChanged
+
+
+def remove_trailing_semicolon(src: str) -> tuple[str, bool]:
     """Remove trailing semicolon from Jupyter notebook cell.
 
     For example,
@@ -120,7 +149,7 @@ def put_trailing_semicolon_back(src: str, has_trailing_semicolon: bool) -> str:
     return str(tokens_to_src(tokens))
 
 
-def mask_cell(src: str) -> Tuple[str, List[Replacement]]:
+def mask_cell(src: str) -> tuple[str, list[Replacement]]:
     """Mask IPython magics so content becomes parseable Python code.
 
     For example,
@@ -130,12 +159,12 @@ def mask_cell(src: str) -> Tuple[str, List[Replacement]]:
 
     becomes
 
-        "25716f358c32750e"
+        b"25716f358c32750"
         'foo'
 
     The replacements are returned, along with the transformed code.
     """
-    replacements: List[Replacement] = []
+    replacements: list[Replacement] = []
     try:
         ast.parse(src)
     except SyntaxError:
@@ -148,18 +177,32 @@ def mask_cell(src: str) -> Tuple[str, List[Replacement]]:
     from IPython.core.inputtransformer2 import TransformerManager
 
     transformer_manager = TransformerManager()
+    # A side effect of the following transformation is that it also removes any
+    # empty lines at the beginning of the cell.
     transformed = transformer_manager.transform_cell(src)
     transformed, cell_magic_replacements = replace_cell_magics(transformed)
     replacements += cell_magic_replacements
     transformed = transformer_manager.transform_cell(transformed)
     transformed, magic_replacements = replace_magics(transformed)
-    if len(transformed.splitlines()) != len(src.splitlines()):
+    if len(transformed.strip().splitlines()) != len(src.strip().splitlines()):
         # Multi-line magic, not supported.
         raise NothingChanged
     replacements += magic_replacements
     return transformed, replacements
 
 
+def create_token(n_chars: int) -> str:
+    """Create a randomly generated token that is n_chars characters long."""
+    assert n_chars > 0
+    n_bytes = max(n_chars // 2 - 1, 1)
+    token = secrets.token_hex(n_bytes)
+    if len(token) + 3 > n_chars:
+        token = token[:-1]
+    # We use a bytestring so that the string does not get interpreted
+    # as a docstring.
+    return f'b"{token}"'
+
+
 def get_token(src: str, magic: str) -> str:
     """Return randomly generated token to mask IPython magic with.
 
@@ -169,11 +212,11 @@ def get_token(src: str, magic: str) -> str:
     not already present anywhere else in the cell.
     """
     assert magic
-    nbytes = max(len(magic) // 2 - 1, 1)
-    token = TOKEN_HEX(nbytes)
+    n_chars = len(magic)
+    token = create_token(n_chars)
     counter = 0
     while token in src:
-        token = TOKEN_HEX(nbytes)
+        token = create_token(n_chars)
         counter += 1
         if counter > 100:
             raise AssertionError(
@@ -181,12 +224,10 @@ def get_token(src: str, magic: str) -> str:
                 "Please report a bug on https://github.com/psf/black/issues.  "
                 f"The magic might be helpful: {magic}"
             ) from None
-    if len(token) + 2 < len(magic):
-        token = f"{token}."
-    return f'"{token}"'
+    return token
 
 
-def replace_cell_magics(src: str) -> Tuple[str, List[Replacement]]:
+def replace_cell_magics(src: str) -> tuple[str, list[Replacement]]:
     """Replace cell magic with token.
 
     Note that 'src' will already have been processed by IPython's
@@ -203,7 +244,7 @@ def replace_cell_magics(src: str) -> Tuple[str, List[Replacement]]:
 
     The replacement, along with the transformed code, is returned.
     """
-    replacements: List[Replacement] = []
+    replacements: list[Replacement] = []
 
     tree = ast.parse(src)
 
@@ -217,7 +258,7 @@ def replace_cell_magics(src: str) -> Tuple[str, List[Replacement]]:
     return f"{mask}\n{cell_magic_finder.cell_magic.body}", replacements
 
 
-def replace_magics(src: str) -> Tuple[str, List[Replacement]]:
+def replace_magics(src: str) -> tuple[str, list[Replacement]]:
     """Replace magics within body of cell.
 
     Note that 'src' will already have been processed by IPython's
@@ -239,7 +280,7 @@ def replace_magics(src: str) -> Tuple[str, List[Replacement]]:
     magic_finder = MagicFinder()
     magic_finder.visit(ast.parse(src))
     new_srcs = []
-    for i, line in enumerate(src.splitlines(), start=1):
+    for i, line in enumerate(src.split("\n"), start=1):
         if i in magic_finder.magics:
             offsets_and_magics = magic_finder.magics[i]
             if len(offsets_and_magics) != 1:  # pragma: nocover
@@ -258,7 +299,7 @@ def replace_magics(src: str) -> Tuple[str, List[Replacement]]:
     return "\n".join(new_srcs), replacements
 
 
-def unmask_cell(src: str, replacements: List[Replacement]) -> str:
+def unmask_cell(src: str, replacements: list[Replacement]) -> str:
     """Remove replacements from cell.
 
     For example
@@ -276,6 +317,21 @@ def unmask_cell(src: str, replacements: List[Replacement]) -> str:
     return src
 
 
+def _get_code_start(src: str) -> str:
+    """Provides the first line where the code starts.
+
+    Iterates over lines of code until it finds the first line that doesn't
+    contain only empty spaces and comments. It removes any empty spaces at the
+    start of the line and returns it. If such line doesn't exist, it returns an
+    empty string.
+    """
+    for match in re.finditer(".+", src):
+        line = match.group(0).lstrip()
+        if line and not line.startswith("#"):
+            return line
+    return ""
+
+
 def _is_ipython_magic(node: ast.expr) -> TypeGuard[ast.Attribute]:
     """Check if attribute is IPython magic.
 
@@ -291,11 +347,11 @@ def _is_ipython_magic(node: ast.expr) -> TypeGuard[ast.Attribute]:
     )
 
 
-def _get_str_args(args: List[ast.expr]) -> List[str]:
+def _get_str_args(args: list[ast.expr]) -> list[str]:
     str_args = []
     for arg in args:
-        assert isinstance(arg, ast.Str)
-        str_args.append(arg.s)
+        assert isinstance(arg, ast.Constant) and isinstance(arg.value, str)
+        str_args.append(arg.value)
     return str_args
 
 
@@ -375,7 +431,7 @@ class MagicFinder(ast.NodeVisitor):
     """
 
     def __init__(self) -> None:
-        self.magics: Dict[int, List[OffsetAndMagic]] = collections.defaultdict(list)
+        self.magics: dict[int, list[OffsetAndMagic]] = collections.defaultdict(list)
 
     def visit_Assign(self, node: ast.Assign) -> None:
         """Look for system assign magics.

src/black/linegen.py

@@ -4,14 +4,16 @@
 
 import re
 import sys
+from collections.abc import Collection, Iterator
 from dataclasses import replace
 from enum import Enum, auto
 from functools import partial, wraps
-from typing import Collection, Iterator, List, Optional, Set, Union, cast
+from typing import Optional, Union, cast
 
 from black.brackets import (
     COMMA_PRIORITY,
     DOT_PRIORITY,
+    STRING_PRIORITY,
     get_leaves_inside_matching_brackets,
     max_delimiter_priority_in_atom,
 )
@@ -31,26 +33,32 @@
     BRACKETS,
     CLOSING_BRACKETS,
     OPENING_BRACKETS,
-    RARROW,
     STANDALONE_COMMENT,
     STATEMENT,
     WHITESPACE,
     Visitor,
     ensure_visible,
+    fstring_to_string,
+    get_annotation_type,
+    has_sibling_with_type,
     is_arith_like,
     is_async_stmt_or_funcdef,
     is_atom_with_invisible_parens,
     is_docstring,
     is_empty_tuple,
-    is_function_or_class,
+    is_generator,
     is_lpar_token,
     is_multiline_string,
     is_name_token,
     is_one_sequence_between,
     is_one_tuple,
+    is_parent_function_or_class,
+    is_part_of_annotation,
     is_rpar_token,
     is_stub_body,
     is_stub_suite,
+    is_tuple,
+    is_tuple_containing_star,
     is_tuple_containing_walrus,
     is_type_ignore_comment_string,
     is_vararg,
@@ -61,7 +69,7 @@
 )
 from black.numerics import normalize_numeric_literal
 from black.strings import (
-    fix_docstring,
+    fix_multiline_docstring,
     get_string_prefix,
     normalize_string_prefix,
     normalize_string_quotes,
@@ -115,10 +123,8 @@ def line(self, indent: int = 0) -> Iterator[Line]:
             self.current_line.depth += indent
             return  # Line is empty, don't emit. Creating a new one unnecessary.
 
-        if (
-            Preview.improved_async_statements_handling in self.mode
-            and len(self.current_line.leaves) == 1
-            and is_async_stmt_or_funcdef(self.current_line.leaves[0])
+        if len(self.current_line.leaves) == 1 and is_async_stmt_or_funcdef(
+            self.current_line.leaves[0]
         ):
             # Special case for async def/for/with statements. `visit_async_stmt`
             # adds an `ASYNC` leaf then visits the child def/for/with statement
@@ -152,11 +158,6 @@ def visit_default(self, node: LN) -> Iterator[Line]:
 
             if any_open_brackets:
                 node.prefix = ""
-            if self.mode.string_normalization and node.type == token.STRING:
-                node.value = normalize_string_prefix(node.value)
-                node.value = normalize_string_quotes(node.value)
-            if node.type == token.NUMBER:
-                normalize_numeric_literal(node)
             if node.type not in WHITESPACE:
                 self.current_line.append(node)
         yield from super().visit_default(node)
@@ -164,16 +165,19 @@ def visit_default(self, node: LN) -> Iterator[Line]:
     def visit_test(self, node: Node) -> Iterator[Line]:
         """Visit an `x if y else z` test"""
 
-        if Preview.parenthesize_conditional_expressions in self.mode:
-            already_parenthesized = (
-                node.prev_sibling and node.prev_sibling.type == token.LPAR
-            )
+        already_parenthesized = (
+            node.prev_sibling and node.prev_sibling.type == token.LPAR
+        )
 
-            if not already_parenthesized:
-                lpar = Leaf(token.LPAR, "")
-                rpar = Leaf(token.RPAR, "")
-                node.insert_child(0, lpar)
-                node.append_child(rpar)
+        if not already_parenthesized:
+            # Similar to logic in wrap_in_parentheses
+            lpar = Leaf(token.LPAR, "")
+            rpar = Leaf(token.RPAR, "")
+            prefix = node.prefix
+            node.prefix = ""
+            lpar.prefix = prefix
+            node.insert_child(0, lpar)
+            node.append_child(rpar)
 
         yield from self.visit_default(node)
 
@@ -198,7 +202,7 @@ def visit_DEDENT(self, node: Leaf) -> Iterator[Line]:
         yield from self.line(-1)
 
     def visit_stmt(
-        self, node: Node, keywords: Set[str], parens: Set[str]
+        self, node: Node, keywords: set[str], parens: set[str]
     ) -> Iterator[Line]:
         """Visit a statement.
 
@@ -238,13 +242,16 @@ def visit_dictsetmaker(self, node: Node) -> Iterator[Line]:
                 if i == 0:
                     continue
                 if node.children[i - 1].type == token.COLON:
-                    if child.type == syms.atom and child.children[0].type == token.LPAR:
-                        if maybe_make_parens_invisible_in_atom(
+                    if (
+                        child.type == syms.atom
+                        and child.children[0].type in OPENING_BRACKETS
+                        and not is_walrus_assignment(child)
+                    ):
+                        maybe_make_parens_invisible_in_atom(
                             child,
                             parent=node,
                             remove_brackets_around_comma=False,
-                        ):
-                            wrap_in_parentheses(node, child, visible=False)
+                        )
                     else:
                         wrap_in_parentheses(node, child, visible=False)
         yield from self.visit_default(node)
@@ -285,9 +292,7 @@ def visit_match_case(self, node: Node) -> Iterator[Line]:
 
     def visit_suite(self, node: Node) -> Iterator[Line]:
         """Visit a suite."""
-        if (
-            self.mode.is_pyi or Preview.dummy_implementations in self.mode
-        ) and is_stub_suite(node, self.mode):
+        if is_stub_suite(node):
             yield from self.visit(node.children[2])
         else:
             yield from self.visit_default(node)
@@ -301,11 +306,7 @@ def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
             prev_type = child.type
 
         if node.parent and node.parent.type in STATEMENT:
-            if Preview.dummy_implementations in self.mode:
-                condition = is_function_or_class(node.parent)
-            else:
-                condition = self.mode.is_pyi
-            if condition and is_stub_body(node):
+            if is_parent_function_or_class(node) and is_stub_body(node):
                 yield from self.visit_default(node)
             else:
                 yield from self.line(+1)
@@ -313,12 +314,11 @@ def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
                 yield from self.line(-1)
 
         else:
-            if (
-                not (self.mode.is_pyi or Preview.dummy_implementations in self.mode)
-                or not node.parent
-                or not is_stub_suite(node.parent, self.mode)
-            ):
-                yield from self.line()
+            if node.parent and is_stub_suite(node.parent):
+                node.prefix = ""
+                yield from self.visit_default(node)
+                return
+            yield from self.line()
             yield from self.visit_default(node)
 
     def visit_async_stmt(self, node: Node) -> Iterator[Line]:
@@ -335,11 +335,7 @@ def visit_async_stmt(self, node: Node) -> Iterator[Line]:
                 break
 
         internal_stmt = next(children)
-        if Preview.improved_async_statements_handling in self.mode:
-            yield from self.visit(internal_stmt)
-        else:
-            for child in internal_stmt.children:
-                yield from self.visit(child)
+        yield from self.visit(internal_stmt)
 
     def visit_decorators(self, node: Node) -> Iterator[Line]:
         """Visit decorators."""
@@ -413,28 +409,25 @@ def foo(a: int, b: float = 7): ...
 
         def foo(a: (int), b: (float) = 7): ...
         """
-        if Preview.parenthesize_long_type_hints in self.mode:
-            assert len(node.children) == 3
-            if maybe_make_parens_invisible_in_atom(node.children[2], parent=node):
-                wrap_in_parentheses(node, node.children[2], visible=False)
+        assert len(node.children) == 3
+        if maybe_make_parens_invisible_in_atom(node.children[2], parent=node):
+            wrap_in_parentheses(node, node.children[2], visible=False)
 
         yield from self.visit_default(node)
 
     def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
-        if Preview.hex_codes_in_unicode_sequences in self.mode:
-            normalize_unicode_escape_sequences(leaf)
+        normalize_unicode_escape_sequences(leaf)
 
         if is_docstring(leaf) and not re.search(r"\\\s*\n", leaf.value):
             # We're ignoring docstrings with backslash newline escapes because changing
             # indentation of those changes the AST representation of the code.
             if self.mode.string_normalization:
                 docstring = normalize_string_prefix(leaf.value)
-                # visit_default() does handle string normalization for us, but
-                # since this method acts differently depending on quote style (ex.
+                # We handle string normalization at the end of this method, but since
+                # what we do right now acts differently depending on quote style (ex.
                 # see padding logic below), there's a possibility for unstable
-                # formatting as visit_default() is called *after*. To avoid a
-                # situation where this function formats a docstring differently on
-                # the second pass, normalize it early.
+                # formatting. To avoid a situation where this function formats a
+                # docstring differently on the second pass, normalize it early.
                 docstring = normalize_string_quotes(docstring)
             else:
                 docstring = leaf.value
@@ -452,7 +445,7 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
             indent = " " * 4 * self.current_line.depth
 
             if is_multiline_string(leaf):
-                docstring = fix_docstring(docstring, indent)
+                docstring = fix_multiline_docstring(docstring, indent)
             else:
                 docstring = docstring.strip()
 
@@ -477,7 +470,7 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
             quote = quote_char * quote_len
 
             # It's invalid to put closing single-character quotes on a new line.
-            if self.mode and quote_len == 3:
+            if quote_len == 3:
                 # We need to find the length of the last line of the docstring
                 # to find if we can add the closing quotes to the line without
                 # exceeding the maximum line length.
@@ -487,28 +480,100 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
                 last_line_length = len(lines[-1]) if docstring else 0
 
                 # If adding closing quotes would cause the last line to exceed
-                # the maximum line length then put a line break before the
-                # closing quotes
+                # the maximum line length, and the closing quote is not
+                # prefixed by a newline then put a line break before
+                # the closing quotes
                 if (
                     len(lines) > 1
                     and last_line_length + quote_len > self.mode.line_length
                     and len(indent) + quote_len <= self.mode.line_length
                     and not has_trailing_backslash
                 ):
-                    leaf.value = prefix + quote + docstring + "\n" + indent + quote
+                    if leaf.value[-1 - quote_len] == "\n":
+                        leaf.value = prefix + quote + docstring + quote
+                    else:
+                        leaf.value = prefix + quote + docstring + "\n" + indent + quote
                 else:
                     leaf.value = prefix + quote + docstring + quote
             else:
                 leaf.value = prefix + quote + docstring + quote
 
+        if self.mode.string_normalization and leaf.type == token.STRING:
+            leaf.value = normalize_string_prefix(leaf.value)
+            leaf.value = normalize_string_quotes(leaf.value)
         yield from self.visit_default(leaf)
 
+    def visit_NUMBER(self, leaf: Leaf) -> Iterator[Line]:
+        normalize_numeric_literal(leaf)
+        yield from self.visit_default(leaf)
+
+    def visit_atom(self, node: Node) -> Iterator[Line]:
+        """Visit any atom"""
+        if len(node.children) == 3:
+            first = node.children[0]
+            last = node.children[-1]
+            if (first.type == token.LSQB and last.type == token.RSQB) or (
+                first.type == token.LBRACE and last.type == token.RBRACE
+            ):
+                # Lists or sets of one item
+                maybe_make_parens_invisible_in_atom(node.children[1], parent=node)
+
+        yield from self.visit_default(node)
+
+    def visit_fstring(self, node: Node) -> Iterator[Line]:
+        # currently we don't want to format and split f-strings at all.
+        string_leaf = fstring_to_string(node)
+        node.replace(string_leaf)
+        if "\\" in string_leaf.value and any(
+            "\\" in str(child)
+            for child in node.children
+            if child.type == syms.fstring_replacement_field
+        ):
+            # string normalization doesn't account for nested quotes,
+            # causing breakages. skip normalization when nested quotes exist
+            yield from self.visit_default(string_leaf)
+            return
+        yield from self.visit_STRING(string_leaf)
+
+        # TODO: Uncomment Implementation to format f-string children
+        # fstring_start = node.children[0]
+        # fstring_end = node.children[-1]
+        # assert isinstance(fstring_start, Leaf)
+        # assert isinstance(fstring_end, Leaf)
+
+        # quote_char = fstring_end.value[0]
+        # quote_idx = fstring_start.value.index(quote_char)
+        # prefix, quote = (
+        #     fstring_start.value[:quote_idx],
+        #     fstring_start.value[quote_idx:]
+        # )
+
+        # if not is_docstring(node, self.mode):
+        #     prefix = normalize_string_prefix(prefix)
+
+        # assert quote == fstring_end.value
+
+        # is_raw_fstring = "r" in prefix or "R" in prefix
+        # middles = [
+        #     leaf
+        #     for leaf in node.leaves()
+        #     if leaf.type == token.FSTRING_MIDDLE
+        # ]
+
+        # if self.mode.string_normalization:
+        #     middles, quote = normalize_fstring_quotes(quote, middles, is_raw_fstring)
+
+        # fstring_start.value = prefix + quote
+        # fstring_end.value = quote
+
+        # yield from self.visit_default(node)
+
     def __post_init__(self) -> None:
         """You are in a twisty little maze of passages."""
         self.current_line = Line(mode=self.mode)
 
         v = self.visit_stmt
-        Ø: Set[str] = set()
+        Ø: set[str] = set()
         self.visit_assert_stmt = partial(v, keywords={"assert"}, parens={"assert", ","})
         self.visit_if_stmt = partial(
             v, keywords={"if", "else", "elif"}, parens={"if", "elif"}
@@ -522,13 +587,7 @@ def __post_init__(self) -> None:
         self.visit_with_stmt = partial(v, keywords={"with"}, parens={"with"})
         self.visit_classdef = partial(v, keywords={"class"}, parens=Ø)
 
-        # When this is moved out of preview, add ":" directly to ASSIGNMENTS in nodes.py
-        if Preview.parenthesize_long_type_hints in self.mode:
-            assignments = ASSIGNMENTS | {":"}
-        else:
-            assignments = ASSIGNMENTS
-        self.visit_expr_stmt = partial(v, keywords=Ø, parens=assignments)
-
+        self.visit_expr_stmt = partial(v, keywords=Ø, parens=ASSIGNMENTS)
         self.visit_return_stmt = partial(v, keywords={"return"}, parens={"return"})
         self.visit_import_from = partial(v, keywords=Ø, parens={"import"})
         self.visit_del_stmt = partial(v, keywords=Ø, parens={"del"})
@@ -538,6 +597,7 @@ def __post_init__(self) -> None:
         # PEP 634
         self.visit_match_stmt = self.visit_match_case
         self.visit_case_block = self.visit_match_case
+        self.visit_guard = partial(v, keywords=Ø, parens={"if"})
 
 
 def _hugging_power_ops_line_to_string(
@@ -569,9 +629,7 @@ def transform_line(
     # We need the line string when power operators are hugging to determine if we should
     # split the line. Default to line_str, if no power operator are present on the line.
     line_str_hugging_power_ops = (
-        (_hugging_power_ops_line_to_string(line, features, mode) or line_str)
-        if Preview.fix_power_op_line_length in mode
-        else line_str
+        _hugging_power_ops_line_to_string(line, features, mode) or line_str
     )
 
     ll = mode.line_length
@@ -581,7 +639,7 @@ def transform_line(
     string_split = StringSplitter(ll, sn)
     string_paren_wrap = StringParenWrapper(ll, sn)
 
-    transformers: List[Transformer]
+    transformers: list[Transformer]
     if (
         not line.contains_uncollapsable_type_comments()
         and not line.should_split_rhs
@@ -681,10 +739,7 @@ def should_split_funcdef_with_rhs(line: Line, mode: Mode) -> bool:
     """If a funcdef has a magic trailing comma in the return type, then we should first
     split the line with rhs to respect the comma.
     """
-    if Preview.respect_magic_trailing_comma_in_return_type not in mode:
-        return False
-
-    return_type_leaves: List[Leaf] = []
+    return_type_leaves: list[Leaf] = []
     in_return_type = False
 
     for leaf in line.leaves:
@@ -726,26 +781,29 @@ def left_hand_split(
     Prefer RHS otherwise.  This is why this function is not symmetrical with
     :func:`right_hand_split` which also handles optional parentheses.
     """
-    tail_leaves: List[Leaf] = []
-    body_leaves: List[Leaf] = []
-    head_leaves: List[Leaf] = []
-    current_leaves = head_leaves
-    matching_bracket: Optional[Leaf] = None
-    for leaf in line.leaves:
-        if (
-            current_leaves is body_leaves
-            and leaf.type in CLOSING_BRACKETS
-            and leaf.opening_bracket is matching_bracket
-            and isinstance(matching_bracket, Leaf)
-        ):
-            ensure_visible(leaf)
-            ensure_visible(matching_bracket)
-            current_leaves = tail_leaves if body_leaves else head_leaves
-        current_leaves.append(leaf)
-        if current_leaves is head_leaves:
-            if leaf.type in OPENING_BRACKETS:
-                matching_bracket = leaf
-                current_leaves = body_leaves
+    for leaf_type in [token.LPAR, token.LSQB]:
+        tail_leaves: list[Leaf] = []
+        body_leaves: list[Leaf] = []
+        head_leaves: list[Leaf] = []
+        current_leaves = head_leaves
+        matching_bracket: Optional[Leaf] = None
+        for leaf in line.leaves:
+            if (
+                current_leaves is body_leaves
+                and leaf.type in CLOSING_BRACKETS
+                and leaf.opening_bracket is matching_bracket
+                and isinstance(matching_bracket, Leaf)
+            ):
+                ensure_visible(leaf)
+                ensure_visible(matching_bracket)
+                current_leaves = tail_leaves if body_leaves else head_leaves
+            current_leaves.append(leaf)
+            if current_leaves is head_leaves:
+                if leaf.type == leaf_type:
+                    matching_bracket = leaf
+                    current_leaves = body_leaves
+        if matching_bracket and tail_leaves:
+            break
     if not matching_bracket or not tail_leaves:
         raise CannotSplit("No brackets found")
 
@@ -794,9 +852,9 @@ def _first_right_hand_split(
     _maybe_split_omitting_optional_parens to get an opinion whether to prefer
     splitting on the right side of an assignment statement.
     """
-    tail_leaves: List[Leaf] = []
-    body_leaves: List[Leaf] = []
-    head_leaves: List[Leaf] = []
+    tail_leaves: list[Leaf] = []
+    body_leaves: list[Leaf] = []
+    head_leaves: list[Leaf] = []
     current_leaves = tail_leaves
     opening_bracket: Optional[Leaf] = None
     closing_bracket: Optional[Leaf] = None
@@ -827,8 +885,8 @@ def _first_right_hand_split(
         and tail_leaves[0].opening_bracket is head_leaves[-1]
     ):
         inner_body_leaves = list(body_leaves)
-        hugged_opening_leaves: List[Leaf] = []
-        hugged_closing_leaves: List[Leaf] = []
+        hugged_opening_leaves: list[Leaf] = []
+        hugged_closing_leaves: list[Leaf] = []
         is_unpacking = body_leaves[0].type in [token.STAR, token.DOUBLESTAR]
         unpacking_offset: int = 1 if is_unpacking else 0
         while (
@@ -912,33 +970,7 @@ def _maybe_split_omitting_optional_parens(
         try:
             # The RHSResult Omitting Optional Parens.
             rhs_oop = _first_right_hand_split(line, omit=omit)
-            prefer_splitting_rhs_mode = (
-                Preview.prefer_splitting_right_hand_side_of_assignments in line.mode
-            )
-            is_split_right_after_equal = (
-                len(rhs.head.leaves) >= 2 and rhs.head.leaves[-2].type == token.EQUAL
-            )
-            rhs_head_contains_brackets = any(
-                leaf.type in BRACKETS for leaf in rhs.head.leaves[:-1]
-            )
-            # the -1 is for the ending optional paren
-            rhs_head_short_enough = is_line_short_enough(
-                rhs.head, mode=replace(mode, line_length=mode.line_length - 1)
-            )
-            rhs_head_explode_blocked_by_magic_trailing_comma = (
-                rhs.head.magic_trailing_comma is None
-            )
-            if (
-                not (
-                    prefer_splitting_rhs_mode
-                    and is_split_right_after_equal
-                    and rhs_head_contains_brackets
-                    and rhs_head_short_enough
-                    and rhs_head_explode_blocked_by_magic_trailing_comma
-                )
-                # the omit optional parens split is preferred by some other reason
-                or _prefer_split_rhs_oop_over_rhs(rhs_oop, rhs, mode)
-            ):
+            if _prefer_split_rhs_oop_over_rhs(rhs_oop, rhs, mode):
                 yield from _maybe_split_omitting_optional_parens(
                     rhs_oop, line, mode, features=features, omit=omit
                 )
@@ -949,8 +981,15 @@ def _maybe_split_omitting_optional_parens(
             if line.is_chained_assignment:
                 pass
 
-            elif not can_be_split(rhs.body) and not is_line_short_enough(
-                rhs.body, mode=mode
+            elif (
+                not can_be_split(rhs.body)
+                and not is_line_short_enough(rhs.body, mode=mode)
+                and not (
+                    Preview.wrap_long_dict_values_in_parens
+                    and rhs.opening_bracket.parent
+                    and rhs.opening_bracket.parent.parent
+                    and rhs.opening_bracket.parent.parent.type == syms.dictsetmaker
+                )
             ):
                 raise CannotSplit(
                     "Splitting failed, body is still too long and can't be split."
@@ -981,6 +1020,44 @@ def _prefer_split_rhs_oop_over_rhs(
     Returns whether we should prefer the result from a split omitting optional parens
     (rhs_oop) over the original (rhs).
     """
+    # contains unsplittable type ignore
+    if (
+        rhs_oop.head.contains_unsplittable_type_ignore()
+        or rhs_oop.body.contains_unsplittable_type_ignore()
+        or rhs_oop.tail.contains_unsplittable_type_ignore()
+    ):
+        return True
+
+    # Retain optional parens around dictionary values
+    if (
+        Preview.wrap_long_dict_values_in_parens
+        and rhs.opening_bracket.parent
+        and rhs.opening_bracket.parent.parent
+        and rhs.opening_bracket.parent.parent.type == syms.dictsetmaker
+        and rhs.body.bracket_tracker.delimiters
+    ):
+        # Unless the split is inside the key
+        return any(leaf.type == token.COLON for leaf in rhs_oop.tail.leaves)
+
+    # the split is right after `=`
+    if not (len(rhs.head.leaves) >= 2 and rhs.head.leaves[-2].type == token.EQUAL):
+        return True
+
+    # the left side of assignment contains brackets
+    if not any(leaf.type in BRACKETS for leaf in rhs.head.leaves[:-1]):
+        return True
+
+    # the left side of assignment is short enough (the -1 is for the ending optional
+    # paren)
+    if not is_line_short_enough(
+        rhs.head, mode=replace(mode, line_length=mode.line_length - 1)
+    ):
+        return True
+
+    # the left side of assignment won't explode further because of magic trailing comma
+    if rhs.head.magic_trailing_comma is not None:
+        return True
+
     # If we have multiple targets, we prefer more `=`s on the head vs pushing them to
     # the body
     rhs_head_equal_count = [leaf.type for leaf in rhs.head.leaves].count(token.EQUAL)
@@ -1008,10 +1085,6 @@ def _prefer_split_rhs_oop_over_rhs(
             # the first line is short enough
             and is_line_short_enough(rhs_oop.head, mode=mode)
         )
-        # contains unsplittable type ignore
-        or rhs_oop.head.contains_unsplittable_type_ignore()
-        or rhs_oop.body.contains_unsplittable_type_ignore()
-        or rhs_oop.tail.contains_unsplittable_type_ignore()
     )
 
 
@@ -1041,8 +1114,44 @@ def bracket_split_succeeded_or_raise(head: Line, body: Line, tail: Line) -> None
             )
 
 
+def _ensure_trailing_comma(
+    leaves: list[Leaf], original: Line, opening_bracket: Leaf
+) -> bool:
+    if not leaves:
+        return False
+    # Ensure a trailing comma for imports
+    if original.is_import:
+        return True
+    # ...and standalone function arguments
+    if not original.is_def:
+        return False
+    if opening_bracket.value != "(":
+        return False
+    # Don't add commas if we already have any commas
+    if any(
+        leaf.type == token.COMMA and not is_part_of_annotation(leaf) for leaf in leaves
+    ):
+        return False
+
+    # Find a leaf with a parent (comments don't have parents)
+    leaf_with_parent = next((leaf for leaf in leaves if leaf.parent), None)
+    if leaf_with_parent is None:
+        return True
+    # Don't add commas inside parenthesized return annotations
+    if get_annotation_type(leaf_with_parent) == "return":
+        return False
+    # Don't add commas inside PEP 604 unions
+    if (
+        leaf_with_parent.parent
+        and leaf_with_parent.parent.next_sibling
+        and leaf_with_parent.parent.next_sibling.type == token.VBAR
+    ):
+        return False
+    return True
+
+
 def bracket_split_build_line(
-    leaves: List[Leaf],
+    leaves: list[Leaf],
     original: Line,
     opening_bracket: Leaf,
     *,
@@ -1061,47 +1170,17 @@ def bracket_split_build_line(
     if component is _BracketSplitComponent.body:
         result.inside_brackets = True
         result.depth += 1
-        if leaves:
-            # Ensure a trailing comma for imports and standalone function arguments, but
-            # be careful not to add one after any comments or within type annotations.
-            no_commas = (
-                original.is_def
-                and opening_bracket.value == "("
-                and not any(leaf.type == token.COMMA for leaf in leaves)
-                # In particular, don't add one within a parenthesized return annotation.
-                # Unfortunately the indicator we're in a return annotation (RARROW) may
-                # be defined directly in the parent node, the parent of the parent ...
-                # and so on depending on how complex the return annotation is.
-                # This isn't perfect and there's some false negatives but they are in
-                # contexts were a comma is actually fine.
-                and not any(
-                    node.prev_sibling.type == RARROW
-                    for node in (
-                        leaves[0].parent,
-                        getattr(leaves[0].parent, "parent", None),
-                    )
-                    if isinstance(node, Node) and isinstance(node.prev_sibling, Leaf)
-                )
-                # Except the false negatives above for PEP 604 unions where we
-                # can't add the comma.
-                and not (
-                    leaves[0].parent
-                    and leaves[0].parent.next_sibling
-                    and leaves[0].parent.next_sibling.type == token.VBAR
-                )
-            )
+        if _ensure_trailing_comma(leaves, original, opening_bracket):
+            for i in range(len(leaves) - 1, -1, -1):
+                if leaves[i].type == STANDALONE_COMMENT:
+                    continue
 
-            if original.is_import or no_commas:
-                for i in range(len(leaves) - 1, -1, -1):
-                    if leaves[i].type == STANDALONE_COMMENT:
-                        continue
+                if leaves[i].type != token.COMMA:
+                    new_comma = Leaf(token.COMMA, ",")
+                    leaves.insert(i + 1, new_comma)
+                break
 
-                    if leaves[i].type != token.COMMA:
-                        new_comma = Leaf(token.COMMA, ",")
-                        leaves.insert(i + 1, new_comma)
-                    break
-
-    leaves_to_track: Set[LeafID] = set()
+    leaves_to_track: set[LeafID] = set()
     if component is _BracketSplitComponent.head:
         leaves_to_track = get_leaves_inside_matching_brackets(leaves)
     # Populate the line
@@ -1144,6 +1223,14 @@ def _get_last_non_comment_leaf(line: Line) -> Optional[int]:
     return None
 
 
+def _can_add_trailing_comma(leaf: Leaf, features: Collection[Feature]) -> bool:
+    if is_vararg(leaf, within={syms.typedargslist}):
+        return Feature.TRAILING_COMMA_IN_DEF in features
+    if is_vararg(leaf, within={syms.arglist, syms.argument}):
+        return Feature.TRAILING_COMMA_IN_CALL in features
+    return True
+
+
 def _safe_add_trailing_comma(safe: bool, delimiter_priority: int, line: Line) -> Line:
     if (
         safe
@@ -1156,6 +1243,9 @@ def _safe_add_trailing_comma(safe: bool, delimiter_priority: int, line: Line) ->
     return line
 
 
+MIGRATE_COMMENT_DELIMITERS = {STRING_PRIORITY, COMMA_PRIORITY}
+
+
 @dont_increase_indentation
 def delimiter_split(
     line: Line, features: Collection[Feature], mode: Mode
@@ -1165,10 +1255,9 @@ def delimiter_split(
     If the appropriate Features are given, the split will add trailing commas
     also in function signatures and calls that contain `*` and `**`.
     """
-    try:
-        last_leaf = line.leaves[-1]
-    except IndexError:
+    if len(line.leaves) == 0:
         raise CannotSplit("Line empty") from None
+    last_leaf = line.leaves[-1]
 
     bt = line.bracket_tracker
     try:
@@ -1176,9 +1265,11 @@ def delimiter_split(
     except ValueError:
         raise CannotSplit("No delimiters found") from None
 
-    if delimiter_priority == DOT_PRIORITY:
-        if bt.delimiter_count_with_priority(delimiter_priority) == 1:
-            raise CannotSplit("Splitting a single attribute from its owner looks wrong")
+    if (
+        delimiter_priority == DOT_PRIORITY
+        and bt.delimiter_count_with_priority(delimiter_priority) == 1
+    ):
+        raise CannotSplit("Splitting a single attribute from its owner looks wrong")
 
     current_line = Line(
         mode=line.mode, depth=line.depth, inside_brackets=line.inside_brackets
@@ -1199,40 +1290,45 @@ def append_to_line(leaf: Leaf) -> Iterator[Line]:
             )
             current_line.append(leaf)
 
+    def append_comments(leaf: Leaf) -> Iterator[Line]:
+        for comment_after in line.comments_after(leaf):
+            yield from append_to_line(comment_after)
+
     last_non_comment_leaf = _get_last_non_comment_leaf(line)
     for leaf_idx, leaf in enumerate(line.leaves):
         yield from append_to_line(leaf)
 
-        for comment_after in line.comments_after(leaf):
-            yield from append_to_line(comment_after)
+        previous_priority = leaf_idx > 0 and bt.delimiters.get(
+            id(line.leaves[leaf_idx - 1])
+        )
+        if (
+            previous_priority != delimiter_priority
+            or delimiter_priority in MIGRATE_COMMENT_DELIMITERS
+        ):
+            yield from append_comments(leaf)
 
         lowest_depth = min(lowest_depth, leaf.bracket_depth)
-        if leaf.bracket_depth == lowest_depth:
-            if is_vararg(leaf, within={syms.typedargslist}):
-                trailing_comma_safe = (
-                    trailing_comma_safe and Feature.TRAILING_COMMA_IN_DEF in features
-                )
-            elif is_vararg(leaf, within={syms.arglist, syms.argument}):
-                trailing_comma_safe = (
-                    trailing_comma_safe and Feature.TRAILING_COMMA_IN_CALL in features
-                )
+        if trailing_comma_safe and leaf.bracket_depth == lowest_depth:
+            trailing_comma_safe = _can_add_trailing_comma(leaf, features)
 
-        if (
-            Preview.add_trailing_comma_consistently in mode
-            and last_leaf.type == STANDALONE_COMMENT
-            and leaf_idx == last_non_comment_leaf
-        ):
+        if last_leaf.type == STANDALONE_COMMENT and leaf_idx == last_non_comment_leaf:
             current_line = _safe_add_trailing_comma(
                 trailing_comma_safe, delimiter_priority, current_line
             )
 
         leaf_priority = bt.delimiters.get(id(leaf))
         if leaf_priority == delimiter_priority:
-            yield current_line
+            if (
+                leaf_idx + 1 < len(line.leaves)
+                and delimiter_priority not in MIGRATE_COMMENT_DELIMITERS
+            ):
+                yield from append_comments(line.leaves[leaf_idx + 1])
 
+            yield current_line
             current_line = Line(
                 mode=line.mode, depth=line.depth, inside_brackets=line.inside_brackets
             )
+
     if current_line:
         current_line = _safe_add_trailing_comma(
             trailing_comma_safe, delimiter_priority, current_line
@@ -1276,7 +1372,7 @@ def append_to_line(leaf: Leaf) -> Iterator[Line]:
 
 
 def normalize_invisible_parens(  # noqa: C901
-    node: Node, parens_after: Set[str], *, mode: Mode, features: Collection[Feature]
+    node: Node, parens_after: set[str], *, mode: Mode, features: Collection[Feature]
 ) -> None:
     """Make existing optional parentheses invisible or create new ones.
 
@@ -1308,15 +1404,17 @@ def normalize_invisible_parens(  # noqa: C901
 
         # Fixes a bug where invisible parens are not properly wrapped around
         # case blocks.
-        if (
-            isinstance(child, Node)
-            and child.type == syms.case_block
-            and Preview.long_case_block_line_splitting in mode
-        ):
+        if isinstance(child, Node) and child.type == syms.case_block:
             normalize_invisible_parens(
                 child, parens_after={"case"}, mode=mode, features=features
             )
 
+        # Add parentheses around if guards in case blocks
+        if isinstance(child, Node) and child.type == syms.guard:
+            normalize_invisible_parens(
+                child, parens_after={"if"}, mode=mode, features=features
+            )
+
         # Add parentheses around long tuple unpacking in assignments.
         if (
             index == 0
@@ -1367,13 +1465,12 @@ def normalize_invisible_parens(  # noqa: C901
                 and child.next_sibling is not None
                 and child.next_sibling.type == token.COLON
                 and child.value == "case"
-                and Preview.long_case_block_line_splitting in mode
             ):
                 # A special patch for "case case:" scenario, the second occurrence
                 # of case will be not parsed as a Python keyword.
                 break
 
-            elif not (isinstance(child, Leaf) and is_multiline_string(child)):
+            elif not is_multiline_string(child):
                 wrap_in_parentheses(node, child, visible=False)
 
         comma_check = child.type == token.COMMA
@@ -1441,7 +1538,6 @@ def _maybe_wrap_cms_in_parens(
     """
     if (
         Feature.PARENTHESIZED_CONTEXT_MANAGERS not in features
-        or Preview.wrap_multiple_context_managers_in_parens not in mode
         or len(node.children) <= 2
         # If it's an atom, it's already wrapped in parens.
         or node.children[1].type == syms.atom
@@ -1532,6 +1628,12 @@ def maybe_make_parens_invisible_in_atom(
         node.type not in (syms.atom, syms.expr)
         or is_empty_tuple(node)
         or is_one_tuple(node)
+        or (is_tuple(node) and parent.type == syms.asexpr_test)
+        or (
+            is_tuple(node)
+            and parent.type == syms.with_stmt
+            and has_sibling_with_type(node, token.COMMA)
+        )
         or (is_yield(node) and parent.type != syms.expr_stmt)
         or (
             # This condition tries to prevent removing non-optional brackets
@@ -1541,6 +1643,8 @@ def maybe_make_parens_invisible_in_atom(
             and max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY
         )
         or is_tuple_containing_walrus(node)
+        or is_tuple_containing_star(node)
+        or is_generator(node)
     ):
         return False
 
@@ -1553,6 +1657,7 @@ def maybe_make_parens_invisible_in_atom(
             syms.except_clause,
             syms.funcdef,
             syms.with_stmt,
+            syms.testlist_gexp,
             syms.tname,
             # these ones aren't useful to end users, but they do please fuzzers
             syms.for_stmt,
@@ -1584,6 +1689,16 @@ def maybe_make_parens_invisible_in_atom(
             # it with the child in-between the invisible parens
             middle.replace(middle.children[1])
 
+            if middle.children[0].prefix.strip():
+                # Preserve comments before first paren
+                middle.children[1].prefix = (
+                    middle.children[0].prefix + middle.children[1].prefix
+                )
+
+            if middle.children[-1].prefix.strip():
+                # Preserve comments before last paren
+                last.prefix = middle.children[-1].prefix + last.prefix
+
         return False
 
     return True
@@ -1616,7 +1731,7 @@ def should_split_line(line: Line, opening_bracket: Leaf) -> bool:
     )
 
 
-def generate_trailers_to_omit(line: Line, line_length: int) -> Iterator[Set[LeafID]]:
+def generate_trailers_to_omit(line: Line, line_length: int) -> Iterator[set[LeafID]]:
     """Generate sets of closing bracket IDs that should be omitted in a RHS.
 
     Brackets can be omitted if the entire trailer up to and including
@@ -1627,15 +1742,15 @@ def generate_trailers_to_omit(line: Line, line_length: int) -> Iterator[Set[Leaf
     the one that needs to explode are omitted.
     """
 
-    omit: Set[LeafID] = set()
+    omit: set[LeafID] = set()
     if not line.magic_trailing_comma:
         yield omit
 
     length = 4 * line.depth
     opening_bracket: Optional[Leaf] = None
     closing_bracket: Optional[Leaf] = None
-    inner_brackets: Set[LeafID] = set()
-    for index, leaf, leaf_length in line.enumerate_with_length(reversed=True):
+    inner_brackets: set[LeafID] = set()
+    for index, leaf, leaf_length in line.enumerate_with_length(is_reversed=True):
         length += leaf_length
         if length > line_length:
             break
@@ -1699,10 +1814,10 @@ def run_transformer(
     features: Collection[Feature],
     *,
     line_str: str = "",
-) -> List[Line]:
+) -> list[Line]:
     if not line_str:
         line_str = line_to_string(line)
-    result: List[Line] = []
+    result: list[Line] = []
     for transformed_line in transform(line, features, mode):
         if str(transformed_line).strip("\n") == line_str:
             raise CannotTransform("Line transformer returned an unchanged result")

src/black/lines.py

@@ -1,18 +1,8 @@
 import itertools
 import math
+from collections.abc import Callable, Iterator, Sequence
 from dataclasses import dataclass, field
-from typing import (
-    Callable,
-    Dict,
-    Iterator,
-    List,
-    Optional,
-    Sequence,
-    Tuple,
-    TypeVar,
-    Union,
-    cast,
-)
+from typing import Optional, TypeVar, Union, cast
 
 from black.brackets import COMMA_PRIORITY, DOT_PRIORITY, BracketTracker
 from black.mode import Mode, Preview
@@ -24,7 +14,6 @@
     TEST_DESCENDANTS,
     child_towards,
     is_docstring,
-    is_funcdef,
     is_import,
     is_multiline_string,
     is_one_sequence_between,
@@ -53,9 +42,9 @@ class Line:
 
     mode: Mode = field(repr=False)
     depth: int = 0
-    leaves: List[Leaf] = field(default_factory=list)
+    leaves: list[Leaf] = field(default_factory=list)
     # keys ordered like `leaves`
-    comments: Dict[LeafID, List[Leaf]] = field(default_factory=dict)
+    comments: dict[LeafID, list[Leaf]] = field(default_factory=dict)
     bracket_tracker: BracketTracker = field(default_factory=BracketTracker)
     inside_brackets: bool = False
     should_split_rhs: bool = False
@@ -73,7 +62,12 @@ def append(
 
         Inline comments are put aside.
         """
-        has_value = leaf.type in BRACKETS or bool(leaf.value.strip())
+        has_value = (
+            leaf.type in BRACKETS
+            # empty fstring-middles must not be truncated
+            or leaf.type == token.FSTRING_MIDDLE
+            or bool(leaf.value.strip())
+        )
         if not has_value:
             return
 
@@ -92,7 +86,7 @@ def append(
             if self.mode.magic_trailing_comma:
                 if self.has_magic_trailing_comma(leaf):
                     self.magic_trailing_comma = leaf
-            elif self.has_magic_trailing_comma(leaf, ensure_removable=True):
+            elif self.has_magic_trailing_comma(leaf):
                 self.remove_trailing_comma()
         if not self.append_comment(leaf):
             self.leaves.append(leaf)
@@ -196,19 +190,22 @@ def is_class_paren_empty(self) -> bool:
         )
 
     @property
-    def is_triple_quoted_string(self) -> bool:
+    def _is_triple_quoted_string(self) -> bool:
         """Is the line a triple quoted string?"""
         if not self or self.leaves[0].type != token.STRING:
             return False
         value = self.leaves[0].value
         if value.startswith(('"""', "'''")):
             return True
-        if Preview.accept_raw_docstrings in self.mode and value.startswith(
-            ("r'''", 'r"""', "R'''", 'R"""')
-        ):
+        if value.startswith(("r'''", 'r"""', "R'''", 'R"""')):
             return True
         return False
 
+    @property
+    def is_docstring(self) -> bool:
+        """Is the line a docstring?"""
+        return bool(self) and is_docstring(self.leaves[0])
+
     @property
     def is_chained_assignment(self) -> bool:
         """Is the line a chained assignment"""
@@ -336,16 +333,11 @@ def contains_unsplittable_type_ignore(self) -> bool:
     def contains_multiline_strings(self) -> bool:
         return any(is_multiline_string(leaf) for leaf in self.leaves)
 
-    def has_magic_trailing_comma(
-        self, closing: Leaf, ensure_removable: bool = False
-    ) -> bool:
+    def has_magic_trailing_comma(self, closing: Leaf) -> bool:
         """Return True if we have a magic trailing comma, that is when:
         - there's a trailing comma here
+        - it's not from single-element square bracket indexing
         - it's not a one-tuple
-        - it's not a single-element subscript
-        Additionally, if ensure_removable:
-        - it's not from square bracket indexing
-        (specifically, single-element square bracket indexing)
         """
         if not (
             closing.type in CLOSING_BRACKETS
@@ -369,6 +361,8 @@ def has_magic_trailing_comma(
                     brackets=(token.LSQB, token.RSQB),
                 )
             ):
+                assert closing.prev_sibling is not None
+                assert closing.prev_sibling.type == syms.subscriptlist
                 return False
 
             return True
@@ -420,7 +414,7 @@ def append_comment(self, comment: Leaf) -> bool:
         self.comments.setdefault(id(last_leaf), []).append(comment)
         return True
 
-    def comments_after(self, leaf: Leaf) -> List[Leaf]:
+    def comments_after(self, leaf: Leaf) -> list[Leaf]:
         """Generate comments that should appear directly after `leaf`."""
         return self.comments.get(id(leaf), [])
 
@@ -446,20 +440,21 @@ def is_complex_subscript(self, leaf: Leaf) -> bool:
 
             if subscript_start.type == syms.subscriptlist:
                 subscript_start = child_towards(subscript_start, leaf)
+
         return subscript_start is not None and any(
             n.type in TEST_DESCENDANTS for n in subscript_start.pre_order()
         )
 
     def enumerate_with_length(
-        self, reversed: bool = False
-    ) -> Iterator[Tuple[Index, Leaf, int]]:
+        self, is_reversed: bool = False
+    ) -> Iterator[tuple[Index, Leaf, int]]:
         """Return an enumeration of leaves with their length.
 
         Stops prematurely on multiline strings and standalone comments.
         """
         op = cast(
-            Callable[[Sequence[Leaf]], Iterator[Tuple[Index, Leaf]]],
-            enumerate_reversed if reversed else enumerate,
+            Callable[[Sequence[Leaf]], Iterator[tuple[Index, Leaf]]],
+            enumerate_reversed if is_reversed else enumerate,
         )
         for index, leaf in op(self.leaves):
             length = len(leaf.prefix) + len(leaf.value)
@@ -524,11 +519,11 @@ class LinesBlock:
     previous_block: Optional["LinesBlock"]
     original_line: Line
     before: int = 0
-    content_lines: List[str] = field(default_factory=list)
+    content_lines: list[str] = field(default_factory=list)
     after: int = 0
     form_feed: bool = False
 
-    def all_lines(self) -> List[str]:
+    def all_lines(self) -> list[str]:
         empty_line = str(Line(mode=self.mode))
         prefix = make_simple_prefix(self.before, self.form_feed, empty_line)
         return [prefix] + self.content_lines + [empty_line * self.after]
@@ -547,7 +542,7 @@ class EmptyLineTracker:
     mode: Mode
     previous_line: Optional[Line] = None
     previous_block: Optional[LinesBlock] = None
-    previous_defs: List[Line] = field(default_factory=list)
+    previous_defs: list[Line] = field(default_factory=list)
     semantic_leading_comment: Optional[LinesBlock] = None
 
     def maybe_empty_lines(self, current_line: Line) -> LinesBlock:
@@ -557,26 +552,19 @@ def maybe_empty_lines(self, current_line: Line) -> LinesBlock:
         lines (two on module-level).
         """
         form_feed = (
-            Preview.allow_form_feeds in self.mode
-            and current_line.depth == 0
+            current_line.depth == 0
             and bool(current_line.leaves)
             and "\f\n" in current_line.leaves[0].prefix
         )
         before, after = self._maybe_empty_lines(current_line)
         previous_after = self.previous_block.after if self.previous_block else 0
-        before = (
-            # Black should not insert empty lines at the beginning
-            # of the file
-            0
-            if self.previous_line is None
-            else before - previous_after
-        )
+        before = max(0, before - previous_after)
         if (
-            Preview.module_docstring_newlines in current_line.mode
-            and self.previous_block
+            # Always have one empty line after a module docstring
+            self.previous_block
             and self.previous_block.previous_block is None
             and len(self.previous_block.original_line.leaves) == 1
-            and self.previous_block.original_line.is_triple_quoted_string
+            and self.previous_block.original_line.is_docstring
             and not (current_line.is_class or current_line.is_def)
         ):
             before = 1
@@ -607,10 +595,11 @@ def maybe_empty_lines(self, current_line: Line) -> LinesBlock:
         self.previous_block = block
         return block
 
-    def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
+    def _maybe_empty_lines(self, current_line: Line) -> tuple[int, int]:  # noqa: C901
         max_allowed = 1
         if current_line.depth == 0:
             max_allowed = 1 if self.mode.is_pyi else 2
+
         if current_line.leaves:
             # Consume the first leaf's extra newlines.
             first_leaf = current_line.leaves[0]
@@ -623,22 +612,31 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
         user_had_newline = bool(before)
         depth = current_line.depth
 
+        # Mutate self.previous_defs, remainder of this function should be pure
         previous_def = None
         while self.previous_defs and self.previous_defs[-1].depth >= depth:
             previous_def = self.previous_defs.pop()
+        if current_line.is_def or current_line.is_class:
+            self.previous_defs.append(current_line)
+
+        if self.previous_line is None:
+            # Don't insert empty lines before the first line in the file.
+            return 0, 0
+
+        if current_line.is_docstring:
+            if self.previous_line.is_class:
+                return 0, 1
+            if self.previous_line.opens_block and self.previous_line.is_def:
+                return 0, 0
 
         if previous_def is not None:
             assert self.previous_line is not None
             if self.mode.is_pyi:
-                if depth and not current_line.is_def and self.previous_line.is_def:
+                if previous_def.is_class and not previous_def.is_stub_class:
+                    before = 1
+                elif depth and not current_line.is_def and self.previous_line.is_def:
                     # Empty lines between attributes and methods should be preserved.
                     before = 1 if user_had_newline else 0
-                elif (
-                    Preview.blank_line_after_nested_stub_class in self.mode
-                    and previous_def.is_class
-                    and not previous_def.is_stub_class
-                ):
-                    before = 1
                 elif depth:
                     before = 0
                 else:
@@ -672,66 +670,41 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
             )
 
         if (
-            self.previous_line
-            and self.previous_line.is_import
+            self.previous_line.is_import
+            and self.previous_line.depth == 0
+            and current_line.depth == 0
+            and not current_line.is_import
+            and Preview.always_one_newline_after_import in self.mode
+        ):
+            return 1, 0
+
+        if (
+            self.previous_line.is_import
             and not current_line.is_import
             and not current_line.is_fmt_pass_converted(first_leaf_matches=is_import)
             and depth == self.previous_line.depth
         ):
             return (before or 1), 0
 
-        if (
-            self.previous_line
-            and self.previous_line.is_class
-            and current_line.is_triple_quoted_string
-        ):
-            if Preview.no_blank_line_before_class_docstring in current_line.mode:
-                return 0, 1
-            return before, 1
-
-        # In preview mode, always allow blank lines, except right before a function
-        # docstring
-        is_empty_first_line_ok = (
-            Preview.allow_empty_first_line_in_block in current_line.mode
-            and (
-                not is_docstring(current_line.leaves[0])
-                or (
-                    self.previous_line
-                    and self.previous_line.leaves[0]
-                    and self.previous_line.leaves[0].parent
-                    and not is_funcdef(self.previous_line.leaves[0].parent)
-                )
-            )
-        )
-
-        if (
-            self.previous_line
-            and self.previous_line.opens_block
-            and not is_empty_first_line_ok
-        ):
-            return 0, 0
         return before, 0
 
     def _maybe_empty_lines_for_class_or_def(  # noqa: C901
         self, current_line: Line, before: int, user_had_newline: bool
-    ) -> Tuple[int, int]:
-        if not current_line.is_decorator:
-            self.previous_defs.append(current_line)
-        if self.previous_line is None:
-            # Don't insert empty lines before the first line in the file.
-            return 0, 0
+    ) -> tuple[int, int]:
+        assert self.previous_line is not None
 
         if self.previous_line.is_decorator:
             if self.mode.is_pyi and current_line.is_stub_class:
                 # Insert an empty line after a decorated stub class
                 return 0, 1
-
             return 0, 0
 
         if self.previous_line.depth < current_line.depth and (
             self.previous_line.is_class or self.previous_line.is_def
         ):
-            return 0, 0
+            if self.mode.is_pyi:
+                return 0, 0
+            return 1 if user_had_newline else 0, 0
 
         comment_to_add_newlines: Optional[LinesBlock] = None
         if (
@@ -762,16 +735,10 @@ def _maybe_empty_lines_for_class_or_def(  # noqa: C901
                     newlines = 0
                 else:
                     newlines = 1
-            # Remove case `self.previous_line.depth > current_line.depth` below when
-            # this becomes stable.
-            #
             # Don't inspect the previous line if it's part of the body of the previous
             # statement in the same level, we always want a blank line if there's
             # something with a body preceding.
-            elif (
-                Preview.blank_line_between_nested_and_def_stub_file in current_line.mode
-                and self.previous_line.depth > current_line.depth
-            ):
+            elif self.previous_line.depth > current_line.depth:
                 newlines = 1
             elif (
                 current_line.is_def or current_line.is_decorator
@@ -784,19 +751,13 @@ def _maybe_empty_lines_for_class_or_def(  # noqa: C901
                     # Blank line between a block of functions (maybe with preceding
                     # decorators) and a block of non-functions
                     newlines = 1
-            elif self.previous_line.depth > current_line.depth:
-                newlines = 1
             else:
                 newlines = 0
         else:
             newlines = 1 if current_line.depth else 2
             # If a user has left no space after a dummy implementation, don't insert
             # new lines. This is useful for instance for @overload or Protocols.
-            if (
-                Preview.dummy_implementations in self.mode
-                and self.previous_line.is_stub_def
-                and not user_had_newline
-            ):
+            if self.previous_line.is_stub_def and not user_had_newline:
                 newlines = 0
         if comment_to_add_newlines is not None:
             previous_block = comment_to_add_newlines.previous_block
@@ -808,7 +769,7 @@ def _maybe_empty_lines_for_class_or_def(  # noqa: C901
         return newlines, 0
 
 
-def enumerate_reversed(sequence: Sequence[T]) -> Iterator[Tuple[Index, T]]:
+def enumerate_reversed(sequence: Sequence[T]) -> Iterator[tuple[Index, T]]:
     """Like `reversed(enumerate(sequence))` if that were possible."""
     index = len(sequence) - 1
     for element in reversed(sequence):
@@ -817,7 +778,7 @@ def enumerate_reversed(sequence: Sequence[T]) -> Iterator[Tuple[Index, T]]:
 
 
 def append_leaves(
-    new_line: Line, old_line: Line, leaves: List[Leaf], preformatted: bool = False
+    new_line: Line, old_line: Line, leaves: list[Leaf], preformatted: bool = False
 ) -> None:
     """
     Append leaves (taken from @old_line) to @new_line, making sure to fix the
@@ -851,11 +812,9 @@ def is_line_short_enough(  # noqa: C901
     if not line_str:
         line_str = line_to_string(line)
 
-    width = str_width if Preview.respect_east_asian_width in mode else len
-
     if Preview.multiline_string_handling not in mode:
         return (
-            width(line_str) <= mode.line_length
+            str_width(line_str) <= mode.line_length
             and "\n" not in line_str  # multiline strings
             and not line.contains_standalone_comments()
         )
@@ -864,10 +823,10 @@ def is_line_short_enough(  # noqa: C901
         return False
     if "\n" not in line_str:
         # No multiline strings (MLS) present
-        return width(line_str) <= mode.line_length
+        return str_width(line_str) <= mode.line_length
 
     first, *_, last = line_str.split("\n")
-    if width(first) > mode.line_length or width(last) > mode.line_length:
+    if str_width(first) > mode.line_length or str_width(last) > mode.line_length:
         return False
 
     # Traverse the AST to examine the context of the multiline string (MLS),
@@ -876,10 +835,10 @@ def is_line_short_enough(  # noqa: C901
     # Depth (which is based on the existing bracket_depth concept)
     # is needed to determine nesting level of the MLS.
     # Includes special case for trailing commas.
-    commas: List[int] = []  # tracks number of commas per depth level
+    commas: list[int] = []  # tracks number of commas per depth level
     multiline_string: Optional[Leaf] = None
     # store the leaves that contain parts of the MLS
-    multiline_string_contexts: List[LN] = []
+    multiline_string_contexts: list[LN] = []
 
     max_level_to_update: Union[int, float] = math.inf  # track the depth of the MLS
     for i, leaf in enumerate(line.leaves):
@@ -901,11 +860,13 @@ def is_line_short_enough(  # noqa: C901
                     return False
 
         if leaf.bracket_depth <= max_level_to_update and leaf.type == token.COMMA:
-            # Ignore non-nested trailing comma
+            # Inside brackets, ignore trailing comma
             # directly after MLS/MLS-containing expression
-            ignore_ctxs: List[Optional[LN]] = [None]
+            ignore_ctxs: list[Optional[LN]] = [None]
             ignore_ctxs += multiline_string_contexts
-            if not (leaf.prev_sibling in ignore_ctxs and i == len(line.leaves) - 1):
+            if (line.inside_brackets or leaf.bracket_depth > 0) and (
+                i != len(line.leaves) - 1 or leaf.prev_sibling not in ignore_ctxs
+            ):
                 commas[leaf.bracket_depth] += 1
         if max_level_to_update != math.inf:
             max_level_to_update = min(max_level_to_update, leaf.bracket_depth)
@@ -1007,11 +968,7 @@ def can_omit_invisible_parens(
         return False
 
     if delimiter_count == 1:
-        if (
-            Preview.wrap_multiple_context_managers_in_parens in line.mode
-            and max_priority == COMMA_PRIORITY
-            and rhs.head.is_with_or_async_with_stmt
-        ):
+        if max_priority == COMMA_PRIORITY and rhs.head.is_with_or_async_with_stmt:
             # For two context manager with statements, the optional parentheses read
             # better. In this case, `rhs.body` is the context managers part of
             # the with statement. `rhs.head` is the `with (` part on the previous

src/black/mode.py

@@ -8,8 +8,7 @@
 from enum import Enum, auto
 from hashlib import sha256
 from operator import attrgetter
-from typing import Dict, Final, Set
-from warnings import warn
+from typing import Final
 
 from black.const import DEFAULT_LINE_LENGTH
 
@@ -25,6 +24,11 @@ class TargetVersion(Enum):
     PY310 = 10
     PY311 = 11
     PY312 = 12
+    PY313 = 13
+
+    def pretty(self) -> str:
+        assert self.name[:2] == "PY"
+        return f"Python {self.name[2]}.{self.name[3:]}"
 
 
 class Feature(Enum):
@@ -47,6 +51,8 @@ class Feature(Enum):
     DEBUG_F_STRINGS = 16
     PARENTHESIZED_CONTEXT_MANAGERS = 17
     TYPE_PARAMS = 18
+    FSTRING_PARSING = 19
+    TYPE_PARAM_DEFAULTS = 20
     FORCE_OPTIONAL_PARENTHESES = 50
 
     # __future__ flags
@@ -58,7 +64,7 @@ class Feature(Enum):
 }
 
 
-VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
+VERSION_TO_FEATURES: dict[TargetVersion, set[Feature]] = {
     TargetVersion.PY33: {Feature.ASYNC_IDENTIFIERS},
     TargetVersion.PY34: {Feature.ASYNC_IDENTIFIERS},
     TargetVersion.PY35: {Feature.TRAILING_COMMA_IN_CALL, Feature.ASYNC_IDENTIFIERS},
@@ -157,82 +163,93 @@ class Feature(Enum):
         Feature.EXCEPT_STAR,
         Feature.VARIADIC_GENERICS,
         Feature.TYPE_PARAMS,
+        Feature.FSTRING_PARSING,
+    },
+    TargetVersion.PY313: {
+        Feature.F_STRINGS,
+        Feature.DEBUG_F_STRINGS,
+        Feature.NUMERIC_UNDERSCORES,
+        Feature.TRAILING_COMMA_IN_CALL,
+        Feature.TRAILING_COMMA_IN_DEF,
+        Feature.ASYNC_KEYWORDS,
+        Feature.FUTURE_ANNOTATIONS,
+        Feature.ASSIGNMENT_EXPRESSIONS,
+        Feature.RELAXED_DECORATORS,
+        Feature.POS_ONLY_ARGUMENTS,
+        Feature.UNPACKING_ON_FLOW,
+        Feature.ANN_ASSIGN_EXTENDED_RHS,
+        Feature.PARENTHESIZED_CONTEXT_MANAGERS,
+        Feature.PATTERN_MATCHING,
+        Feature.EXCEPT_STAR,
+        Feature.VARIADIC_GENERICS,
+        Feature.TYPE_PARAMS,
+        Feature.FSTRING_PARSING,
+        Feature.TYPE_PARAM_DEFAULTS,
     },
 }
 
 
-def supports_feature(target_versions: Set[TargetVersion], feature: Feature) -> bool:
+def supports_feature(target_versions: set[TargetVersion], feature: Feature) -> bool:
     return all(feature in VERSION_TO_FEATURES[version] for version in target_versions)
 
 
 class Preview(Enum):
     """Individual preview style features."""
 
-    add_trailing_comma_consistently = auto()
-    blank_line_after_nested_stub_class = auto()
-    blank_line_between_nested_and_def_stub_file = auto()
-    hex_codes_in_unicode_sequences = auto()
-    improved_async_statements_handling = auto()
-    multiline_string_handling = auto()
-    no_blank_line_before_class_docstring = auto()
-    prefer_splitting_right_hand_side_of_assignments = auto()
     # NOTE: string_processing requires wrap_long_dict_values_in_parens
     # for https://github.com/psf/black/issues/3117 to be fixed.
     string_processing = auto()
-    parenthesize_conditional_expressions = auto()
-    parenthesize_long_type_hints = auto()
-    respect_magic_trailing_comma_in_return_type = auto()
-    skip_magic_trailing_comma_in_subscript = auto()
-    wrap_long_dict_values_in_parens = auto()
-    wrap_multiple_context_managers_in_parens = auto()
-    dummy_implementations = auto()
-    walrus_subscript = auto()
-    module_docstring_newlines = auto()
-    accept_raw_docstrings = auto()
-    fix_power_op_line_length = auto()
     hug_parens_with_braces_and_square_brackets = auto()
-    allow_empty_first_line_in_block = auto()
-    single_line_format_skip_with_multiple_comments = auto()
-    long_case_block_line_splitting = auto()
-    allow_form_feeds = auto()
-    respect_east_asian_width = auto()
+    wrap_long_dict_values_in_parens = auto()
+    multiline_string_handling = auto()
+    always_one_newline_after_import = auto()
+    fix_fmt_skip_in_one_liners = auto()
+
+
+UNSTABLE_FEATURES: set[Preview] = {
+    # Many issues, see summary in https://github.com/psf/black/issues/4042
+    Preview.string_processing,
+    # See issue #4159
+    Preview.multiline_string_handling,
+    # See issue #4036 (crash), #4098, #4099 (proposed tweaks)
+    Preview.hug_parens_with_braces_and_square_brackets,
+}
 
 
 class Deprecated(UserWarning):
     """Visible deprecation warning."""
 
 
+_MAX_CACHE_KEY_PART_LENGTH: Final = 32
+
+
 @dataclass
 class Mode:
-    target_versions: Set[TargetVersion] = field(default_factory=set)
+    target_versions: set[TargetVersion] = field(default_factory=set)
     line_length: int = DEFAULT_LINE_LENGTH
     string_normalization: bool = True
     is_pyi: bool = False
     is_ipynb: bool = False
     skip_source_first_line: bool = False
     magic_trailing_comma: bool = True
-    experimental_string_processing: bool = False
-    python_cell_magics: Set[str] = field(default_factory=set)
+    python_cell_magics: set[str] = field(default_factory=set)
     preview: bool = False
-
-    def __post_init__(self) -> None:
-        if self.experimental_string_processing:
-            warn(
-                "`experimental string processing` has been included in `preview`"
-                " and deprecated. Use `preview` instead.",
-                Deprecated,
-            )
+    unstable: bool = False
+    enabled_features: set[Preview] = field(default_factory=set)
 
     def __contains__(self, feature: Preview) -> bool:
         """
         Provide `Preview.FEATURE in Mode` syntax that mirrors the ``preview`` flag.
 
-        The argument is not checked and features are not differentiated.
-        They only exist to make development easier by clarifying intent.
+        In unstable mode, all features are enabled. In preview mode, all features
+        except those in UNSTABLE_FEATURES are enabled. Any features in
+        `self.enabled_features` are also enabled.
         """
-        if feature is Preview.string_processing:
-            return self.preview or self.experimental_string_processing
-        return self.preview
+        if self.unstable:
+            return True
+        if feature in self.enabled_features:
+            return True
+        return self.preview and feature not in UNSTABLE_FEATURES
 
     def get_cache_key(self) -> str:
         if self.target_versions:
@@ -242,6 +259,19 @@ def get_cache_key(self) -> str:
             )
         else:
             version_str = "-"
+        if len(version_str) > _MAX_CACHE_KEY_PART_LENGTH:
+            version_str = sha256(version_str.encode()).hexdigest()[
+                :_MAX_CACHE_KEY_PART_LENGTH
+            ]
+        features_and_magics = (
+            ",".join(sorted(f.name for f in self.enabled_features))
+            + "@"
+            + ",".join(sorted(self.python_cell_magics))
+        )
+        if len(features_and_magics) > _MAX_CACHE_KEY_PART_LENGTH:
+            features_and_magics = sha256(features_and_magics.encode()).hexdigest()[
+                :_MAX_CACHE_KEY_PART_LENGTH
+            ]
         parts = [
             version_str,
             str(self.line_length),
@@ -250,8 +280,8 @@ def get_cache_key(self) -> str:
             str(int(self.is_ipynb)),
             str(int(self.skip_source_first_line)),
             str(int(self.magic_trailing_comma)),
-            str(int(self.experimental_string_processing)),
             str(int(self.preview)),
-            sha256((",".join(sorted(self.python_cell_magics))).encode()).hexdigest(),
+            str(int(self.unstable)),
+            features_and_magics,
         ]
         return ".".join(parts)

src/black/nodes.py

@@ -3,7 +3,8 @@
 """
 
 import sys
-from typing import Final, Generic, Iterator, List, Optional, Set, Tuple, TypeVar, Union
+from collections.abc import Iterator
+from typing import Final, Generic, Literal, Optional, TypeVar, Union
 
 if sys.version_info >= (3, 10):
     from typing import TypeGuard
@@ -13,7 +14,7 @@
 from mypy_extensions import mypyc_attr
 
 from black.cache import CACHE_DIR
-from black.mode import Mode, Preview
+from black.mode import Mode
 from black.strings import get_string_prefix, has_triple_quotes
 from blib2to3 import pygram
 from blib2to3.pgen2 import token
@@ -104,6 +105,7 @@
     syms.trailer,
     syms.term,
     syms.power,
+    syms.namedexpr_test,
 }
 TYPED_NAMES: Final = {syms.tname, syms.tname_star}
 ASSIGNMENTS: Final = {
@@ -121,6 +123,7 @@
     ">>=",
     "**=",
     "//=",
+    ":",
 }
 
 IMPLICIT_TUPLE: Final = {syms.testlist, syms.testlist_star_expr, syms.exprlist}
@@ -132,7 +135,13 @@
 OPENING_BRACKETS: Final = set(BRACKET.keys())
 CLOSING_BRACKETS: Final = set(BRACKET.values())
 BRACKETS: Final = OPENING_BRACKETS | CLOSING_BRACKETS
-ALWAYS_NO_SPACE: Final = CLOSING_BRACKETS | {token.COMMA, STANDALONE_COMMENT}
+ALWAYS_NO_SPACE: Final = CLOSING_BRACKETS | {
+    token.COMMA,
+    STANDALONE_COMMENT,
+    token.FSTRING_MIDDLE,
+    token.FSTRING_END,
+    token.BANG,
+}
 
 RARROW = 55
 
@@ -198,6 +207,9 @@ def whitespace(leaf: Leaf, *, complex_subscript: bool, mode: Mode) -> str:  # no
     }:
         return NO
 
+    if t == token.LBRACE and p.type == syms.fstring_replacement_field:
+        return NO
+
     prev = leaf.prev_sibling
     if not prev:
         prevp = preceding_leaf(p)
@@ -232,9 +244,9 @@ def whitespace(leaf: Leaf, *, complex_subscript: bool, mode: Mode) -> str:  # no
         elif (
             prevp.type == token.STAR
             and parent_type(prevp) == syms.star_expr
-            and parent_type(prevp.parent) == syms.subscriptlist
+            and parent_type(prevp.parent) in (syms.subscriptlist, syms.tname_star)
         ):
-            # No space between typevar tuples.
+            # No space between typevar tuples or unpacking them.
             return NO
 
         elif prevp.type in VARARGS_SPECIALS:
@@ -259,6 +271,9 @@ def whitespace(leaf: Leaf, *, complex_subscript: bool, mode: Mode) -> str:  # no
     elif prev.type in OPENING_BRACKETS:
         return NO
 
+    elif prev.type == token.BANG:
+        return NO
+
     if p.type in {syms.parameters, syms.arglist}:
         # untyped function signatures or calls
         if not prev or prev.type != token.COMMA:
@@ -346,9 +361,7 @@ def whitespace(leaf: Leaf, *, complex_subscript: bool, mode: Mode) -> str:  # no
 
             return NO
 
-        elif Preview.walrus_subscript in mode and (
-            t == token.COLONEQUAL or prev.type == token.COLONEQUAL
-        ):
+        elif t == token.COLONEQUAL or prev.type == token.COLONEQUAL:
             return SPACE
 
         elif not complex_subscript:
@@ -382,6 +395,7 @@ def whitespace(leaf: Leaf, *, complex_subscript: bool, mode: Mode) -> str:  # no
             elif prevp.type == token.EQUAL and prevp_parent.type == syms.argument:
                 return NO
 
+        # TODO: add fstring here?
         elif t in {token.NAME, token.NUMBER, token.STRING}:
             return NO
 
@@ -432,7 +446,7 @@ def preceding_leaf(node: Optional[LN]) -> Optional[Leaf]:
     return None
 
 
-def prev_siblings_are(node: Optional[LN], tokens: List[Optional[NodeType]]) -> bool:
+def prev_siblings_are(node: Optional[LN], tokens: list[Optional[NodeType]]) -> bool:
     """Return if the `node` and its previous siblings match types against the provided
     list of tokens; the provided `node`has its type matched against the last element in
     the list.  `None` can be used as the first element to declare that the start of the
@@ -531,21 +545,31 @@ def is_arith_like(node: LN) -> bool:
     }
 
 
-def is_docstring(leaf: Leaf) -> bool:
-    if leaf.type != token.STRING:
-        return False
+def is_docstring(node: NL) -> bool:
+    if isinstance(node, Leaf):
+        if node.type != token.STRING:
+            return False
 
-    prefix = get_string_prefix(leaf.value)
-    if set(prefix).intersection("bBfF"):
-        return False
+        prefix = get_string_prefix(node.value)
+        if set(prefix).intersection("bBfF"):
+            return False
+
+    if (
+        node.parent
+        and node.parent.type == syms.simple_stmt
+        and not node.parent.prev_sibling
+        and node.parent.parent
+        and node.parent.parent.type == syms.file_input
+    ):
+        return True
 
     if prev_siblings_are(
-        leaf.parent, [None, token.NEWLINE, token.INDENT, syms.simple_stmt]
+        node.parent, [None, token.NEWLINE, token.INDENT, syms.simple_stmt]
     ):
         return True
 
     # Multiline docstring on the same line as the `def`.
-    if prev_siblings_are(leaf.parent, [syms.parameters, token.COLON, syms.simple_stmt]):
+    if prev_siblings_are(node.parent, [syms.parameters, token.COLON, syms.simple_stmt]):
         # `syms.parameters` is only used in funcdefs and async_funcdefs in the Python
         # grammar. We're safe to return True without further checks.
         return True
@@ -579,6 +603,17 @@ def is_one_tuple(node: LN) -> bool:
     )
 
 
+def is_tuple(node: LN) -> bool:
+    """Return True if `node` holds a tuple."""
+    if node.type != syms.atom:
+        return False
+    gexp = unwrap_singleton_parenthesis(node)
+    if gexp is None or gexp.type != syms.testlist_gexp:
+        return False
+
+    return True
+
+
 def is_tuple_containing_walrus(node: LN) -> bool:
     """Return True if `node` holds a tuple that contains a walrus operator."""
     if node.type != syms.atom:
@@ -590,11 +625,33 @@ def is_tuple_containing_walrus(node: LN) -> bool:
     return any(child.type == syms.namedexpr_test for child in gexp.children)
 
 
+def is_tuple_containing_star(node: LN) -> bool:
+    """Return True if `node` holds a tuple that contains a star operator."""
+    if node.type != syms.atom:
+        return False
+    gexp = unwrap_singleton_parenthesis(node)
+    if gexp is None or gexp.type != syms.testlist_gexp:
+        return False
+
+    return any(child.type == syms.star_expr for child in gexp.children)
+
+
+def is_generator(node: LN) -> bool:
+    """Return True if `node` holds a generator."""
+    if node.type != syms.atom:
+        return False
+    gexp = unwrap_singleton_parenthesis(node)
+    if gexp is None or gexp.type != syms.testlist_gexp:
+        return False
+
+    return any(child.type == syms.old_comp_for for child in gexp.children)
+
+
 def is_one_sequence_between(
     opening: Leaf,
     closing: Leaf,
-    leaves: List[Leaf],
-    brackets: Tuple[int, int] = (token.LPAR, token.RPAR),
+    leaves: list[Leaf],
+    brackets: tuple[int, int] = (token.LPAR, token.RPAR),
 ) -> bool:
     """Return True if content between `opening` and `closing` is a one-sequence."""
     if (opening.type, closing.type) != brackets:
@@ -704,7 +761,7 @@ def is_yield(node: LN) -> bool:
     return False
 
 
-def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
+def is_vararg(leaf: Leaf, within: set[NodeType]) -> bool:
     """Return True if `leaf` is a star or double star in a vararg or kwarg.
 
     If `within` includes VARARGS_PARENTS, this applies to function signatures.
@@ -727,26 +784,45 @@ def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
     return p.type in within
 
 
-def is_multiline_string(leaf: Leaf) -> bool:
+def is_fstring(node: Node) -> bool:
+    """Return True if the node is an f-string"""
+    return node.type == syms.fstring
+
+
+def fstring_to_string(node: Node) -> Leaf:
+    """Converts an fstring node back to a string node."""
+    string_without_prefix = str(node)[len(node.prefix) :]
+    string_leaf = Leaf(token.STRING, string_without_prefix, prefix=node.prefix)
+    string_leaf.lineno = node.get_lineno() or 0
+    return string_leaf
+
+
+def is_multiline_string(node: LN) -> bool:
     """Return True if `leaf` is a multiline string that actually spans many lines."""
+    if isinstance(node, Node) and is_fstring(node):
+        leaf = fstring_to_string(node)
+    elif isinstance(node, Leaf):
+        leaf = node
+    else:
+        return False
+
     return has_triple_quotes(leaf.value) and "\n" in leaf.value
 
 
-def is_funcdef(node: Node) -> bool:
-    return node.type == syms.funcdef
+def is_parent_function_or_class(node: Node) -> bool:
+    assert node.type in {syms.suite, syms.simple_stmt}
+    assert node.parent is not None
+    # Note this works for suites / simple_stmts in async def as well
+    return node.parent.type in {syms.funcdef, syms.classdef}
 
 
 def is_function_or_class(node: Node) -> bool:
     return node.type in {syms.funcdef, syms.classdef, syms.async_funcdef}
 
 
-def is_stub_suite(node: Node, mode: Mode) -> bool:
+def is_stub_suite(node: Node) -> bool:
     """Return True if `node` is a suite with a stub body."""
-    if (
-        node.parent is not None
-        and Preview.dummy_implementations in mode
-        and not is_function_or_class(node.parent)
-    ):
+    if node.parent is not None and not is_parent_function_or_class(node):
         return False
 
     # If there is a comment, we want to keep it.
@@ -934,24 +1010,26 @@ def is_rpar_token(nl: NL) -> TypeGuard[Leaf]:
     return nl.type == token.RPAR
 
 
-def is_string_token(nl: NL) -> TypeGuard[Leaf]:
-    return nl.type == token.STRING
-
-
 def is_number_token(nl: NL) -> TypeGuard[Leaf]:
     return nl.type == token.NUMBER
 
 
-def is_part_of_annotation(leaf: Leaf) -> bool:
-    """Returns whether this leaf is part of type annotations."""
+def get_annotation_type(leaf: Leaf) -> Literal["return", "param", None]:
+    """Returns the type of annotation this leaf is part of, if any."""
     ancestor = leaf.parent
     while ancestor is not None:
         if ancestor.prev_sibling and ancestor.prev_sibling.type == token.RARROW:
-            return True
+            return "return"
         if ancestor.parent and ancestor.parent.type == syms.tname:
-            return True
+            return "param"
         ancestor = ancestor.parent
-    return False
+    return None
+
+
+def is_part_of_annotation(leaf: Leaf) -> bool:
+    """Returns whether this leaf is part of a type annotation."""
+    assert leaf.parent is not None
+    return get_annotation_type(leaf) is not None
 
 
 def first_leaf(node: LN) -> Optional[Leaf]:
@@ -980,3 +1058,21 @@ def furthest_ancestor_with_last_leaf(leaf: Leaf) -> LN:
     while node.parent and node.parent.children and node is node.parent.children[-1]:
         node = node.parent
     return node
+
+
+def has_sibling_with_type(node: LN, type: int) -> bool:
+    # Check previous siblings
+    sibling = node.prev_sibling
+    while sibling is not None:
+        if sibling.type == type:
+            return True
+        sibling = sibling.prev_sibling
+
+    # Check next siblings
+    sibling = node.next_sibling
+    while sibling is not None:
+        if sibling.type == type:
+            return True
+        sibling = sibling.next_sibling
+
+    return False

src/black/output.py

@@ -6,7 +6,7 @@
 import json
 import re
 import tempfile
-from typing import Any, List, Optional
+from typing import Any, Optional
 
 from click import echo, style
 from mypy_extensions import mypyc_attr
@@ -59,7 +59,7 @@ def ipynb_diff(a: str, b: str, a_name: str, b_name: str) -> str:
 _line_pattern = re.compile(r"(.*?(?:\r\n|\n|\r|$))")
 
 
-def _splitlines_no_ff(source: str) -> List[str]:
+def _splitlines_no_ff(source: str) -> list[str]:
     """Split a string into lines ignoring form feed and other chars.
 
     This mimics how the Python parser splits source code.

src/black/parsing.py

@@ -4,7 +4,8 @@
 
 import ast
 import sys
-from typing import Iterable, Iterator, List, Set, Tuple
+import warnings
+from collections.abc import Collection, Iterator
 
 from black.mode import VERSION_TO_FEATURES, Feature, TargetVersion, supports_feature
 from black.nodes import syms
@@ -20,7 +21,7 @@ class InvalidInput(ValueError):
     """Raised when input source code fails all parse attempts."""
 
 
-def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
+def get_grammars(target_versions: set[TargetVersion]) -> list[Grammar]:
     if not target_versions:
         # No target_version specified, so try all grammars.
         return [
@@ -51,12 +52,20 @@ def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
     return grammars
 
 
-def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:
+def lib2to3_parse(
+    src_txt: str, target_versions: Collection[TargetVersion] = ()
+) -> Node:
     """Given a string with source, return the lib2to3 Node."""
     if not src_txt.endswith("\n"):
         src_txt += "\n"
 
     grammars = get_grammars(set(target_versions))
+    if target_versions:
+        max_tv = max(target_versions, key=lambda tv: tv.value)
+        tv_str = f" for target version {max_tv.pretty()}"
+    else:
+        tv_str = ""
+
     errors = {}
     for grammar in grammars:
         drv = driver.Driver(grammar)
@@ -72,14 +81,14 @@ def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -
             except IndexError:
                 faulty_line = "<line number missing in source>"
             errors[grammar.version] = InvalidInput(
-                f"Cannot parse: {lineno}:{column}: {faulty_line}"
+                f"Cannot parse{tv_str}: {lineno}:{column}: {faulty_line}"
             )
 
         except TokenError as te:
             # In edge cases these are raised; and typically don't have a "faulty_line".
             lineno, column = te.args[1]
             errors[grammar.version] = InvalidInput(
-                f"Cannot parse: {lineno}:{column}: {te.args[0]}"
+                f"Cannot parse{tv_str}: {lineno}:{column}: {te.args[0]}"
             )
 
     else:
@@ -109,13 +118,20 @@ def lib2to3_unparse(node: Node) -> str:
     return code
 
 
-def parse_single_version(
-    src: str, version: Tuple[int, int], *, type_comments: bool
+class ASTSafetyError(Exception):
+    """Raised when Black's generated code is not equivalent to the old AST."""
+
+
+def _parse_single_version(
+    src: str, version: tuple[int, int], *, type_comments: bool
 ) -> ast.AST:
     filename = "<unknown>"
-    return ast.parse(
-        src, filename, feature_version=version, type_comments=type_comments
-    )
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore", SyntaxWarning)
+        warnings.simplefilter("ignore", DeprecationWarning)
+        return ast.parse(
+            src, filename, feature_version=version, type_comments=type_comments
+        )
 
 
 def parse_ast(src: str) -> ast.AST:
@@ -125,7 +141,7 @@ def parse_ast(src: str) -> ast.AST:
     first_error = ""
     for version in sorted(versions, reverse=True):
         try:
-            return parse_single_version(src, version, type_comments=True)
+            return _parse_single_version(src, version, type_comments=True)
         except SyntaxError as e:
             if not first_error:
                 first_error = str(e)
@@ -133,7 +149,7 @@ def parse_ast(src: str) -> ast.AST:
     # Try to parse without type comments
     for version in sorted(versions, reverse=True):
         try:
-            return parse_single_version(src, version, type_comments=False)
+            return _parse_single_version(src, version, type_comments=False)
         except SyntaxError:
             pass
 
@@ -143,16 +159,27 @@ def parse_ast(src: str) -> ast.AST:
 def _normalize(lineend: str, value: str) -> str:
     # To normalize, we strip any leading and trailing space from
     # each line...
-    stripped: List[str] = [i.strip() for i in value.splitlines()]
+    stripped: list[str] = [i.strip() for i in value.splitlines()]
     normalized = lineend.join(stripped)
     # ...and remove any blank lines at the beginning and end of
     # the whole string
     return normalized.strip()
 
 
-def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
+def stringify_ast(node: ast.AST) -> Iterator[str]:
     """Simple visitor generating strings to compare ASTs by content."""
+    return _stringify_ast(node, [])
 
+
+def _stringify_ast_with_new_parent(
+    node: ast.AST, parent_stack: list[ast.AST], new_parent: ast.AST
+) -> Iterator[str]:
+    parent_stack.append(new_parent)
+    yield from _stringify_ast(node, parent_stack)
+    parent_stack.pop()
+
+
+def _stringify_ast(node: ast.AST, parent_stack: list[ast.AST]) -> Iterator[str]:
     if (
         isinstance(node, ast.Constant)
         and isinstance(node.value, str)
@@ -163,7 +190,7 @@ def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
         # over the kind
         node.kind = None
 
-    yield f"{'  ' * depth}{node.__class__.__name__}("
+    yield f"{'    ' * len(parent_stack)}{node.__class__.__name__}("
 
     for field in sorted(node._fields):  # noqa: F402
         # TypeIgnore has only one field 'lineno' which breaks this comparison
@@ -175,7 +202,7 @@ def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
         except AttributeError:
             continue
 
-        yield f"{'  ' * (depth + 1)}{field}="
+        yield f"{'    ' * (len(parent_stack) + 1)}{field}="
 
         if isinstance(value, list):
             for item in value:
@@ -186,14 +213,16 @@ def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
                     and isinstance(node, ast.Delete)
                     and isinstance(item, ast.Tuple)
                 ):
-                    for elt in item.elts:
-                        yield from stringify_ast(elt, depth + 2)
+                    for elt in _unwrap_tuples(item):
+                        yield from _stringify_ast_with_new_parent(
+                            elt, parent_stack, node
+                        )
 
                 elif isinstance(item, ast.AST):
-                    yield from stringify_ast(item, depth + 2)
+                    yield from _stringify_ast_with_new_parent(item, parent_stack, node)
 
         elif isinstance(value, ast.AST):
-            yield from stringify_ast(value, depth + 2)
+            yield from _stringify_ast_with_new_parent(value, parent_stack, node)
 
         else:
             normalized: object
@@ -201,6 +230,10 @@ def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
                 isinstance(node, ast.Constant)
                 and field == "value"
                 and isinstance(value, str)
+                and len(parent_stack) >= 2
+                # Any standalone string, ideally this would
+                # exactly match black.nodes.is_docstring
+                and isinstance(parent_stack[-1], ast.Expr)
             ):
                 # Constant strings may be indented across newlines, if they are
                 # docstrings; fold spaces after newlines when comparing. Similarly,
@@ -211,6 +244,17 @@ def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
                 normalized = value.rstrip()
             else:
                 normalized = value
-            yield f"{'  ' * (depth + 2)}{normalized!r},  # {value.__class__.__name__}"
+            yield (
+                f"{'    ' * (len(parent_stack) + 1)}{normalized!r},  #"
+                f" {value.__class__.__name__}"
+            )
 
-    yield f"{'  ' * depth})  # /{node.__class__.__name__}"
+    yield f"{'    ' * len(parent_stack)})  # /{node.__class__.__name__}"
+
+
+def _unwrap_tuples(node: ast.Tuple) -> Iterator[ast.AST]:
+    for elt in node.elts:
+        if isinstance(elt, ast.Tuple):
+            yield from _unwrap_tuples(elt)
+        else:
+            yield elt

src/black/ranges.py

@@ -1,8 +1,9 @@
 """Functions related to Black's formatting by line ranges feature."""
 
 import difflib
+from collections.abc import Collection, Iterator, Sequence
 from dataclasses import dataclass
-from typing import Collection, Iterator, List, Sequence, Set, Tuple, Union
+from typing import Union
 
 from black.nodes import (
     LN,
@@ -18,8 +19,8 @@
 from blib2to3.pgen2.token import ASYNC, NEWLINE
 
 
-def parse_line_ranges(line_ranges: Sequence[str]) -> List[Tuple[int, int]]:
-    lines: List[Tuple[int, int]] = []
+def parse_line_ranges(line_ranges: Sequence[str]) -> list[tuple[int, int]]:
+    lines: list[tuple[int, int]] = []
     for lines_str in line_ranges:
         parts = lines_str.split("-")
         if len(parts) != 2:
@@ -40,16 +41,44 @@ def parse_line_ranges(line_ranges: Sequence[str]) -> List[Tuple[int, int]]:
     return lines
 
 
-def is_valid_line_range(lines: Tuple[int, int]) -> bool:
+def is_valid_line_range(lines: tuple[int, int]) -> bool:
     """Returns whether the line range is valid."""
     return not lines or lines[0] <= lines[1]
 
 
+def sanitized_lines(
+    lines: Collection[tuple[int, int]], src_contents: str
+) -> Collection[tuple[int, int]]:
+    """Returns the valid line ranges for the given source.
+
+    This removes ranges that are entirely outside the valid lines.
+
+    Other ranges are normalized so that the start values are at least 1 and the
+    end values are at most the (1-based) index of the last source line.
+    """
+    if not src_contents:
+        return []
+    good_lines = []
+    src_line_count = src_contents.count("\n")
+    if not src_contents.endswith("\n"):
+        src_line_count += 1
+    for start, end in lines:
+        if start > src_line_count:
+            continue
+        # line-ranges are 1-based
+        start = max(start, 1)
+        if end < start:
+            continue
+        end = min(end, src_line_count)
+        good_lines.append((start, end))
+    return good_lines
+
+
 def adjusted_lines(
-    lines: Collection[Tuple[int, int]],
+    lines: Collection[tuple[int, int]],
     original_source: str,
     modified_source: str,
-) -> List[Tuple[int, int]]:
+) -> list[tuple[int, int]]:
     """Returns the adjusted line ranges based on edits from the original code.
 
     This computes the new line ranges by diffing original_source and
@@ -125,7 +154,7 @@ def adjusted_lines(
     return new_lines
 
 
-def convert_unchanged_lines(src_node: Node, lines: Collection[Tuple[int, int]]) -> None:
+def convert_unchanged_lines(src_node: Node, lines: Collection[tuple[int, int]]) -> None:
     """Converts unchanged lines to STANDALONE_COMMENT.
 
     The idea is similar to how `# fmt: on/off` is implemented. It also converts the
@@ -149,7 +178,7 @@ def convert_unchanged_lines(src_node: Node, lines: Collection[Tuple[int, int]])
     more formatting to pass (1). However, it's hard to get it correct when
     incorrect indentations are used. So we defer this to future optimizations.
     """
-    lines_set: Set[int] = set()
+    lines_set: set[int] = set()
     for start, end in lines:
         lines_set.update(range(start, end + 1))
     visitor = _TopLevelStatementsVisitor(lines_set)
@@ -177,7 +206,7 @@ class _TopLevelStatementsVisitor(Visitor[None]):
     classes/functions/statements.
     """
 
-    def __init__(self, lines_set: Set[int]):
+    def __init__(self, lines_set: set[int]):
         self._lines_set = lines_set
 
     def visit_simple_stmt(self, node: Node) -> Iterator[None]:
@@ -221,7 +250,7 @@ def visit_suite(self, node: Node) -> Iterator[None]:
             _convert_node_to_standalone_comment(semantic_parent)
 
 
-def _convert_unchanged_line_by_line(node: Node, lines_set: Set[int]) -> None:
+def _convert_unchanged_line_by_line(node: Node, lines_set: set[int]) -> None:
     """Converts unchanged to STANDALONE_COMMENT line by line."""
     for leaf in node.leaves():
         if leaf.type != NEWLINE:
@@ -233,7 +262,7 @@ def _convert_unchanged_line_by_line(node: Node, lines_set: Set[int]) -> None:
             #   match_stmt: "match" subject_expr ':' NEWLINE INDENT case_block+ DEDENT
             # Here we need to check `subject_expr`. The `case_block+` will be
             # checked by their own NEWLINEs.
-            nodes_to_ignore: List[LN] = []
+            nodes_to_ignore: list[LN] = []
             prev_sibling = leaf.prev_sibling
             while prev_sibling:
                 nodes_to_ignore.insert(0, prev_sibling)
@@ -354,7 +383,7 @@ def _leaf_line_end(leaf: Leaf) -> int:
         return leaf.lineno + str(leaf).count("\n")
 
 
-def _get_line_range(node_or_nodes: Union[LN, List[LN]]) -> Set[int]:
+def _get_line_range(node_or_nodes: Union[LN, list[LN]]) -> set[int]:
     """Returns the line range of this node or list of nodes."""
     if isinstance(node_or_nodes, list):
         nodes = node_or_nodes
@@ -435,7 +464,7 @@ def _calculate_lines_mappings(
         modified_source.splitlines(keepends=True),
     )
     matching_blocks = matcher.get_matching_blocks()
-    lines_mappings: List[_LinesMapping] = []
+    lines_mappings: list[_LinesMapping] = []
     # matching_blocks is a sequence of "same block of code ranges", see
     # https://docs.python.org/3/library/difflib.html#difflib.SequenceMatcher.get_matching_blocks
     # Each block corresponds to a _LinesMapping with is_changed_block=False,
@@ -487,10 +516,7 @@ def _find_lines_mapping_index(
     index = start_index
     while index < len(lines_mappings):
         mapping = lines_mappings[index]
-        if (
-            mapping.original_start <= original_line
-            and original_line <= mapping.original_end
-        ):
+        if mapping.original_start <= original_line <= mapping.original_end:
             return index
         index += 1
     return index

src/black/resources/black.schema.json

@@ -0,0 +1,148 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "$id": "https://github.com/psf/black/blob/main/src/black/resources/black.schema.json",
+  "$comment": "tool.black table in pyproject.toml",
+  "type": "object",
+  "additionalProperties": false,
+  "properties": {
+    "code": {
+      "type": "string",
+      "description": "Format the code passed in as a string."
+    },
+    "line-length": {
+      "type": "integer",
+      "description": "How many characters per line to allow.",
+      "default": 88
+    },
+    "target-version": {
+      "type": "array",
+      "items": {
+        "enum": [
+          "py33",
+          "py34",
+          "py35",
+          "py36",
+          "py37",
+          "py38",
+          "py39",
+          "py310",
+          "py311",
+          "py312",
+          "py313"
+        ]
+      },
+      "description": "Python versions that should be supported by Black's output. You should include all versions that your code supports. By default, Black will infer target versions from the project metadata in pyproject.toml. If this does not yield conclusive results, Black will use per-file auto-detection."
+    },
+    "pyi": {
+      "type": "boolean",
+      "description": "Format all input files like typing stubs regardless of file extension. This is useful when piping source on standard input.",
+      "default": false
+    },
+    "ipynb": {
+      "type": "boolean",
+      "description": "Format all input files like Jupyter Notebooks regardless of file extension. This is useful when piping source on standard input.",
+      "default": false
+    },
+    "python-cell-magics": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "When processing Jupyter Notebooks, add the given magic to the list of known python-magics (capture, prun, pypy, python, python3, time, timeit). Useful for formatting cells with custom python magics."
+    },
+    "skip-source-first-line": {
+      "type": "boolean",
+      "description": "Skip the first line of the source code.",
+      "default": false
+    },
+    "skip-string-normalization": {
+      "type": "boolean",
+      "description": "Don't normalize string quotes or prefixes.",
+      "default": false
+    },
+    "skip-magic-trailing-comma": {
+      "type": "boolean",
+      "description": "Don't use trailing commas as a reason to split lines.",
+      "default": false
+    },
+    "preview": {
+      "type": "boolean",
+      "description": "Enable potentially disruptive style changes that may be added to Black's main functionality in the next major release.",
+      "default": false
+    },
+    "unstable": {
+      "type": "boolean",
+      "description": "Enable potentially disruptive style changes that have known bugs or are not currently expected to make it into the stable style Black's next major release. Implies --preview.",
+      "default": false
+    },
+    "enable-unstable-feature": {
+      "type": "array",
+      "items": {
+        "enum": [
+          "string_processing",
+          "hug_parens_with_braces_and_square_brackets",
+          "wrap_long_dict_values_in_parens",
+          "multiline_string_handling",
+          "always_one_newline_after_import",
+          "fix_fmt_skip_in_one_liners"
+        ]
+      },
+      "description": "Enable specific features included in the `--unstable` style. Requires `--preview`. No compatibility guarantees are provided on the behavior or existence of any unstable features."
+    },
+    "check": {
+      "type": "boolean",
+      "description": "Don't write the files back, just return the status. Return code 0 means nothing would change. Return code 1 means some files would be reformatted. Return code 123 means there was an internal error.",
+      "default": false
+    },
+    "diff": {
+      "type": "boolean",
+      "description": "Don't write the files back, just output a diff to indicate what changes Black would've made. They are printed to stdout so capturing them is simple.",
+      "default": false
+    },
+    "color": {
+      "type": "boolean",
+      "description": "Show (or do not show) colored diff. Only applies when --diff is given.",
+      "default": false
+    },
+    "fast": {
+      "type": "boolean",
+      "description": "By default, Black performs an AST safety check after formatting your code. The --fast flag turns off this check and the --safe flag explicitly enables it. [default: --safe]",
+      "default": false
+    },
+    "required-version": {
+      "type": "string",
+      "description": "Require a specific version of Black to be running. This is useful for ensuring that all contributors to your project are using the same version, because different versions of Black may format code a little differently. This option can be set in a configuration file for consistent results across environments."
+    },
+    "exclude": {
+      "type": "string",
+      "description": "A regular expression that matches files and directories that should be excluded on recursive searches. An empty value means no paths are excluded. Use forward slashes for directories on all platforms (Windows, too). By default, Black also ignores all paths listed in .gitignore. Changing this value will override all default exclusions. [default: /(\\.direnv|\\.eggs|\\.git|\\.hg|\\.ipynb_checkpoints|\\.mypy_cache|\\.nox|\\.pytest_cache|\\.ruff_cache|\\.tox|\\.svn|\\.venv|\\.vscode|__pypackages__|_build|buck-out|build|dist|venv)/]"
+    },
+    "extend-exclude": {
+      "type": "string",
+      "description": "Like --exclude, but adds additional files and directories on top of the default values instead of overriding them."
+    },
+    "force-exclude": {
+      "type": "string",
+      "description": "Like --exclude, but files and directories matching this regex will be excluded even when they are passed explicitly as arguments. This is useful when invoking Black programmatically on changed files, such as in a pre-commit hook or editor plugin."
+    },
+    "include": {
+      "type": "string",
+      "description": "A regular expression that matches files and directories that should be included on recursive searches. An empty value means all files are included regardless of the name. Use forward slashes for directories on all platforms (Windows, too). Overrides all exclusions, including from .gitignore and command line options.",
+      "default": "(\\.pyi?|\\.ipynb)$"
+    },
+    "workers": {
+      "type": "integer",
+      "description": "When Black formats multiple files, it may use a process pool to speed up formatting. This option controls the number of parallel workers. This can also be specified via the BLACK_NUM_WORKERS environment variable. Defaults to the number of CPUs in the system."
+    },
+    "quiet": {
+      "type": "boolean",
+      "description": "Stop emitting all non-critical output. Error messages will still be emitted (which can silenced by 2>/dev/null).",
+      "default": false
+    },
+    "verbose": {
+      "type": "boolean",
+      "description": "Emit messages about files that were not changed or were ignored due to exclusion patterns. If Black is using a configuration file, a message detailing which one it is using will be emitted.",
+      "default": false
+    }
+  }
+}

src/black/schema.py

@@ -0,0 +1,15 @@
+import importlib.resources
+import json
+from typing import Any
+
+
+def get_schema(tool_name: str = "black") -> Any:
+    """Get the stored complete schema for black's settings."""
+    assert tool_name == "black", "Only black is supported."
+
+    pkg = "black.resources"
+    fname = "black.schema.json"
+
+    schema = importlib.resources.files(pkg).joinpath(fname)
+    with schema.open(encoding="utf-8") as f:
+        return json.load(f)

src/black/strings.py

@@ -5,7 +5,8 @@
 import re
 import sys
 from functools import lru_cache
-from typing import Final, List, Match, Pattern
+from re import Match, Pattern
+from typing import Final
 
 from black._width_table import WIDTH_TABLE
 from blib2to3.pytree import Leaf
@@ -14,7 +15,6 @@
 STRING_PREFIX_RE: Final = re.compile(
     r"^([" + STRING_PREFIX_CHARS + r"]*)(.*)$", re.DOTALL
 )
-FIRST_NON_WHITESPACE_RE: Final = re.compile(r"\s*\t+\s*(\S)")
 UNICODE_ESCAPE_RE: Final = re.compile(
     r"(?P<backslashes>\\+)(?P<body>"
     r"(u(?P<u>[a-fA-F0-9]{4}))"  # Character with 16-bit hex value xxxx
@@ -44,32 +44,28 @@ def has_triple_quotes(string: str) -> bool:
     return raw_string[:3] in {'"""', "'''"}
 
 
-def lines_with_leading_tabs_expanded(s: str) -> List[str]:
+def lines_with_leading_tabs_expanded(s: str) -> list[str]:
     """
     Splits string into lines and expands only leading tabs (following the normal
     Python rules)
     """
     lines = []
     for line in s.splitlines():
-        # Find the index of the first non-whitespace character after a string of
-        # whitespace that includes at least one tab
-        match = FIRST_NON_WHITESPACE_RE.match(line)
-        if match:
-            first_non_whitespace_idx = match.start(1)
-
-            lines.append(
-                line[:first_non_whitespace_idx].expandtabs()
-                + line[first_non_whitespace_idx:]
-            )
-        else:
+        stripped_line = line.lstrip()
+        if not stripped_line or stripped_line == line:
             lines.append(line)
+        else:
+            prefix_length = len(line) - len(stripped_line)
+            prefix = line[:prefix_length].expandtabs()
+            lines.append(prefix + stripped_line)
+    if s.endswith("\n"):
+        lines.append("")
     return lines
 
 
-def fix_docstring(docstring: str, prefix: str) -> str:
+def fix_multiline_docstring(docstring: str, prefix: str) -> str:
     # https://www.python.org/dev/peps/pep-0257/#handling-docstring-indentation
-    if not docstring:
-        return ""
+    assert docstring, "INTERNAL ERROR: Multiline docstrings cannot be empty"
     lines = lines_with_leading_tabs_expanded(docstring)
     # Determine minimum indentation (first line doesn't count):
     indent = sys.maxsize
@@ -173,8 +169,7 @@ def _cached_compile(pattern: str) -> Pattern[str]:
 def normalize_string_quotes(s: str) -> str:
     """Prefer double quotes but only if it doesn't cause more escaping.
 
-    Adds or removes backslashes as appropriate. Doesn't parse and fix
-    strings nested in f-strings.
+    Adds or removes backslashes as appropriate.
     """
     value = s.lstrip(STRING_PREFIX_CHARS)
     if value[:3] == '"""':
@@ -190,8 +185,7 @@ def normalize_string_quotes(s: str) -> str:
         orig_quote = "'"
         new_quote = '"'
     first_quote_pos = s.find(orig_quote)
-    if first_quote_pos == -1:
-        return s  # There's an internal error
+    assert first_quote_pos != -1, f"INTERNAL ERROR: Malformed string {s!r}"
 
     prefix = s[:first_quote_pos]
     unescaped_new_quote = _cached_compile(rf"(([^\\]|^)(\\\\)*){new_quote}")
@@ -215,6 +209,7 @@ def normalize_string_quotes(s: str) -> str:
             s = f"{prefix}{orig_quote}{body}{orig_quote}"
         new_body = sub_twice(escaped_orig_quote, rf"\1\2{orig_quote}", new_body)
         new_body = sub_twice(unescaped_new_quote, rf"\1\\{new_quote}", new_body)
+
     if "f" in prefix.casefold():
         matches = re.findall(
             r"""
@@ -244,6 +239,71 @@ def normalize_string_quotes(s: str) -> str:
     return f"{prefix}{new_quote}{new_body}{new_quote}"
 
 
+def normalize_fstring_quotes(
+    quote: str,
+    middles: list[Leaf],
+    is_raw_fstring: bool,
+) -> tuple[list[Leaf], str]:
+    """Prefer double quotes but only if it doesn't cause more escaping.
+
+    Adds or removes backslashes as appropriate.
+    """
+    if quote == '"""':
+        return middles, quote
+
+    elif quote == "'''":
+        new_quote = '"""'
+    elif quote == '"':
+        new_quote = "'"
+    else:
+        new_quote = '"'
+
+    unescaped_new_quote = _cached_compile(rf"(([^\\]|^)(\\\\)*){new_quote}")
+    escaped_new_quote = _cached_compile(rf"([^\\]|^)\\((?:\\\\)*){new_quote}")
+    escaped_orig_quote = _cached_compile(rf"([^\\]|^)\\((?:\\\\)*){quote}")
+    if is_raw_fstring:
+        for middle in middles:
+            if unescaped_new_quote.search(middle.value):
+                # There's at least one unescaped new_quote in this raw string
+                # so converting is impossible
+                return middles, quote
+
+        # Do not introduce or remove backslashes in raw strings, just use double quote
+        return middles, '"'
+
+    new_segments = []
+    for middle in middles:
+        segment = middle.value
+        # remove unnecessary escapes
+        new_segment = sub_twice(escaped_new_quote, rf"\1\2{new_quote}", segment)
+        if segment != new_segment:
+            # Consider the string without unnecessary escapes as the original
+            middle.value = new_segment
+
+        new_segment = sub_twice(escaped_orig_quote, rf"\1\2{quote}", new_segment)
+        new_segment = sub_twice(unescaped_new_quote, rf"\1\\{new_quote}", new_segment)
+        new_segments.append(new_segment)
+
+    if new_quote == '"""' and new_segments[-1].endswith('"'):
+        # edge case:
+        new_segments[-1] = new_segments[-1][:-1] + '\\"'
+
+    for middle, new_segment in zip(middles, new_segments):
+        orig_escape_count = middle.value.count("\\")
+        new_escape_count = new_segment.count("\\")
+
+    if new_escape_count > orig_escape_count:
+        return middles, quote  # Do not introduce more escaping
+
+    if new_escape_count == orig_escape_count and quote == '"':
+        return middles, quote  # Prefer double quotes
+
+    for middle, new_segment in zip(middles, new_segments):
+        middle.value = new_segment
+
+    return middles, new_quote
+
+
 def normalize_unicode_escape_sequences(leaf: Leaf) -> None:
     """Replace hex codes in Unicode escape sequences with lowercase representation."""
     text = leaf.value

src/black/trans.py

@@ -5,25 +5,9 @@
 import re
 from abc import ABC, abstractmethod
 from collections import defaultdict
+from collections.abc import Callable, Collection, Iterable, Iterator, Sequence
 from dataclasses import dataclass
-from typing import (
-    Any,
-    Callable,
-    ClassVar,
-    Collection,
-    Dict,
-    Final,
-    Iterable,
-    Iterator,
-    List,
-    Literal,
-    Optional,
-    Sequence,
-    Set,
-    Tuple,
-    TypeVar,
-    Union,
-)
+from typing import Any, ClassVar, Final, Literal, Optional, TypeVar, Union
 
 from mypy_extensions import trait
 
@@ -68,7 +52,7 @@ class CannotTransform(Exception):
 ParserState = int
 StringID = int
 TResult = Result[T, CannotTransform]  # (T)ransform Result
-TMatchResult = TResult[List[Index]]
+TMatchResult = TResult[list[Index]]
 
 SPLIT_SAFE_CHARS = frozenset(["\u3001", "\u3002", "\uff0c"])  # East Asian stops
 
@@ -94,43 +78,30 @@ def hug_power_op(
     else:
         raise CannotTransform("No doublestar token was found in the line.")
 
-    def is_simple_lookup(index: int, step: Literal[1, -1]) -> bool:
+    def is_simple_lookup(index: int, kind: Literal[1, -1]) -> bool:
         # Brackets and parentheses indicate calls, subscripts, etc. ...
         # basically stuff that doesn't count as "simple". Only a NAME lookup
         # or dotted lookup (eg. NAME.NAME) is OK.
-        if step == -1:
-            disallowed = {token.RPAR, token.RSQB}
+        if kind == -1:
+            return handle_is_simple_look_up_prev(line, index, {token.RPAR, token.RSQB})
         else:
-            disallowed = {token.LPAR, token.LSQB}
+            return handle_is_simple_lookup_forward(
+                line, index, {token.LPAR, token.LSQB}
+            )
 
-        while 0 <= index < len(line.leaves):
-            current = line.leaves[index]
-            if current.type in disallowed:
-                return False
-            if current.type not in {token.NAME, token.DOT} or current.value == "for":
-                # If the current token isn't disallowed, we'll assume this is simple as
-                # only the disallowed tokens are semantically attached to this lookup
-                # expression we're checking. Also, stop early if we hit the 'for' bit
-                # of a comprehension.
-                return True
-
-            index += step
-
-        return True
-
-    def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
+    def is_simple_operand(index: int, kind: Literal[1, -1]) -> bool:
         # An operand is considered "simple" if's a NAME, a numeric CONSTANT, a simple
         # lookup (see above), with or without a preceding unary operator.
         start = line.leaves[index]
         if start.type in {token.NAME, token.NUMBER}:
-            return is_simple_lookup(index, step=(1 if kind == "exponent" else -1))
+            return is_simple_lookup(index, kind)
 
         if start.type in {token.PLUS, token.MINUS, token.TILDE}:
             if line.leaves[index + 1].type in {token.NAME, token.NUMBER}:
-                # step is always one as bases with a preceding unary op will be checked
+                # kind is always one as bases with a preceding unary op will be checked
                 # for simplicity starting from the next token (so it'll hit the check
                 # above).
-                return is_simple_lookup(index + 1, step=1)
+                return is_simple_lookup(index + 1, kind=1)
 
         return False
 
@@ -145,9 +116,9 @@ def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
         should_hug = (
             (0 < idx < len(line.leaves) - 1)
             and leaf.type == token.DOUBLESTAR
-            and is_simple_operand(idx - 1, kind="base")
+            and is_simple_operand(idx - 1, kind=-1)
             and line.leaves[idx - 1].value != "lambda"
-            and is_simple_operand(idx + 1, kind="exponent")
+            and is_simple_operand(idx + 1, kind=1)
         )
         if should_hug:
             new_leaf.prefix = ""
@@ -162,6 +133,75 @@ def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
     yield new_line
 
 
+def handle_is_simple_look_up_prev(line: Line, index: int, disallowed: set[int]) -> bool:
+    """
+    Handling the determination of is_simple_lookup for the lines prior to the doublestar
+    token. This is required because of the need to isolate the chained expression
+    to determine the bracket or parenthesis belong to the single expression.
+    """
+    contains_disallowed = False
+    chain = []
+
+    while 0 <= index < len(line.leaves):
+        current = line.leaves[index]
+        chain.append(current)
+        if not contains_disallowed and current.type in disallowed:
+            contains_disallowed = True
+        if not is_expression_chained(chain):
+            return not contains_disallowed
+
+        index -= 1
+
+    return True
+
+
+def handle_is_simple_lookup_forward(
+    line: Line, index: int, disallowed: set[int]
+) -> bool:
+    """
+    Handling decision is_simple_lookup for the lines behind the doublestar token.
+    This function is simplified to keep consistent with the prior logic and the forward
+    case are more straightforward and do not need to care about chained expressions.
+    """
+    while 0 <= index < len(line.leaves):
+        current = line.leaves[index]
+        if current.type in disallowed:
+            return False
+        if current.type not in {token.NAME, token.DOT} or (
+            current.type == token.NAME and current.value == "for"
+        ):
+            # If the current token isn't disallowed, we'll assume this is simple as
+            # only the disallowed tokens are semantically attached to this lookup
+            # expression we're checking. Also, stop early if we hit the 'for' bit
+            # of a comprehension.
+            return True
+
+        index += 1
+
+    return True
+
+
+def is_expression_chained(chained_leaves: list[Leaf]) -> bool:
+    """
+    Function to determine if the variable is a chained call.
+    (e.g., foo.lookup, foo().lookup, (foo.lookup())) will be recognized as chained call)
+    """
+    if len(chained_leaves) < 2:
+        return True
+
+    current_leaf = chained_leaves[-1]
+    past_leaf = chained_leaves[-2]
+
+    if past_leaf.type == token.NAME:
+        return current_leaf.type in {token.DOT}
+    elif past_leaf.type in {token.RPAR, token.RSQB}:
+        return current_leaf.type in {token.RSQB, token.RPAR}
+    elif past_leaf.type in {token.LPAR, token.LSQB}:
+        return current_leaf.type in {token.NAME, token.LPAR, token.LSQB}
+    else:
+        return False
+
+
 class StringTransformer(ABC):
     """
     An implementation of the Transformer protocol that relies on its
@@ -212,7 +252,7 @@ def do_match(self, line: Line) -> TMatchResult:
 
     @abstractmethod
     def do_transform(
-        self, line: Line, string_indices: List[int]
+        self, line: Line, string_indices: list[int]
     ) -> Iterator[TResult[Line]]:
         """
         Yields:
@@ -302,8 +342,8 @@ class CustomSplitMapMixin:
     the resultant substrings go over the configured max line length.
     """
 
-    _Key: ClassVar = Tuple[StringID, str]
-    _CUSTOM_SPLIT_MAP: ClassVar[Dict[_Key, Tuple[CustomSplit, ...]]] = defaultdict(
+    _Key: ClassVar = tuple[StringID, str]
+    _CUSTOM_SPLIT_MAP: ClassVar[dict[_Key, tuple[CustomSplit, ...]]] = defaultdict(
         tuple
     )
 
@@ -327,7 +367,7 @@ def add_custom_splits(
         key = self._get_key(string)
         self._CUSTOM_SPLIT_MAP[key] = tuple(custom_splits)
 
-    def pop_custom_splits(self, string: str) -> List[CustomSplit]:
+    def pop_custom_splits(self, string: str) -> list[CustomSplit]:
         """Custom Split Map Getter Method
 
         Returns:
@@ -402,7 +442,7 @@ def do_match(self, line: Line) -> TMatchResult:
                         break
                     i += 1
 
-                if not is_part_of_annotation(leaf) and not contains_comment:
+                if not contains_comment and not is_part_of_annotation(leaf):
                     string_indices.append(idx)
 
                 # Advance to the next non-STRING leaf.
@@ -426,7 +466,7 @@ def do_match(self, line: Line) -> TMatchResult:
             return TErr("This line has no strings that need merging.")
 
     def do_transform(
-        self, line: Line, string_indices: List[int]
+        self, line: Line, string_indices: list[int]
     ) -> Iterator[TResult[Line]]:
         new_line = line
 
@@ -457,7 +497,7 @@ def do_transform(
 
     @staticmethod
     def _remove_backslash_line_continuation_chars(
-        line: Line, string_indices: List[int]
+        line: Line, string_indices: list[int]
     ) -> TResult[Line]:
         """
         Merge strings that were split across multiple lines using
@@ -498,7 +538,7 @@ def _remove_backslash_line_continuation_chars(
         return Ok(new_line)
 
     def _merge_string_group(
-        self, line: Line, string_indices: List[int]
+        self, line: Line, string_indices: list[int]
     ) -> TResult[Line]:
         """
         Merges string groups (i.e. set of adjacent strings).
@@ -517,7 +557,7 @@ def _merge_string_group(
         is_valid_index = is_valid_index_factory(LL)
 
         # A dict of {string_idx: tuple[num_of_strings, string_leaf]}.
-        merged_string_idx_dict: Dict[int, Tuple[int, Leaf]] = {}
+        merged_string_idx_dict: dict[int, tuple[int, Leaf]] = {}
         for string_idx in string_indices:
             vresult = self._validate_msg(line, string_idx)
             if isinstance(vresult, Err):
@@ -553,8 +593,8 @@ def _merge_string_group(
         return Ok(new_line)
 
     def _merge_one_string_group(
-        self, LL: List[Leaf], string_idx: int, is_valid_index: Callable[[int], bool]
-    ) -> Tuple[int, Leaf]:
+        self, LL: list[Leaf], string_idx: int, is_valid_index: Callable[[int], bool]
+    ) -> tuple[int, Leaf]:
         """
         Merges one string group where the first string in the group is
         `LL[string_idx]`.
@@ -590,10 +630,10 @@ def make_naked(string: str, string_prefix: str) -> str:
             """
             assert_is_leaf_string(string)
             if "f" in string_prefix:
-                f_expressions = (
+                f_expressions = [
                     string[span[0] + 1 : span[1] - 1]  # +-1 to get rid of curly braces
                     for span in iter_fexpr_spans(string)
-                )
+                ]
                 debug_expressions_contain_visible_quotes = any(
                     re.search(r".*[\'\"].*(?<![!:=])={1}(?!=)(?![^\s:])", expression)
                     for expression in f_expressions
@@ -724,6 +764,8 @@ def _validate_msg(line: Line, string_idx: int) -> TResult[None]:
                 - The set of all string prefixes in the string group is of
                   length greater than one and is not equal to {"", "f"}.
                 - The string group consists of raw strings.
+                - The string group would merge f-strings with different quote types
+                  and internal quotes.
                 - The string group is stringified type annotations. We don't want to
                   process stringified type annotations since pyright doesn't support
                   them spanning multiple string values. (NOTE: mypy, pytype, pyre do
@@ -750,6 +792,8 @@ def _validate_msg(line: Line, string_idx: int) -> TResult[None]:
 
                 i += inc
 
+        QUOTE = line.leaves[string_idx].value[-1]
+
         num_of_inline_string_comments = 0
         set_of_prefixes = set()
         num_of_strings = 0
@@ -772,6 +816,19 @@ def _validate_msg(line: Line, string_idx: int) -> TResult[None]:
 
             set_of_prefixes.add(prefix)
 
+            if (
+                "f" in prefix
+                and leaf.value[-1] != QUOTE
+                and (
+                    "'" in leaf.value[len(prefix) + 1 : -1]
+                    or '"' in leaf.value[len(prefix) + 1 : -1]
+                )
+            ):
+                return TErr(
+                    "StringMerger does NOT merge f-strings with different quote types"
+                    " and internal quotes."
+                )
+
             if id(leaf) in line.comments:
                 num_of_inline_string_comments += 1
                 if contains_pragma_comment(line.comments[id(leaf)]):
@@ -800,6 +857,7 @@ class StringParenStripper(StringTransformer):
         The line contains a string which is surrounded by parentheses and:
             - The target string is NOT the only argument to a function call.
             - The target string is NOT a "pointless" string.
+            - The target string is NOT a dictionary value.
             - If the target string contains a PERCENT, the brackets are not
               preceded or followed by an operator with higher precedence than
               PERCENT.
@@ -847,11 +905,14 @@ def do_match(self, line: Line) -> TMatchResult:
             ):
                 continue
 
-            # That LPAR should NOT be preceded by a function name or a closing
-            # bracket (which could be a function which returns a function or a
-            # list/dictionary that contains a function)...
+            # That LPAR should NOT be preceded by a colon (which could be a
+            # dictionary value), function name, or a closing bracket (which
+            # could be a function returning a function or a list/dictionary
+            # containing a function)...
             if is_valid_index(idx - 2) and (
-                LL[idx - 2].type == token.NAME or LL[idx - 2].type in CLOSING_BRACKETS
+                LL[idx - 2].type == token.COLON
+                or LL[idx - 2].type == token.NAME
+                or LL[idx - 2].type in CLOSING_BRACKETS
             ):
                 continue
 
@@ -918,11 +979,11 @@ def do_match(self, line: Line) -> TMatchResult:
         return TErr("This line has no strings wrapped in parens.")
 
     def do_transform(
-        self, line: Line, string_indices: List[int]
+        self, line: Line, string_indices: list[int]
     ) -> Iterator[TResult[Line]]:
         LL = line.leaves
 
-        string_and_rpar_indices: List[int] = []
+        string_and_rpar_indices: list[int] = []
         for string_idx in string_indices:
             string_parser = StringParser()
             rpar_idx = string_parser.parse(LL, string_idx)
@@ -945,7 +1006,7 @@ def do_transform(
             )
 
     def _transform_to_new_line(
-        self, line: Line, string_and_rpar_indices: List[int]
+        self, line: Line, string_and_rpar_indices: list[int]
     ) -> Line:
         LL = line.leaves
 
@@ -1198,7 +1259,7 @@ def _get_max_string_length(self, line: Line, string_idx: int) -> int:
         return max_string_length
 
     @staticmethod
-    def _prefer_paren_wrap_match(LL: List[Leaf]) -> Optional[int]:
+    def _prefer_paren_wrap_match(LL: list[Leaf]) -> Optional[int]:
         """
         Returns:
             string_idx such that @LL[string_idx] is equal to our target (i.e.
@@ -1243,14 +1304,14 @@ def _prefer_paren_wrap_match(LL: List[Leaf]) -> Optional[int]:
         return None
 
 
-def iter_fexpr_spans(s: str) -> Iterator[Tuple[int, int]]:
+def iter_fexpr_spans(s: str) -> Iterator[tuple[int, int]]:
     """
     Yields spans corresponding to expressions in a given f-string.
     Spans are half-open ranges (left inclusive, right exclusive).
     Assumes the input string is a valid f-string, but will not crash if the input
     string is invalid.
     """
-    stack: List[int] = []  # our curly paren stack
+    stack: list[int] = []  # our curly paren stack
     i = 0
     while i < len(s):
         if s[i] == "{":
@@ -1273,7 +1334,7 @@ def iter_fexpr_spans(s: str) -> Iterator[Tuple[int, int]]:
             i += 1
             continue
 
-        # if we're in an expression part of the f-string, fast forward through strings
+        # if we're in an expression part of the f-string, fast-forward through strings
         # note that backslashes are not legal in the expression portion of f-strings
         if stack:
             delim = None
@@ -1413,7 +1474,7 @@ def do_splitter_match(self, line: Line) -> TMatchResult:
         return Ok([string_idx])
 
     def do_transform(
-        self, line: Line, string_indices: List[int]
+        self, line: Line, string_indices: list[int]
     ) -> Iterator[TResult[Line]]:
         LL = line.leaves
         assert len(string_indices) == 1, (
@@ -1515,7 +1576,7 @@ def more_splits_should_be_made() -> bool:
             else:
                 return str_width(rest_value) > max_last_string_column()
 
-        string_line_results: List[Ok[Line]] = []
+        string_line_results: list[Ok[Line]] = []
         while more_splits_should_be_made():
             if use_custom_breakpoints:
                 # Custom User Split (manual)
@@ -1644,7 +1705,7 @@ def more_splits_should_be_made() -> bool:
             last_line.comments = line.comments.copy()
             yield Ok(last_line)
 
-    def _iter_nameescape_slices(self, string: str) -> Iterator[Tuple[Index, Index]]:
+    def _iter_nameescape_slices(self, string: str) -> Iterator[tuple[Index, Index]]:
         """
         Yields:
             All ranges of @string which, if @string were to be split there,
@@ -1675,7 +1736,7 @@ def _iter_nameescape_slices(self, string: str) -> Iterator[Tuple[Index, Index]]:
                 raise RuntimeError(f"{self.__class__.__name__} LOGIC ERROR!")
             yield begin, end
 
-    def _iter_fexpr_slices(self, string: str) -> Iterator[Tuple[Index, Index]]:
+    def _iter_fexpr_slices(self, string: str) -> Iterator[tuple[Index, Index]]:
         """
         Yields:
             All ranges of @string which, if @string were to be split there,
@@ -1686,8 +1747,8 @@ def _iter_fexpr_slices(self, string: str) -> Iterator[Tuple[Index, Index]]:
             return
         yield from iter_fexpr_spans(string)
 
-    def _get_illegal_split_indices(self, string: str) -> Set[Index]:
-        illegal_indices: Set[Index] = set()
+    def _get_illegal_split_indices(self, string: str) -> set[Index]:
+        illegal_indices: set[Index] = set()
         iterators = [
             self._iter_fexpr_slices(string),
             self._iter_nameescape_slices(string),
@@ -1740,7 +1801,7 @@ def passes_all_checks(i: Index) -> bool:
             """
             Returns:
                 True iff ALL of the conditions listed in the 'Transformations'
-                section of this classes' docstring would be be met by returning @i.
+                section of this classes' docstring would be met by returning @i.
             """
             is_space = string[i] == " "
             is_split_safe = is_valid_index(i - 1) and string[i - 1] in SPLIT_SAFE_CHARS
@@ -1813,7 +1874,7 @@ def _normalize_f_string(self, string: str, prefix: str) -> str:
         else:
             return string
 
-    def _get_string_operator_leaves(self, leaves: Iterable[Leaf]) -> List[Leaf]:
+    def _get_string_operator_leaves(self, leaves: Iterable[Leaf]) -> list[Leaf]:
         LL = list(leaves)
 
         string_op_leaves = []
@@ -1922,7 +1983,7 @@ def do_splitter_match(self, line: Line) -> TMatchResult:
         return TErr("This line does not contain any non-atomic strings.")
 
     @staticmethod
-    def _return_match(LL: List[Leaf]) -> Optional[int]:
+    def _return_match(LL: list[Leaf]) -> Optional[int]:
         """
         Returns:
             string_idx such that @LL[string_idx] is equal to our target (i.e.
@@ -1932,7 +1993,7 @@ def _return_match(LL: List[Leaf]) -> Optional[int]:
                 OR
             None, otherwise.
         """
-        # If this line is apart of a return/yield statement and the first leaf
+        # If this line is a part of a return/yield statement and the first leaf
         # contains either the "return" or "yield" keywords...
         if parent_type(LL[0]) in [syms.return_stmt, syms.yield_expr] and LL[
             0
@@ -1947,7 +2008,7 @@ def _return_match(LL: List[Leaf]) -> Optional[int]:
         return None
 
     @staticmethod
-    def _else_match(LL: List[Leaf]) -> Optional[int]:
+    def _else_match(LL: list[Leaf]) -> Optional[int]:
         """
         Returns:
             string_idx such that @LL[string_idx] is equal to our target (i.e.
@@ -1957,7 +2018,7 @@ def _else_match(LL: List[Leaf]) -> Optional[int]:
                 OR
             None, otherwise.
         """
-        # If this line is apart of a ternary expression and the first leaf
+        # If this line is a part of a ternary expression and the first leaf
         # contains the "else" keyword...
         if (
             parent_type(LL[0]) == syms.test
@@ -1974,7 +2035,7 @@ def _else_match(LL: List[Leaf]) -> Optional[int]:
         return None
 
     @staticmethod
-    def _assert_match(LL: List[Leaf]) -> Optional[int]:
+    def _assert_match(LL: list[Leaf]) -> Optional[int]:
         """
         Returns:
             string_idx such that @LL[string_idx] is equal to our target (i.e.
@@ -1984,7 +2045,7 @@ def _assert_match(LL: List[Leaf]) -> Optional[int]:
                 OR
             None, otherwise.
         """
-        # If this line is apart of an assert statement and the first leaf
+        # If this line is a part of an assert statement and the first leaf
         # contains the "assert" keyword...
         if parent_type(LL[0]) == syms.assert_stmt and LL[0].value == "assert":
             is_valid_index = is_valid_index_factory(LL)
@@ -2009,7 +2070,7 @@ def _assert_match(LL: List[Leaf]) -> Optional[int]:
         return None
 
     @staticmethod
-    def _assign_match(LL: List[Leaf]) -> Optional[int]:
+    def _assign_match(LL: list[Leaf]) -> Optional[int]:
         """
         Returns:
             string_idx such that @LL[string_idx] is equal to our target (i.e.
@@ -2019,7 +2080,7 @@ def _assign_match(LL: List[Leaf]) -> Optional[int]:
                 OR
             None, otherwise.
         """
-        # If this line is apart of an expression statement or is a function
+        # If this line is a part of an expression statement or is a function
         # argument AND the first leaf contains a variable name...
         if (
             parent_type(LL[0]) in [syms.expr_stmt, syms.argument, syms.power]
@@ -2040,7 +2101,7 @@ def _assign_match(LL: List[Leaf]) -> Optional[int]:
                         string_parser = StringParser()
                         idx = string_parser.parse(LL, string_idx)
 
-                        # The next leaf MAY be a comma iff this line is apart
+                        # The next leaf MAY be a comma iff this line is a part
                         # of a function argument...
                         if (
                             parent_type(LL[0]) == syms.argument
@@ -2056,7 +2117,7 @@ def _assign_match(LL: List[Leaf]) -> Optional[int]:
         return None
 
     @staticmethod
-    def _dict_or_lambda_match(LL: List[Leaf]) -> Optional[int]:
+    def _dict_or_lambda_match(LL: list[Leaf]) -> Optional[int]:
         """
         Returns:
             string_idx such that @LL[string_idx] is equal to our target (i.e.
@@ -2095,7 +2156,7 @@ def _dict_or_lambda_match(LL: List[Leaf]) -> Optional[int]:
         return None
 
     def do_transform(
-        self, line: Line, string_indices: List[int]
+        self, line: Line, string_indices: list[int]
     ) -> Iterator[TResult[Line]]:
         LL = line.leaves
         assert len(string_indices) == 1, (
@@ -2177,18 +2238,17 @@ def do_transform(
             elif right_leaves and right_leaves[-1].type == token.RPAR:
                 # Special case for lambda expressions as dict's value, e.g.:
                 #     my_dict = {
-                #        "key": lambda x: f"formatted: {x},
+                #        "key": lambda x: f"formatted: {x}",
                 #     }
                 # After wrapping the dict's value with parentheses, the string is
                 # followed by a RPAR but its opening bracket is lambda's, not
                 # the string's:
-                #        "key": (lambda x: f"formatted: {x}),
+                #        "key": (lambda x: f"formatted: {x}"),
                 opening_bracket = right_leaves[-1].opening_bracket
                 if opening_bracket is not None and opening_bracket in left_leaves:
                     index = left_leaves.index(opening_bracket)
                     if (
-                        index > 0
-                        and index < len(left_leaves) - 1
+                        0 < index < len(left_leaves) - 1
                         and left_leaves[index - 1].type == token.COLON
                         and left_leaves[index + 1].value == "lambda"
                     ):
@@ -2262,7 +2322,7 @@ class StringParser:
     DONE: Final = 8
 
     # Lookup Table for Next State
-    _goto: Final[Dict[Tuple[ParserState, NodeType], ParserState]] = {
+    _goto: Final[dict[tuple[ParserState, NodeType], ParserState]] = {
         # A string trailer may start with '.' OR '%'.
         (START, token.DOT): DOT,
         (START, token.PERCENT): PERCENT,
@@ -2291,13 +2351,13 @@ def __init__(self) -> None:
         self._state = self.START
         self._unmatched_lpars = 0
 
-    def parse(self, leaves: List[Leaf], string_idx: int) -> int:
+    def parse(self, leaves: list[Leaf], string_idx: int) -> int:
         """
         Pre-conditions:
             * @leaves[@string_idx].type == token.STRING
 
         Returns:
-            The index directly after the last leaf which is apart of the string
+            The index directly after the last leaf which is a part of the string
             trailer, if a "trailer" exists.
             OR
             @string_idx + 1, if no string "trailer" exists.
@@ -2320,7 +2380,7 @@ def _next_state(self, leaf: Leaf) -> bool:
               MUST be the leaf directly following @leaf.
 
         Returns:
-            True iff @leaf is apart of the string's trailer.
+            True iff @leaf is a part of the string's trailer.
         """
         # We ignore empty LPAR or RPAR leaves.
         if is_empty_par(leaf):

src/blackd/__init__.py

@@ -2,12 +2,12 @@
 import logging
 from concurrent.futures import Executor, ProcessPoolExecutor
 from datetime import datetime, timezone
-from functools import partial
+from functools import cache, partial
 from multiprocessing import freeze_support
-from typing import Set, Tuple
 
 try:
     from aiohttp import web
+    from multidict import MultiMapping
 
     from .middlewares import cors
 except ImportError as ie:
@@ -34,6 +34,8 @@
 SKIP_STRING_NORMALIZATION_HEADER = "X-Skip-String-Normalization"
 SKIP_MAGIC_TRAILING_COMMA = "X-Skip-Magic-Trailing-Comma"
 PREVIEW = "X-Preview"
+UNSTABLE = "X-Unstable"
+ENABLE_UNSTABLE_FEATURE = "X-Enable-Unstable-Feature"
 FAST_OR_SAFE_HEADER = "X-Fast-Or-Safe"
 DIFF_HEADER = "X-Diff"
 
@@ -45,6 +47,8 @@
     SKIP_STRING_NORMALIZATION_HEADER,
     SKIP_MAGIC_TRAILING_COMMA,
     PREVIEW,
+    UNSTABLE,
+    ENABLE_UNSTABLE_FEATURE,
     FAST_OR_SAFE_HEADER,
     DIFF_HEADER,
 ]
@@ -53,6 +57,10 @@
 BLACK_VERSION_HEADER = "X-Black-Version"
 
 
+class HeaderError(Exception):
+    pass
+
+
 class InvalidVariantHeader(Exception):
     pass
 
@@ -77,12 +85,16 @@ def main(bind_host: str, bind_port: int) -> None:
     web.run_app(app, host=bind_host, port=bind_port, handle_signals=True, print=None)
 
 
+@cache
+def executor() -> Executor:
+    return ProcessPoolExecutor()
+
+
 def make_app() -> web.Application:
     app = web.Application(
         middlewares=[cors(allow_headers=(*BLACK_HEADERS, "Content-Type"))]
     )
-    executor = ProcessPoolExecutor()
-    app.add_routes([web.post("/", partial(handle, executor=executor))])
+    app.add_routes([web.post("/", partial(handle, executor=executor()))])
     return app
 
 
@@ -93,55 +105,21 @@ async def handle(request: web.Request, executor: Executor) -> web.Response:
             return web.Response(
                 status=501, text="This server only supports protocol version 1"
             )
-        try:
-            line_length = int(
-                request.headers.get(LINE_LENGTH_HEADER, black.DEFAULT_LINE_LENGTH)
-            )
-        except ValueError:
-            return web.Response(status=400, text="Invalid line length header value")
 
-        if PYTHON_VARIANT_HEADER in request.headers:
-            value = request.headers[PYTHON_VARIANT_HEADER]
-            try:
-                pyi, versions = parse_python_variant_header(value)
-            except InvalidVariantHeader as e:
-                return web.Response(
-                    status=400,
-                    text=f"Invalid value for {PYTHON_VARIANT_HEADER}: {e.args[0]}",
-                )
-        else:
-            pyi = False
-            versions = set()
-
-        skip_string_normalization = bool(
-            request.headers.get(SKIP_STRING_NORMALIZATION_HEADER, False)
-        )
-        skip_magic_trailing_comma = bool(
-            request.headers.get(SKIP_MAGIC_TRAILING_COMMA, False)
-        )
-        skip_source_first_line = bool(
-            request.headers.get(SKIP_SOURCE_FIRST_LINE, False)
-        )
-        preview = bool(request.headers.get(PREVIEW, False))
         fast = False
         if request.headers.get(FAST_OR_SAFE_HEADER, "safe") == "fast":
             fast = True
-        mode = black.FileMode(
-            target_versions=versions,
-            is_pyi=pyi,
-            line_length=line_length,
-            skip_source_first_line=skip_source_first_line,
-            string_normalization=not skip_string_normalization,
-            magic_trailing_comma=not skip_magic_trailing_comma,
-            preview=preview,
-        )
+        try:
+            mode = parse_mode(request.headers)
+        except HeaderError as e:
+            return web.Response(status=400, text=e.args[0])
         req_bytes = await request.content.read()
         charset = request.charset if request.charset is not None else "utf8"
         req_str = req_bytes.decode(charset)
         then = datetime.now(timezone.utc)
 
         header = ""
-        if skip_source_first_line:
+        if mode.skip_source_first_line:
             first_newline_position: int = req_str.find("\n") + 1
             header = req_str[:first_newline_position]
             req_str = req_str[first_newline_position:]
@@ -190,7 +168,58 @@ async def handle(request: web.Request, executor: Executor) -> web.Response:
         return web.Response(status=500, headers=headers, text=str(e))
 
 
-def parse_python_variant_header(value: str) -> Tuple[bool, Set[black.TargetVersion]]:
+def parse_mode(headers: MultiMapping[str]) -> black.Mode:
+    try:
+        line_length = int(headers.get(LINE_LENGTH_HEADER, black.DEFAULT_LINE_LENGTH))
+    except ValueError:
+        raise HeaderError("Invalid line length header value") from None
+
+    if PYTHON_VARIANT_HEADER in headers:
+        value = headers[PYTHON_VARIANT_HEADER]
+        try:
+            pyi, versions = parse_python_variant_header(value)
+        except InvalidVariantHeader as e:
+            raise HeaderError(
+                f"Invalid value for {PYTHON_VARIANT_HEADER}: {e.args[0]}",
+            ) from None
+    else:
+        pyi = False
+        versions = set()
+
+    skip_string_normalization = bool(
+        headers.get(SKIP_STRING_NORMALIZATION_HEADER, False)
+    )
+    skip_magic_trailing_comma = bool(headers.get(SKIP_MAGIC_TRAILING_COMMA, False))
+    skip_source_first_line = bool(headers.get(SKIP_SOURCE_FIRST_LINE, False))
+
+    preview = bool(headers.get(PREVIEW, False))
+    unstable = bool(headers.get(UNSTABLE, False))
+    enable_features: set[black.Preview] = set()
+    enable_unstable_features = headers.get(ENABLE_UNSTABLE_FEATURE, "").split(",")
+    for piece in enable_unstable_features:
+        piece = piece.strip()
+        if piece:
+            try:
+                enable_features.add(black.Preview[piece])
+            except KeyError:
+                raise HeaderError(
+                    f"Invalid value for {ENABLE_UNSTABLE_FEATURE}: {piece}",
+                ) from None
+
+    return black.FileMode(
+        target_versions=versions,
+        is_pyi=pyi,
+        line_length=line_length,
+        skip_source_first_line=skip_source_first_line,
+        string_normalization=not skip_string_normalization,
+        magic_trailing_comma=not skip_magic_trailing_comma,
+        preview=preview,
+        unstable=unstable,
+        enabled_features=enable_features,
+    )
+
+
+def parse_python_variant_header(value: str) -> tuple[bool, set[black.TargetVersion]]:
     if value == "pyi":
         return True, set()
     else:

src/blackd/middlewares.py

@@ -1,21 +1,11 @@
-from typing import TYPE_CHECKING, Any, Awaitable, Callable, Iterable, TypeVar
+from collections.abc import Awaitable, Callable, Iterable
 
+from aiohttp.typedefs import Middleware
+from aiohttp.web_middlewares import middleware
 from aiohttp.web_request import Request
 from aiohttp.web_response import StreamResponse
 
-if TYPE_CHECKING:
-    F = TypeVar("F", bound=Callable[..., Any])
-    middleware: Callable[[F], F]
-else:
-    try:
-        from aiohttp.web_middlewares import middleware
-    except ImportError:
-        # @middleware is deprecated and its behaviour is the default since aiohttp 4.0
-        # so if it doesn't exist anymore, define a no-op for forward compatibility.
-        middleware = lambda x: x  # noqa: E731
-
 Handler = Callable[[Request], Awaitable[StreamResponse]]
-Middleware = Callable[[Request, Handler], Awaitable[StreamResponse]]
 
 
 def cors(allow_headers: Iterable[str]) -> Middleware:

src/blib2to3/Grammar.txt

@@ -12,9 +12,9 @@ file_input: (NEWLINE | stmt)* ENDMARKER
 single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
 eval_input: testlist NEWLINE* ENDMARKER
 
-typevar: NAME [':' expr]
-paramspec: '**' NAME
-typevartuple: '*' NAME
+typevar: NAME [':' test] ['=' test]
+paramspec: '**' NAME ['=' test]
+typevartuple: '*' NAME ['=' (test|star_expr)]
 typeparam: typevar | paramspec | typevartuple
 typeparams: '[' typeparam (',' typeparam)* [','] ']'
 
@@ -163,7 +163,7 @@ atom: ('(' [yield_expr|testlist_gexp] ')' |
        '[' [listmaker] ']' |
        '{' [dictsetmaker] '}' |
        '`' testlist1 '`' |
-       NAME | NUMBER | STRING+ | '.' '.' '.')
+       NAME | NUMBER | (STRING | fstring)+ | '.' '.' '.')
 listmaker: (namedexpr_test|star_expr) ( old_comp_for | (',' (namedexpr_test|star_expr))* [','] )
 testlist_gexp: (namedexpr_test|star_expr) ( old_comp_for | (',' (namedexpr_test|star_expr))* [','] )
 lambdef: 'lambda' [varargslist] ':' test
@@ -254,3 +254,8 @@ case_block: "case" patterns [guard] ':' suite
 guard: 'if' namedexpr_test
 patterns: pattern (',' pattern)* [',']
 pattern: (expr|star_expr) ['as' expr]
+
+fstring: FSTRING_START fstring_middle* FSTRING_END
+fstring_middle: fstring_replacement_field | FSTRING_MIDDLE
+fstring_replacement_field: '{' (yield_expr | testlist_star_expr) ['='] [ "!" NAME ] [ ':' fstring_format_spec* ] '}'
+fstring_format_spec: FSTRING_MIDDLE | fstring_replacement_field

src/blib2to3/pgen2/driver.py

@@ -21,13 +21,14 @@
 import os
 import pkgutil
 import sys
+from collections.abc import Iterable, Iterator
 from contextlib import contextmanager
 from dataclasses import dataclass, field
 from logging import Logger
-from typing import IO, Any, Iterable, Iterator, List, Optional, Tuple, Union, cast
+from typing import IO, Any, Optional, Union, cast
 
 from blib2to3.pgen2.grammar import Grammar
-from blib2to3.pgen2.tokenize import GoodTokenInfo
+from blib2to3.pgen2.tokenize import TokenInfo
 from blib2to3.pytree import NL
 
 # Pgen imports
@@ -40,7 +41,7 @@
 class ReleaseRange:
     start: int
     end: Optional[int] = None
-    tokens: List[Any] = field(default_factory=list)
+    tokens: list[Any] = field(default_factory=list)
 
     def lock(self) -> None:
         total_eaten = len(self.tokens)
@@ -51,7 +52,7 @@ class TokenProxy:
     def __init__(self, generator: Any) -> None:
         self._tokens = generator
         self._counter = 0
-        self._release_ranges: List[ReleaseRange] = []
+        self._release_ranges: list[ReleaseRange] = []
 
     @contextmanager
     def release(self) -> Iterator["TokenProxy"]:
@@ -111,7 +112,7 @@ def __init__(self, grammar: Grammar, logger: Optional[Logger] = None) -> None:
             logger = logging.getLogger(__name__)
         self.logger = logger
 
-    def parse_tokens(self, tokens: Iterable[GoodTokenInfo], debug: bool = False) -> NL:
+    def parse_tokens(self, tokens: Iterable[TokenInfo], debug: bool = False) -> NL:
         """Parse a series of tokens and return the syntax tree."""
         # XXX Move the prefix computation into a wrapper around tokenize.
         proxy = TokenProxy(tokens)
@@ -121,7 +122,7 @@ def parse_tokens(self, tokens: Iterable[GoodTokenInfo], debug: bool = False) ->
 
         lineno = 1
         column = 0
-        indent_columns: List[int] = []
+        indent_columns: list[int] = []
         type = value = start = end = line_text = None
         prefix = ""
 
@@ -167,7 +168,9 @@ def parse_tokens(self, tokens: Iterable[GoodTokenInfo], debug: bool = False) ->
             if type in {token.INDENT, token.DEDENT}:
                 prefix = _prefix
             lineno, column = end
-            if value.endswith("\n"):
+            # FSTRING_MIDDLE is the only token that can end with a newline, and
+            # `end` will point to the next line. For that case, don't increment lineno.
+            if value.endswith("\n") and type != token.FSTRING_MIDDLE:
                 lineno += 1
                 column = 0
         else:
@@ -177,31 +180,21 @@ def parse_tokens(self, tokens: Iterable[GoodTokenInfo], debug: bool = False) ->
         assert p.rootnode is not None
         return p.rootnode
 
-    def parse_stream_raw(self, stream: IO[str], debug: bool = False) -> NL:
-        """Parse a stream and return the syntax tree."""
-        tokens = tokenize.generate_tokens(stream.readline, grammar=self.grammar)
-        return self.parse_tokens(tokens, debug)
-
-    def parse_stream(self, stream: IO[str], debug: bool = False) -> NL:
-        """Parse a stream and return the syntax tree."""
-        return self.parse_stream_raw(stream, debug)
-
     def parse_file(
         self, filename: Path, encoding: Optional[str] = None, debug: bool = False
     ) -> NL:
         """Parse a file and return the syntax tree."""
         with open(filename, encoding=encoding) as stream:
-            return self.parse_stream(stream, debug)
+            text = stream.read()
+        return self.parse_string(text, debug)
 
     def parse_string(self, text: str, debug: bool = False) -> NL:
         """Parse a string and return the syntax tree."""
-        tokens = tokenize.generate_tokens(
-            io.StringIO(text).readline, grammar=self.grammar
-        )
+        tokens = tokenize.tokenize(text, grammar=self.grammar)
         return self.parse_tokens(tokens, debug)
 
-    def _partially_consume_prefix(self, prefix: str, column: int) -> Tuple[str, str]:
-        lines: List[str] = []
+    def _partially_consume_prefix(self, prefix: str, column: int) -> tuple[str, str]:
+        lines: list[str] = []
         current_line = ""
         current_column = 0
         wait_for_nl = False

src/blib2to3/pgen2/grammar.py

@@ -16,15 +16,15 @@
 import os
 import pickle
 import tempfile
-from typing import Any, Dict, List, Optional, Tuple, TypeVar, Union
+from typing import Any, Optional, TypeVar, Union
 
 # Local imports
 from . import token
 
 _P = TypeVar("_P", bound="Grammar")
-Label = Tuple[int, Optional[str]]
-DFA = List[List[Tuple[int, int]]]
-DFAS = Tuple[DFA, Dict[int, int]]
+Label = tuple[int, Optional[str]]
+DFA = list[list[tuple[int, int]]]
+DFAS = tuple[DFA, dict[int, int]]
 Path = Union[str, "os.PathLike[str]"]
 
 
@@ -83,16 +83,16 @@ class Grammar:
     """
 
     def __init__(self) -> None:
-        self.symbol2number: Dict[str, int] = {}
-        self.number2symbol: Dict[int, str] = {}
-        self.states: List[DFA] = []
-        self.dfas: Dict[int, DFAS] = {}
-        self.labels: List[Label] = [(0, "EMPTY")]
-        self.keywords: Dict[str, int] = {}
-        self.soft_keywords: Dict[str, int] = {}
-        self.tokens: Dict[int, int] = {}
-        self.symbol2label: Dict[str, int] = {}
-        self.version: Tuple[int, int] = (0, 0)
+        self.symbol2number: dict[str, int] = {}
+        self.number2symbol: dict[int, str] = {}
+        self.states: list[DFA] = []
+        self.dfas: dict[int, DFAS] = {}
+        self.labels: list[Label] = [(0, "EMPTY")]
+        self.keywords: dict[str, int] = {}
+        self.soft_keywords: dict[str, int] = {}
+        self.tokens: dict[int, int] = {}
+        self.symbol2label: dict[str, int] = {}
+        self.version: tuple[int, int] = (0, 0)
         self.start = 256
         # Python 3.7+ parses async as a keyword, not an identifier
         self.async_keywords = False
@@ -114,7 +114,7 @@ def dump(self, filename: Path) -> None:
             pickle.dump(d, f, pickle.HIGHEST_PROTOCOL)
         os.replace(f.name, filename)
 
-    def _update(self, attrs: Dict[str, Any]) -> None:
+    def _update(self, attrs: dict[str, Any]) -> None:
         for k, v in attrs.items():
             setattr(self, k, v)
 
@@ -218,6 +218,7 @@ def report(self) -> None:
 //= DOUBLESLASHEQUAL
 -> RARROW
 := COLONEQUAL
+! BANG
 """
 
 opmap = {}

src/blib2to3/pgen2/literals.py

@@ -4,9 +4,8 @@
 """Safely evaluate Python string literals without using eval()."""
 
 import re
-from typing import Dict, Match
 
-simple_escapes: Dict[str, str] = {
+simple_escapes: dict[str, str] = {
     "a": "\a",
     "b": "\b",
     "f": "\f",
@@ -20,7 +19,7 @@
 }
 
 
-def escape(m: Match[str]) -> str:
+def escape(m: re.Match[str]) -> str:
     all, tail = m.group(0, 1)
     assert all.startswith("\\")
     esc = simple_escapes.get(tail)
@@ -29,16 +28,16 @@ def escape(m: Match[str]) -> str:
     if tail.startswith("x"):
         hexes = tail[1:]
         if len(hexes) < 2:
-            raise ValueError("invalid hex string escape ('\\%s')" % tail)
+            raise ValueError(f"invalid hex string escape ('\\{tail}')")
         try:
             i = int(hexes, 16)
         except ValueError:
-            raise ValueError("invalid hex string escape ('\\%s')" % tail) from None
+            raise ValueError(f"invalid hex string escape ('\\{tail}')") from None
     else:
         try:
             i = int(tail, 8)
         except ValueError:
-            raise ValueError("invalid octal string escape ('\\%s')" % tail) from None
+            raise ValueError(f"invalid octal string escape ('\\{tail}')") from None
     return chr(i)
 
 

src/blib2to3/pgen2/parse.py

@@ -9,20 +9,9 @@
 how this parsing engine works.
 
 """
+from collections.abc import Callable, Iterator
 from contextlib import contextmanager
-from typing import (
-    TYPE_CHECKING,
-    Any,
-    Callable,
-    Dict,
-    Iterator,
-    List,
-    Optional,
-    Set,
-    Tuple,
-    Union,
-    cast,
-)
+from typing import TYPE_CHECKING, Any, Optional, Union, cast
 
 from blib2to3.pgen2.grammar import Grammar
 from blib2to3.pytree import NL, Context, Leaf, Node, RawNode, convert
@@ -34,10 +23,10 @@
     from blib2to3.pgen2.driver import TokenProxy
 
 
-Results = Dict[str, NL]
+Results = dict[str, NL]
 Convert = Callable[[Grammar, RawNode], Union[Node, Leaf]]
-DFA = List[List[Tuple[int, int]]]
-DFAS = Tuple[DFA, Dict[int, int]]
+DFA = list[list[tuple[int, int]]]
+DFAS = tuple[DFA, dict[int, int]]
 
 
 def lam_sub(grammar: Grammar, node: RawNode) -> NL:
@@ -50,24 +39,24 @@ def lam_sub(grammar: Grammar, node: RawNode) -> NL:
 
 
 def stack_copy(
-    stack: List[Tuple[DFAS, int, RawNode]]
-) -> List[Tuple[DFAS, int, RawNode]]:
+    stack: list[tuple[DFAS, int, RawNode]],
+) -> list[tuple[DFAS, int, RawNode]]:
     """Nodeless stack copy."""
     return [(dfa, label, DUMMY_NODE) for dfa, label, _ in stack]
 
 
 class Recorder:
-    def __init__(self, parser: "Parser", ilabels: List[int], context: Context) -> None:
+    def __init__(self, parser: "Parser", ilabels: list[int], context: Context) -> None:
         self.parser = parser
         self._ilabels = ilabels
         self.context = context  # not really matter
 
-        self._dead_ilabels: Set[int] = set()
+        self._dead_ilabels: set[int] = set()
         self._start_point = self.parser.stack
         self._points = {ilabel: stack_copy(self._start_point) for ilabel in ilabels}
 
     @property
-    def ilabels(self) -> Set[int]:
+    def ilabels(self) -> set[int]:
         return self._dead_ilabels.symmetric_difference(self._ilabels)
 
     @contextmanager
@@ -100,18 +89,12 @@ def backtrack(self) -> Iterator[None]:
             self.parser.is_backtracking = is_backtracking
 
     def add_token(self, tok_type: int, tok_val: str, raw: bool = False) -> None:
-        func: Callable[..., Any]
-        if raw:
-            func = self.parser._addtoken
-        else:
-            func = self.parser.addtoken
-
         for ilabel in self.ilabels:
             with self.switch_to(ilabel):
-                args = [tok_type, tok_val, self.context]
                 if raw:
-                    args.insert(0, ilabel)
-                func(*args)
+                    self.parser._addtoken(ilabel, tok_type, tok_val, self.context)
+                else:
+                    self.parser.addtoken(tok_type, tok_val, self.context)
 
     def determine_route(
         self, value: Optional[str] = None, force: bool = False
@@ -233,9 +216,9 @@ def setup(self, proxy: "TokenProxy", start: Optional[int] = None) -> None:
         # where children is a list of nodes or None, and context may be None.
         newnode: RawNode = (start, None, None, [])
         stackentry = (self.grammar.dfas[start], 0, newnode)
-        self.stack: List[Tuple[DFAS, int, RawNode]] = [stackentry]
+        self.stack: list[tuple[DFAS, int, RawNode]] = [stackentry]
         self.rootnode: Optional[NL] = None
-        self.used_names: Set[str] = set()
+        self.used_names: set[str] = set()
         self.proxy = proxy
         self.last_token = None
 
@@ -333,7 +316,7 @@ def _addtoken(self, ilabel: int, type: int, value: str, context: Context) -> boo
                     # No success finding a transition
                     raise ParseError("bad input", type, value, context)
 
-    def classify(self, type: int, value: str, context: Context) -> List[int]:
+    def classify(self, type: int, value: str, context: Context) -> list[int]:
         """Turn a token into a label.  (Internal)
 
         Depending on whether the value is a soft-keyword or not,

src/blib2to3/pgen2/pgen.py

@@ -2,21 +2,11 @@
 # Licensed to PSF under a Contributor Agreement.
 
 import os
-from typing import (
-    IO,
-    Any,
-    Dict,
-    Iterator,
-    List,
-    NoReturn,
-    Optional,
-    Sequence,
-    Tuple,
-    Union,
-)
+from collections.abc import Iterator, Sequence
+from typing import IO, Any, NoReturn, Optional, Union
 
 from blib2to3.pgen2 import grammar, token, tokenize
-from blib2to3.pgen2.tokenize import GoodTokenInfo
+from blib2to3.pgen2.tokenize import TokenInfo
 
 Path = Union[str, "os.PathLike[str]"]
 
@@ -28,8 +18,8 @@ class PgenGrammar(grammar.Grammar):
 class ParserGenerator:
     filename: Path
     stream: IO[str]
-    generator: Iterator[GoodTokenInfo]
-    first: Dict[str, Optional[Dict[str, int]]]
+    generator: Iterator[TokenInfo]
+    first: dict[str, Optional[dict[str, int]]]
 
     def __init__(self, filename: Path, stream: Optional[IO[str]] = None) -> None:
         close_stream = None
@@ -37,8 +27,7 @@ def __init__(self, filename: Path, stream: Optional[IO[str]] = None) -> None:
             stream = open(filename, encoding="utf-8")
             close_stream = stream.close
         self.filename = filename
-        self.stream = stream
-        self.generator = tokenize.generate_tokens(stream.readline)
+        self.generator = tokenize.tokenize(stream.read())
         self.gettoken()  # Initialize lookahead
         self.dfas, self.startsymbol = self.parse()
         if close_stream is not None:
@@ -71,7 +60,7 @@ def make_grammar(self) -> PgenGrammar:
         c.start = c.symbol2number[self.startsymbol]
         return c
 
-    def make_first(self, c: PgenGrammar, name: str) -> Dict[int, int]:
+    def make_first(self, c: PgenGrammar, name: str) -> dict[int, int]:
         rawfirst = self.first[name]
         assert rawfirst is not None
         first = {}
@@ -144,14 +133,14 @@ def calcfirst(self, name: str) -> None:
         dfa = self.dfas[name]
         self.first[name] = None  # dummy to detect left recursion
         state = dfa[0]
-        totalset: Dict[str, int] = {}
+        totalset: dict[str, int] = {}
         overlapcheck = {}
         for label in state.arcs:
             if label in self.dfas:
                 if label in self.first:
                     fset = self.first[label]
                     if fset is None:
-                        raise ValueError("recursion for rule %r" % name)
+                        raise ValueError(f"recursion for rule {name!r}")
                 else:
                     self.calcfirst(label)
                     fset = self.first[label]
@@ -161,18 +150,18 @@ def calcfirst(self, name: str) -> None:
             else:
                 totalset[label] = 1
                 overlapcheck[label] = {label: 1}
-        inverse: Dict[str, str] = {}
+        inverse: dict[str, str] = {}
         for label, itsfirst in overlapcheck.items():
             for symbol in itsfirst:
                 if symbol in inverse:
                     raise ValueError(
-                        "rule %s is ambiguous; %s is in the first sets of %s as well"
-                        " as %s" % (name, symbol, label, inverse[symbol])
+                        f"rule {name} is ambiguous; {symbol} is in the first sets of"
+                        f" {label} as well as {inverse[symbol]}"
                     )
                 inverse[symbol] = label
         self.first[name] = totalset
 
-    def parse(self) -> Tuple[Dict[str, List["DFAState"]], str]:
+    def parse(self) -> tuple[dict[str, list["DFAState"]], str]:
         dfas = {}
         startsymbol: Optional[str] = None
         # MSTART: (NEWLINE | RULE)* ENDMARKER
@@ -197,7 +186,7 @@ def parse(self) -> Tuple[Dict[str, List["DFAState"]], str]:
         assert startsymbol is not None
         return dfas, startsymbol
 
-    def make_dfa(self, start: "NFAState", finish: "NFAState") -> List["DFAState"]:
+    def make_dfa(self, start: "NFAState", finish: "NFAState") -> list["DFAState"]:
         # To turn an NFA into a DFA, we define the states of the DFA
         # to correspond to *sets* of states of the NFA.  Then do some
         # state reduction.  Let's represent sets as dicts with 1 for
@@ -205,12 +194,12 @@ def make_dfa(self, start: "NFAState", finish: "NFAState") -> List["DFAState"]:
         assert isinstance(start, NFAState)
         assert isinstance(finish, NFAState)
 
-        def closure(state: NFAState) -> Dict[NFAState, int]:
-            base: Dict[NFAState, int] = {}
+        def closure(state: NFAState) -> dict[NFAState, int]:
+            base: dict[NFAState, int] = {}
             addclosure(state, base)
             return base
 
-        def addclosure(state: NFAState, base: Dict[NFAState, int]) -> None:
+        def addclosure(state: NFAState, base: dict[NFAState, int]) -> None:
             assert isinstance(state, NFAState)
             if state in base:
                 return
@@ -221,7 +210,7 @@ def addclosure(state: NFAState, base: Dict[NFAState, int]) -> None:
 
         states = [DFAState(closure(start), finish)]
         for state in states:  # NB states grows while we're iterating
-            arcs: Dict[str, Dict[NFAState, int]] = {}
+            arcs: dict[str, dict[NFAState, int]] = {}
             for nfastate in state.nfaset:
                 for label, next in nfastate.arcs:
                     if label is not None:
@@ -248,18 +237,18 @@ def dump_nfa(self, name: str, start: "NFAState", finish: "NFAState") -> None:
                     j = len(todo)
                     todo.append(next)
                 if label is None:
-                    print("    -> %d" % j)
+                    print(f"    -> {j}")
                 else:
-                    print("    %s -> %d" % (label, j))
+                    print(f"    {label} -> {j}")
 
     def dump_dfa(self, name: str, dfa: Sequence["DFAState"]) -> None:
         print("Dump of DFA for", name)
         for i, state in enumerate(dfa):
             print("  State", i, state.isfinal and "(final)" or "")
             for label, next in sorted(state.arcs.items()):
-                print("    %s -> %d" % (label, dfa.index(next)))
+                print(f"    {label} -> {dfa.index(next)}")
 
-    def simplify_dfa(self, dfa: List["DFAState"]) -> None:
+    def simplify_dfa(self, dfa: list["DFAState"]) -> None:
         # This is not theoretically optimal, but works well enough.
         # Algorithm: repeatedly look for two states that have the same
         # set of arcs (same labels pointing to the same nodes) and
@@ -280,7 +269,7 @@ def simplify_dfa(self, dfa: List["DFAState"]) -> None:
                         changes = True
                         break
 
-    def parse_rhs(self) -> Tuple["NFAState", "NFAState"]:
+    def parse_rhs(self) -> tuple["NFAState", "NFAState"]:
         # RHS: ALT ('|' ALT)*
         a, z = self.parse_alt()
         if self.value != "|":
@@ -297,7 +286,7 @@ def parse_rhs(self) -> Tuple["NFAState", "NFAState"]:
                 z.addarc(zz)
             return aa, zz
 
-    def parse_alt(self) -> Tuple["NFAState", "NFAState"]:
+    def parse_alt(self) -> tuple["NFAState", "NFAState"]:
         # ALT: ITEM+
         a, b = self.parse_item()
         while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
@@ -306,7 +295,7 @@ def parse_alt(self) -> Tuple["NFAState", "NFAState"]:
             b = d
         return a, b
 
-    def parse_item(self) -> Tuple["NFAState", "NFAState"]:
+    def parse_item(self) -> tuple["NFAState", "NFAState"]:
         # ITEM: '[' RHS ']' | ATOM ['+' | '*']
         if self.value == "[":
             self.gettoken()
@@ -326,7 +315,7 @@ def parse_item(self) -> Tuple["NFAState", "NFAState"]:
             else:
                 return a, a
 
-    def parse_atom(self) -> Tuple["NFAState", "NFAState"]:
+    def parse_atom(self) -> tuple["NFAState", "NFAState"]:
         # ATOM: '(' RHS ')' | NAME | STRING
         if self.value == "(":
             self.gettoken()
@@ -341,15 +330,12 @@ def parse_atom(self) -> Tuple["NFAState", "NFAState"]:
             return a, z
         else:
             self.raise_error(
-                "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
+                f"expected (...) or NAME or STRING, got {self.type}/{self.value}"
             )
-            raise AssertionError
 
     def expect(self, type: int, value: Optional[Any] = None) -> str:
         if self.type != type or (value is not None and self.value != value):
-            self.raise_error(
-                "expected %s/%s, got %s/%s", type, value, self.type, self.value
-            )
+            self.raise_error(f"expected {type}/{value}, got {self.type}/{self.value}")
         value = self.value
         self.gettoken()
         return value
@@ -361,17 +347,14 @@ def gettoken(self) -> None:
         self.type, self.value, self.begin, self.end, self.line = tup
         # print token.tok_name[self.type], repr(self.value)
 
-    def raise_error(self, msg: str, *args: Any) -> NoReturn:
-        if args:
-            try:
-                msg = msg % args
-            except Exception:
-                msg = " ".join([msg] + list(map(str, args)))
-        raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
+    def raise_error(self, msg: str) -> NoReturn:
+        raise SyntaxError(
+            msg, (str(self.filename), self.end[0], self.end[1], self.line)
+        )
 
 
 class NFAState:
-    arcs: List[Tuple[Optional[str], "NFAState"]]
+    arcs: list[tuple[Optional[str], "NFAState"]]
 
     def __init__(self) -> None:
         self.arcs = []  # list of (label, NFAState) pairs
@@ -383,11 +366,11 @@ def addarc(self, next: "NFAState", label: Optional[str] = None) -> None:
 
 
 class DFAState:
-    nfaset: Dict[NFAState, Any]
+    nfaset: dict[NFAState, Any]
     isfinal: bool
-    arcs: Dict[str, "DFAState"]
+    arcs: dict[str, "DFAState"]
 
-    def __init__(self, nfaset: Dict[NFAState, Any], final: NFAState) -> None:
+    def __init__(self, nfaset: dict[NFAState, Any], final: NFAState) -> None:
         assert isinstance(nfaset, dict)
         assert isinstance(next(iter(nfaset)), NFAState)
         assert isinstance(final, NFAState)

src/blib2to3/pgen2/token.py

@@ -1,6 +1,6 @@
 """Token constants (from "token.h")."""
 
-from typing import Dict, Final
+from typing import Final
 
 #  Taken from Python (r53757) and modified to include some tokens
 #   originally monkeypatched in by pgen2.tokenize
@@ -66,11 +66,15 @@
 ASYNC: Final = 57
 ERRORTOKEN: Final = 58
 COLONEQUAL: Final = 59
-N_TOKENS: Final = 60
+FSTRING_START: Final = 60
+FSTRING_MIDDLE: Final = 61
+FSTRING_END: Final = 62
+BANG: Final = 63
+N_TOKENS: Final = 64
 NT_OFFSET: Final = 256
 # --end constants--
 
-tok_name: Final[Dict[int, str]] = {}
+tok_name: Final[dict[int, str]] = {}
 for _name, _value in list(globals().items()):
     if type(_value) is int:
         tok_name[_value] = _name

src/blib2to3/pgen2/tokenize.py

@@ -28,18 +28,8 @@
 each time a new token is found."""
 
 import sys
-from typing import (
-    Callable,
-    Final,
-    Iterable,
-    Iterator,
-    List,
-    Optional,
-    Pattern,
-    Set,
-    Tuple,
-    Union,
-)
+from collections.abc import Iterator
+from typing import Optional
 
 from blib2to3.pgen2.grammar import Grammar
 from blib2to3.pgen2.token import (
@@ -49,6 +39,9 @@
     DEDENT,
     ENDMARKER,
     ERRORTOKEN,
+    FSTRING_END,
+    FSTRING_MIDDLE,
+    FSTRING_START,
     INDENT,
     NAME,
     NEWLINE,
@@ -62,141 +55,150 @@
 __author__ = "Ka-Ping Yee <ping@lfw.org>"
 __credits__ = "GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, Skip Montanaro"
 
-import re
-from codecs import BOM_UTF8, lookup
+import pytokens
+from pytokens import TokenType
 
-from . import token
+from . import token as _token
 
-__all__ = [x for x in dir(token) if x[0] != "_"] + [
+__all__ = [x for x in dir(_token) if x[0] != "_"] + [
     "tokenize",
     "generate_tokens",
     "untokenize",
 ]
-del token
+del _token
 
+Coord = tuple[int, int]
+TokenInfo = tuple[int, str, Coord, Coord, str]
 
-def group(*choices: str) -> str:
-    return "(" + "|".join(choices) + ")"
-
-
-def any(*choices: str) -> str:
-    return group(*choices) + "*"
-
-
-def maybe(*choices: str) -> str:
-    return group(*choices) + "?"
-
-
-def _combinations(*l: str) -> Set[str]:
-    return {x + y for x in l for y in l + ("",) if x.casefold() != y.casefold()}
-
-
-Whitespace = r"[ \f\t]*"
-Comment = r"#[^\r\n]*"
-Ignore = Whitespace + any(r"\\\r?\n" + Whitespace) + maybe(Comment)
-Name = (  # this is invalid but it's fine because Name comes after Number in all groups
-    r"[^\s#\(\)\[\]\{\}+\-*/!@$%^&=|;:'\",\.<>/?`~\\]+"
-)
-
-Binnumber = r"0[bB]_?[01]+(?:_[01]+)*"
-Hexnumber = r"0[xX]_?[\da-fA-F]+(?:_[\da-fA-F]+)*[lL]?"
-Octnumber = r"0[oO]?_?[0-7]+(?:_[0-7]+)*[lL]?"
-Decnumber = group(r"[1-9]\d*(?:_\d+)*[lL]?", "0[lL]?")
-Intnumber = group(Binnumber, Hexnumber, Octnumber, Decnumber)
-Exponent = r"[eE][-+]?\d+(?:_\d+)*"
-Pointfloat = group(r"\d+(?:_\d+)*\.(?:\d+(?:_\d+)*)?", r"\.\d+(?:_\d+)*") + maybe(
-    Exponent
-)
-Expfloat = r"\d+(?:_\d+)*" + Exponent
-Floatnumber = group(Pointfloat, Expfloat)
-Imagnumber = group(r"\d+(?:_\d+)*[jJ]", Floatnumber + r"[jJ]")
-Number = group(Imagnumber, Floatnumber, Intnumber)
-
-# Tail end of ' string.
-Single = r"[^'\\]*(?:\\.[^'\\]*)*'"
-# Tail end of " string.
-Double = r'[^"\\]*(?:\\.[^"\\]*)*"'
-# Tail end of ''' string.
-Single3 = r"[^'\\]*(?:(?:\\.|'(?!''))[^'\\]*)*'''"
-# Tail end of """ string.
-Double3 = r'[^"\\]*(?:(?:\\.|"(?!""))[^"\\]*)*"""'
-_litprefix = r"(?:[uUrRbBfF]|[rR][fFbB]|[fFbBuU][rR])?"
-Triple = group(_litprefix + "'''", _litprefix + '"""')
-# Single-line ' or " string.
-String = group(
-    _litprefix + r"'[^\n'\\]*(?:\\.[^\n'\\]*)*'",
-    _litprefix + r'"[^\n"\\]*(?:\\.[^\n"\\]*)*"',
-)
-
-# Because of leftmost-then-longest match semantics, be sure to put the
-# longest operators first (e.g., if = came before ==, == would get
-# recognized as two instances of =).
-Operator = group(
-    r"\*\*=?",
-    r">>=?",
-    r"<<=?",
-    r"<>",
-    r"!=",
-    r"//=?",
-    r"->",
-    r"[+\-*/%&@|^=<>:]=?",
-    r"~",
-)
-
-Bracket = "[][(){}]"
-Special = group(r"\r?\n", r"[:;.,`@]")
-Funny = group(Operator, Bracket, Special)
-
-# First (or only) line of ' or " string.
-ContStr = group(
-    _litprefix + r"'[^\n'\\]*(?:\\.[^\n'\\]*)*" + group("'", r"\\\r?\n"),
-    _litprefix + r'"[^\n"\\]*(?:\\.[^\n"\\]*)*' + group('"', r"\\\r?\n"),
-)
-PseudoExtras = group(r"\\\r?\n", Comment, Triple)
-PseudoToken = Whitespace + group(PseudoExtras, Number, Funny, ContStr, Name)
-
-pseudoprog: Final = re.compile(PseudoToken, re.UNICODE)
-single3prog = re.compile(Single3)
-double3prog = re.compile(Double3)
-
-_strprefixes = (
-    _combinations("r", "R", "f", "F")
-    | _combinations("r", "R", "b", "B")
-    | {"u", "U", "ur", "uR", "Ur", "UR"}
-)
-
-endprogs: Final = {
-    "'": re.compile(Single),
-    '"': re.compile(Double),
-    "'''": single3prog,
-    '"""': double3prog,
-    **{f"{prefix}'''": single3prog for prefix in _strprefixes},
-    **{f'{prefix}"""': double3prog for prefix in _strprefixes},
+TOKEN_TYPE_MAP = {
+    TokenType.indent: INDENT,
+    TokenType.dedent: DEDENT,
+    TokenType.newline: NEWLINE,
+    TokenType.nl: NL,
+    TokenType.comment: COMMENT,
+    TokenType.semicolon: OP,
+    TokenType.lparen: OP,
+    TokenType.rparen: OP,
+    TokenType.lbracket: OP,
+    TokenType.rbracket: OP,
+    TokenType.lbrace: OP,
+    TokenType.rbrace: OP,
+    TokenType.colon: OP,
+    TokenType.op: OP,
+    TokenType.identifier: NAME,
+    TokenType.number: NUMBER,
+    TokenType.string: STRING,
+    TokenType.fstring_start: FSTRING_START,
+    TokenType.fstring_middle: FSTRING_MIDDLE,
+    TokenType.fstring_end: FSTRING_END,
+    TokenType.endmarker: ENDMARKER,
 }
 
-triple_quoted: Final = (
-    {"'''", '"""'}
-    | {f"{prefix}'''" for prefix in _strprefixes}
-    | {f'{prefix}"""' for prefix in _strprefixes}
-)
-single_quoted: Final = (
-    {"'", '"'}
-    | {f"{prefix}'" for prefix in _strprefixes}
-    | {f'{prefix}"' for prefix in _strprefixes}
-)
 
-tabsize = 8
+class TokenError(Exception): ...
 
 
-class TokenError(Exception):
-    pass
+def transform_whitespace(
+    token: pytokens.Token, source: str, prev_token: Optional[pytokens.Token]
+) -> pytokens.Token:
+    r"""
+    Black treats `\\\n` at the end of a line as a 'NL' token, while it
+    is ignored as whitespace in the regular Python parser.
+    But, only the first one. If there's a `\\\n` following it
+    (as in, a \ just by itself on a line), that is not made into NL.
+    """
+    if (
+        token.type == TokenType.whitespace
+        and prev_token is not None
+        and prev_token.type not in (TokenType.nl, TokenType.newline)
+    ):
+        token_str = source[token.start_index : token.end_index]
+        if token_str.startswith("\\\r\n"):
+            return pytokens.Token(
+                TokenType.nl,
+                token.start_index,
+                token.start_index + 3,
+                token.start_line,
+                token.start_col,
+                token.start_line,
+                token.start_col + 3,
+            )
+        elif token_str.startswith("\\\n") or token_str.startswith("\\\r"):
+            return pytokens.Token(
+                TokenType.nl,
+                token.start_index,
+                token.start_index + 2,
+                token.start_line,
+                token.start_col,
+                token.start_line,
+                token.start_col + 2,
+            )
+
+    return token
 
 
-class StopTokenizing(Exception):
-    pass
+def tokenize(source: str, grammar: Optional[Grammar] = None) -> Iterator[TokenInfo]:
+    lines = source.split("\n")
+    lines += [""]  # For newline tokens in files that don't end in a newline
+    line, column = 1, 0
 
+    prev_token: Optional[pytokens.Token] = None
+    try:
+        for token in pytokens.tokenize(source):
+            token = transform_whitespace(token, source, prev_token)
 
-Coord = Tuple[int, int]
+            line, column = token.start_line, token.start_col
+            if token.type == TokenType.whitespace:
+                continue
+
+            token_str = source[token.start_index : token.end_index]
+
+            if token.type == TokenType.newline and token_str == "":
+                # Black doesn't yield empty newline tokens at the end of a file
+                # if there's no newline at the end of a file.
+                prev_token = token
+                continue
+
+            source_line = lines[token.start_line - 1]
+
+            if token.type == TokenType.identifier and token_str in ("async", "await"):
+                # Black uses `async` and `await` token types just for those two keywords
+                yield (
+                    ASYNC if token_str == "async" else AWAIT,
+                    token_str,
+                    (token.start_line, token.start_col),
+                    (token.end_line, token.end_col),
+                    source_line,
+                )
+            elif token.type == TokenType.op and token_str == "...":
+                # Black doesn't have an ellipsis token yet, yield 3 DOTs instead
+                assert token.start_line == token.end_line
+                assert token.end_col == token.start_col + 3
+
+                token_str = "."
+                for start_col in range(token.start_col, token.start_col + 3):
+                    end_col = start_col + 1
+                    yield (
+                        TOKEN_TYPE_MAP[token.type],
+                        token_str,
+                        (token.start_line, start_col),
+                        (token.end_line, end_col),
+                        source_line,
+                    )
+            else:
+                yield (
+                    TOKEN_TYPE_MAP[token.type],
+                    token_str,
+                    (token.start_line, token.start_col),
+                    (token.end_line, token.end_col),
+                    source_line,
+                )
+            prev_token = token
+
+    except pytokens.UnexpectedEOF:
+        raise TokenError("Unexpected EOF in multi-line statement", (line, column))
+    except pytokens.TokenizeError as exc:
+        raise TokenError(f"Failed to parse: {type(exc).__name__}", (line, column))
 
 
 def printtoken(
@@ -204,495 +206,14 @@ def printtoken(
 ) -> None:  # for testing
     (srow, scol) = srow_col
     (erow, ecol) = erow_col
-    print(
-        "%d,%d-%d,%d:\t%s\t%s" % (srow, scol, erow, ecol, tok_name[type], repr(token))
-    )
-
-
-TokenEater = Callable[[int, str, Coord, Coord, str], None]
-
-
-def tokenize(readline: Callable[[], str], tokeneater: TokenEater = printtoken) -> None:
-    """
-    The tokenize() function accepts two parameters: one representing the
-    input stream, and one providing an output mechanism for tokenize().
-
-    The first parameter, readline, must be a callable object which provides
-    the same interface as the readline() method of built-in file objects.
-    Each call to the function should return one line of input as a string.
-
-    The second parameter, tokeneater, must also be a callable object. It is
-    called once for each token, with five arguments, corresponding to the
-    tuples generated by generate_tokens().
-    """
-    try:
-        tokenize_loop(readline, tokeneater)
-    except StopTokenizing:
-        pass
-
-
-# backwards compatible interface
-def tokenize_loop(readline: Callable[[], str], tokeneater: TokenEater) -> None:
-    for token_info in generate_tokens(readline):
-        tokeneater(*token_info)
-
-
-GoodTokenInfo = Tuple[int, str, Coord, Coord, str]
-TokenInfo = Union[Tuple[int, str], GoodTokenInfo]
-
-
-class Untokenizer:
-    tokens: List[str]
-    prev_row: int
-    prev_col: int
-
-    def __init__(self) -> None:
-        self.tokens = []
-        self.prev_row = 1
-        self.prev_col = 0
-
-    def add_whitespace(self, start: Coord) -> None:
-        row, col = start
-        assert row <= self.prev_row
-        col_offset = col - self.prev_col
-        if col_offset:
-            self.tokens.append(" " * col_offset)
-
-    def untokenize(self, iterable: Iterable[TokenInfo]) -> str:
-        for t in iterable:
-            if len(t) == 2:
-                self.compat(t, iterable)
-                break
-            tok_type, token, start, end, line = t
-            self.add_whitespace(start)
-            self.tokens.append(token)
-            self.prev_row, self.prev_col = end
-            if tok_type in (NEWLINE, NL):
-                self.prev_row += 1
-                self.prev_col = 0
-        return "".join(self.tokens)
-
-    def compat(self, token: Tuple[int, str], iterable: Iterable[TokenInfo]) -> None:
-        startline = False
-        indents = []
-        toks_append = self.tokens.append
-        toknum, tokval = token
-        if toknum in (NAME, NUMBER):
-            tokval += " "
-        if toknum in (NEWLINE, NL):
-            startline = True
-        for tok in iterable:
-            toknum, tokval = tok[:2]
-
-            if toknum in (NAME, NUMBER, ASYNC, AWAIT):
-                tokval += " "
-
-            if toknum == INDENT:
-                indents.append(tokval)
-                continue
-            elif toknum == DEDENT:
-                indents.pop()
-                continue
-            elif toknum in (NEWLINE, NL):
-                startline = True
-            elif startline and indents:
-                toks_append(indents[-1])
-                startline = False
-            toks_append(tokval)
-
-
-cookie_re = re.compile(r"^[ \t\f]*#.*?coding[:=][ \t]*([-\w.]+)", re.ASCII)
-blank_re = re.compile(rb"^[ \t\f]*(?:[#\r\n]|$)", re.ASCII)
-
-
-def _get_normal_name(orig_enc: str) -> str:
-    """Imitates get_normal_name in tokenizer.c."""
-    # Only care about the first 12 characters.
-    enc = orig_enc[:12].lower().replace("_", "-")
-    if enc == "utf-8" or enc.startswith("utf-8-"):
-        return "utf-8"
-    if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or enc.startswith(
-        ("latin-1-", "iso-8859-1-", "iso-latin-1-")
-    ):
-        return "iso-8859-1"
-    return orig_enc
-
-
-def detect_encoding(readline: Callable[[], bytes]) -> Tuple[str, List[bytes]]:
-    """
-    The detect_encoding() function is used to detect the encoding that should
-    be used to decode a Python source file. It requires one argument, readline,
-    in the same way as the tokenize() generator.
-
-    It will call readline a maximum of twice, and return the encoding used
-    (as a string) and a list of any lines (left as bytes) it has read
-    in.
-
-    It detects the encoding from the presence of a utf-8 bom or an encoding
-    cookie as specified in pep-0263. If both a bom and a cookie are present, but
-    disagree, a SyntaxError will be raised. If the encoding cookie is an invalid
-    charset, raise a SyntaxError.  Note that if a utf-8 bom is found,
-    'utf-8-sig' is returned.
-
-    If no encoding is specified, then the default of 'utf-8' will be returned.
-    """
-    bom_found = False
-    encoding = None
-    default = "utf-8"
-
-    def read_or_stop() -> bytes:
-        try:
-            return readline()
-        except StopIteration:
-            return b""
-
-    def find_cookie(line: bytes) -> Optional[str]:
-        try:
-            line_string = line.decode("ascii")
-        except UnicodeDecodeError:
-            return None
-        match = cookie_re.match(line_string)
-        if not match:
-            return None
-        encoding = _get_normal_name(match.group(1))
-        try:
-            codec = lookup(encoding)
-        except LookupError:
-            # This behaviour mimics the Python interpreter
-            raise SyntaxError("unknown encoding: " + encoding)
-
-        if bom_found:
-            if codec.name != "utf-8":
-                # This behaviour mimics the Python interpreter
-                raise SyntaxError("encoding problem: utf-8")
-            encoding += "-sig"
-        return encoding
-
-    first = read_or_stop()
-    if first.startswith(BOM_UTF8):
-        bom_found = True
-        first = first[3:]
-        default = "utf-8-sig"
-    if not first:
-        return default, []
-
-    encoding = find_cookie(first)
-    if encoding:
-        return encoding, [first]
-    if not blank_re.match(first):
-        return default, [first]
-
-    second = read_or_stop()
-    if not second:
-        return default, [first]
-
-    encoding = find_cookie(second)
-    if encoding:
-        return encoding, [first, second]
-
-    return default, [first, second]
-
-
-def untokenize(iterable: Iterable[TokenInfo]) -> str:
-    """Transform tokens back into Python source code.
-
-    Each element returned by the iterable must be a token sequence
-    with at least two elements, a token number and token value.  If
-    only two tokens are passed, the resulting output is poor.
-
-    Round-trip invariant for full input:
-        Untokenized source will match input source exactly
-
-    Round-trip invariant for limited input:
-        # Output text will tokenize the back to the input
-        t1 = [tok[:2] for tok in generate_tokens(f.readline)]
-        newcode = untokenize(t1)
-        readline = iter(newcode.splitlines(1)).next
-        t2 = [tok[:2] for tokin generate_tokens(readline)]
-        assert t1 == t2
-    """
-    ut = Untokenizer()
-    return ut.untokenize(iterable)
-
-
-def generate_tokens(
-    readline: Callable[[], str], grammar: Optional[Grammar] = None
-) -> Iterator[GoodTokenInfo]:
-    """
-    The generate_tokens() generator requires one argument, readline, which
-    must be a callable object which provides the same interface as the
-    readline() method of built-in file objects. Each call to the function
-    should return one line of input as a string.  Alternately, readline
-    can be a callable function terminating with StopIteration:
-        readline = open(myfile).next    # Example of alternate readline
-
-    The generator produces 5-tuples with these members: the token type; the
-    token string; a 2-tuple (srow, scol) of ints specifying the row and
-    column where the token begins in the source; a 2-tuple (erow, ecol) of
-    ints specifying the row and column where the token ends in the source;
-    and the line on which the token was found. The line passed is the
-    logical line; continuation lines are included.
-    """
-    lnum = parenlev = continued = 0
-    numchars: Final[str] = "0123456789"
-    contstr, needcont = "", 0
-    contline: Optional[str] = None
-    indents = [0]
-
-    # If we know we're parsing 3.7+, we can unconditionally parse `async` and
-    # `await` as keywords.
-    async_keywords = False if grammar is None else grammar.async_keywords
-    # 'stashed' and 'async_*' are used for async/await parsing
-    stashed: Optional[GoodTokenInfo] = None
-    async_def = False
-    async_def_indent = 0
-    async_def_nl = False
-
-    strstart: Tuple[int, int]
-    endprog: Pattern[str]
-
-    while 1:  # loop over lines in stream
-        try:
-            line = readline()
-        except StopIteration:
-            line = ""
-        lnum += 1
-        pos, max = 0, len(line)
-
-        if contstr:  # continued string
-            assert contline is not None
-            if not line:
-                raise TokenError("EOF in multi-line string", strstart)
-            endmatch = endprog.match(line)
-            if endmatch:
-                pos = end = endmatch.end(0)
-                yield (
-                    STRING,
-                    contstr + line[:end],
-                    strstart,
-                    (lnum, end),
-                    contline + line,
-                )
-                contstr, needcont = "", 0
-                contline = None
-            elif needcont and line[-2:] != "\\\n" and line[-3:] != "\\\r\n":
-                yield (
-                    ERRORTOKEN,
-                    contstr + line,
-                    strstart,
-                    (lnum, len(line)),
-                    contline,
-                )
-                contstr = ""
-                contline = None
-                continue
-            else:
-                contstr = contstr + line
-                contline = contline + line
-                continue
-
-        elif parenlev == 0 and not continued:  # new statement
-            if not line:
-                break
-            column = 0
-            while pos < max:  # measure leading whitespace
-                if line[pos] == " ":
-                    column += 1
-                elif line[pos] == "\t":
-                    column = (column // tabsize + 1) * tabsize
-                elif line[pos] == "\f":
-                    column = 0
-                else:
-                    break
-                pos += 1
-            if pos == max:
-                break
-
-            if stashed:
-                yield stashed
-                stashed = None
-
-            if line[pos] in "\r\n":  # skip blank lines
-                yield (NL, line[pos:], (lnum, pos), (lnum, len(line)), line)
-                continue
-
-            if line[pos] == "#":  # skip comments
-                comment_token = line[pos:].rstrip("\r\n")
-                nl_pos = pos + len(comment_token)
-                yield (
-                    COMMENT,
-                    comment_token,
-                    (lnum, pos),
-                    (lnum, nl_pos),
-                    line,
-                )
-                yield (NL, line[nl_pos:], (lnum, nl_pos), (lnum, len(line)), line)
-                continue
-
-            if column > indents[-1]:  # count indents
-                indents.append(column)
-                yield (INDENT, line[:pos], (lnum, 0), (lnum, pos), line)
-
-            while column < indents[-1]:  # count dedents
-                if column not in indents:
-                    raise IndentationError(
-                        "unindent does not match any outer indentation level",
-                        ("<tokenize>", lnum, pos, line),
-                    )
-                indents = indents[:-1]
-
-                if async_def and async_def_indent >= indents[-1]:
-                    async_def = False
-                    async_def_nl = False
-                    async_def_indent = 0
-
-                yield (DEDENT, "", (lnum, pos), (lnum, pos), line)
-
-            if async_def and async_def_nl and async_def_indent >= indents[-1]:
-                async_def = False
-                async_def_nl = False
-                async_def_indent = 0
-
-        else:  # continued statement
-            if not line:
-                raise TokenError("EOF in multi-line statement", (lnum, 0))
-            continued = 0
-
-        while pos < max:
-            pseudomatch = pseudoprog.match(line, pos)
-            if pseudomatch:  # scan for tokens
-                start, end = pseudomatch.span(1)
-                spos, epos, pos = (lnum, start), (lnum, end), end
-                token, initial = line[start:end], line[start]
-
-                if initial in numchars or (
-                    initial == "." and token != "."
-                ):  # ordinary number
-                    yield (NUMBER, token, spos, epos, line)
-                elif initial in "\r\n":
-                    newline = NEWLINE
-                    if parenlev > 0:
-                        newline = NL
-                    elif async_def:
-                        async_def_nl = True
-                    if stashed:
-                        yield stashed
-                        stashed = None
-                    yield (newline, token, spos, epos, line)
-
-                elif initial == "#":
-                    assert not token.endswith("\n")
-                    if stashed:
-                        yield stashed
-                        stashed = None
-                    yield (COMMENT, token, spos, epos, line)
-                elif token in triple_quoted:
-                    endprog = endprogs[token]
-                    endmatch = endprog.match(line, pos)
-                    if endmatch:  # all on one line
-                        pos = endmatch.end(0)
-                        token = line[start:pos]
-                        if stashed:
-                            yield stashed
-                            stashed = None
-                        yield (STRING, token, spos, (lnum, pos), line)
-                    else:
-                        strstart = (lnum, start)  # multiple lines
-                        contstr = line[start:]
-                        contline = line
-                        break
-                elif (
-                    initial in single_quoted
-                    or token[:2] in single_quoted
-                    or token[:3] in single_quoted
-                ):
-                    if token[-1] == "\n":  # continued string
-                        strstart = (lnum, start)
-                        maybe_endprog = (
-                            endprogs.get(initial)
-                            or endprogs.get(token[1])
-                            or endprogs.get(token[2])
-                        )
-                        assert (
-                            maybe_endprog is not None
-                        ), f"endprog not found for {token}"
-                        endprog = maybe_endprog
-                        contstr, needcont = line[start:], 1
-                        contline = line
-                        break
-                    else:  # ordinary string
-                        if stashed:
-                            yield stashed
-                            stashed = None
-                        yield (STRING, token, spos, epos, line)
-                elif initial.isidentifier():  # ordinary name
-                    if token in ("async", "await"):
-                        if async_keywords or async_def:
-                            yield (
-                                ASYNC if token == "async" else AWAIT,
-                                token,
-                                spos,
-                                epos,
-                                line,
-                            )
-                            continue
-
-                    tok = (NAME, token, spos, epos, line)
-                    if token == "async" and not stashed:
-                        stashed = tok
-                        continue
-
-                    if token in ("def", "for"):
-                        if stashed and stashed[0] == NAME and stashed[1] == "async":
-                            if token == "def":
-                                async_def = True
-                                async_def_indent = indents[-1]
-
-                            yield (
-                                ASYNC,
-                                stashed[1],
-                                stashed[2],
-                                stashed[3],
-                                stashed[4],
-                            )
-                            stashed = None
-
-                    if stashed:
-                        yield stashed
-                        stashed = None
-
-                    yield tok
-                elif initial == "\\":  # continued stmt
-                    # This yield is new; needed for better idempotency:
-                    if stashed:
-                        yield stashed
-                        stashed = None
-                    yield (NL, token, spos, (lnum, pos), line)
-                    continued = 1
-                else:
-                    if initial in "([{":
-                        parenlev += 1
-                    elif initial in ")]}":
-                        parenlev -= 1
-                    if stashed:
-                        yield stashed
-                        stashed = None
-                    yield (OP, token, spos, epos, line)
-            else:
-                yield (ERRORTOKEN, line[pos], (lnum, pos), (lnum, pos + 1), line)
-                pos += 1
-
-    if stashed:
-        yield stashed
-        stashed = None
-
-    for _indent in indents[1:]:  # pop remaining indent levels
-        yield (DEDENT, "", (lnum, 0), (lnum, 0), "")
-    yield (ENDMARKER, "", (lnum, 0), (lnum, 0), "")
+    print(f"{srow},{scol}-{erow},{ecol}:\t{tok_name[type]}\t{token!r}")
 
 
 if __name__ == "__main__":  # testing
     if len(sys.argv) > 1:
-        tokenize(open(sys.argv[1]).readline)
+        token_iterator = tokenize(open(sys.argv[1]).read())
     else:
-        tokenize(sys.stdin.readline)
+        token_iterator = tokenize(sys.stdin.read())
+
+    for tok in token_iterator:
+        printtoken(*tok)

src/blib2to3/pygram.py

@@ -70,6 +70,10 @@ class _python_symbols(Symbols):
     file_input: int
     flow_stmt: int
     for_stmt: int
+    fstring: int
+    fstring_format_spec: int
+    fstring_middle: int
+    fstring_replacement_field: int
     funcdef: int
     global_stmt: int
     guard: int

src/blib2to3/pytree.py

@@ -12,18 +12,8 @@
 
 # mypy: allow-untyped-defs, allow-incomplete-defs
 
-from typing import (
-    Any,
-    Dict,
-    Iterable,
-    Iterator,
-    List,
-    Optional,
-    Set,
-    Tuple,
-    TypeVar,
-    Union,
-)
+from collections.abc import Iterable, Iterator
+from typing import Any, Optional, TypeVar, Union
 
 from blib2to3.pgen2.grammar import Grammar
 
@@ -34,18 +24,21 @@
 
 HUGE: int = 0x7FFFFFFF  # maximum repeat count, default max
 
-_type_reprs: Dict[int, Union[str, int]] = {}
+_type_reprs: dict[int, Union[str, int]] = {}
 
 
 def type_repr(type_num: int) -> Union[str, int]:
     global _type_reprs
     if not _type_reprs:
-        from .pygram import python_symbols
+        from . import pygram
+
+        if not hasattr(pygram, "python_symbols"):
+            pygram.initialize(cache_dir=None)
 
         # printing tokens is possible but not as useful
         # from .pgen2 import token // token.__dict__.items():
-        for name in dir(python_symbols):
-            val = getattr(python_symbols, name)
+        for name in dir(pygram.python_symbols):
+            val = getattr(pygram.python_symbols, name)
             if type(val) == int:
                 _type_reprs[val] = name
     return _type_reprs.setdefault(type_num, type_num)
@@ -54,8 +47,8 @@ def type_repr(type_num: int) -> Union[str, int]:
 _P = TypeVar("_P", bound="Base")
 
 NL = Union["Node", "Leaf"]
-Context = Tuple[str, Tuple[int, int]]
-RawNode = Tuple[int, Optional[str], Optional[Context], Optional[List[NL]]]
+Context = tuple[str, tuple[int, int]]
+RawNode = tuple[int, Optional[str], Optional[Context], Optional[list[NL]]]
 
 
 class Base:
@@ -71,7 +64,7 @@ class Base:
     # Default values for instance variables
     type: int  # int: token number (< 256) or symbol number (>= 256)
     parent: Optional["Node"] = None  # Parent node pointer, or None
-    children: List[NL]  # List of subnodes
+    children: list[NL]  # List of subnodes
     was_changed: bool = False
     was_checked: bool = False
 
@@ -132,7 +125,7 @@ def pre_order(self) -> Iterator[NL]:
         """
         raise NotImplementedError
 
-    def replace(self, new: Union[NL, List[NL]]) -> None:
+    def replace(self, new: Union[NL, list[NL]]) -> None:
         """Replace this node with a new one in the parent."""
         assert self.parent is not None, str(self)
         assert new is not None
@@ -239,16 +232,16 @@ def get_suffix(self) -> str:
 class Node(Base):
     """Concrete implementation for interior nodes."""
 
-    fixers_applied: Optional[List[Any]]
-    used_names: Optional[Set[str]]
+    fixers_applied: Optional[list[Any]]
+    used_names: Optional[set[str]]
 
     def __init__(
         self,
         type: int,
-        children: List[NL],
+        children: list[NL],
         context: Optional[Any] = None,
         prefix: Optional[str] = None,
-        fixers_applied: Optional[List[Any]] = None,
+        fixers_applied: Optional[list[Any]] = None,
     ) -> None:
         """
         Initializer.
@@ -275,11 +268,7 @@ def __init__(
     def __repr__(self) -> str:
         """Return a canonical string representation."""
         assert self.type is not None
-        return "{}({}, {!r})".format(
-            self.__class__.__name__,
-            type_repr(self.type),
-            self.children,
-        )
+        return f"{self.__class__.__name__}({type_repr(self.type)}, {self.children!r})"
 
     def __str__(self) -> str:
         """
@@ -360,12 +349,12 @@ def append_child(self, child: NL) -> None:
         self.invalidate_sibling_maps()
 
     def invalidate_sibling_maps(self) -> None:
-        self.prev_sibling_map: Optional[Dict[int, Optional[NL]]] = None
-        self.next_sibling_map: Optional[Dict[int, Optional[NL]]] = None
+        self.prev_sibling_map: Optional[dict[int, Optional[NL]]] = None
+        self.next_sibling_map: Optional[dict[int, Optional[NL]]] = None
 
     def update_sibling_maps(self) -> None:
-        _prev: Dict[int, Optional[NL]] = {}
-        _next: Dict[int, Optional[NL]] = {}
+        _prev: dict[int, Optional[NL]] = {}
+        _next: dict[int, Optional[NL]] = {}
         self.prev_sibling_map = _prev
         self.next_sibling_map = _next
         previous: Optional[NL] = None
@@ -381,11 +370,11 @@ class Leaf(Base):
 
     # Default values for instance variables
     value: str
-    fixers_applied: List[Any]
+    fixers_applied: list[Any]
     bracket_depth: int
     # Changed later in brackets.py
     opening_bracket: Optional["Leaf"] = None
-    used_names: Optional[Set[str]]
+    used_names: Optional[set[str]]
     _prefix = ""  # Whitespace and comments preceding this token in the input
     lineno: int = 0  # Line where this token starts in the input
     column: int = 0  # Column where this token starts in the input
@@ -400,7 +389,7 @@ def __init__(
         value: str,
         context: Optional[Context] = None,
         prefix: Optional[str] = None,
-        fixers_applied: List[Any] = [],
+        fixers_applied: list[Any] = [],
         opening_bracket: Optional["Leaf"] = None,
         fmt_pass_converted_first_leaf: Optional["Leaf"] = None,
     ) -> None:
@@ -418,7 +407,7 @@ def __init__(
         self.value = value
         if prefix is not None:
             self._prefix = prefix
-        self.fixers_applied: Optional[List[Any]] = fixers_applied[:]
+        self.fixers_applied: Optional[list[Any]] = fixers_applied[:]
         self.children = []
         self.opening_bracket = opening_bracket
         self.fmt_pass_converted_first_leaf = fmt_pass_converted_first_leaf
@@ -428,10 +417,9 @@ def __repr__(self) -> str:
         from .pgen2.token import tok_name
 
         assert self.type is not None
-        return "{}({}, {!r})".format(
-            self.__class__.__name__,
-            tok_name.get(self.type, self.type),
-            self.value,
+        return (
+            f"{self.__class__.__name__}({tok_name.get(self.type, self.type)},"
+            f" {self.value!r})"
         )
 
     def __str__(self) -> str:
@@ -500,7 +488,7 @@ def convert(gr: Grammar, raw_node: RawNode) -> NL:
         return Leaf(type, value or "", context=context)
 
 
-_Results = Dict[str, NL]
+_Results = dict[str, NL]
 
 
 class BasePattern:
@@ -534,7 +522,7 @@ def __repr__(self) -> str:
         args = [type_repr(self.type), self.content, self.name]
         while args and args[-1] is None:
             del args[-1]
-        return "{}({})".format(self.__class__.__name__, ", ".join(map(repr, args)))
+        return f"{self.__class__.__name__}({', '.join(map(repr, args))})"
 
     def _submatch(self, node, results=None) -> bool:
         raise NotImplementedError
@@ -573,7 +561,7 @@ def match(self, node: NL, results: Optional[_Results] = None) -> bool:
             results[self.name] = node
         return True
 
-    def match_seq(self, nodes: List[NL], results: Optional[_Results] = None) -> bool:
+    def match_seq(self, nodes: list[NL], results: Optional[_Results] = None) -> bool:
         """
         Does this pattern exactly match a sequence of nodes?
 
@@ -583,7 +571,7 @@ def match_seq(self, nodes: List[NL], results: Optional[_Results] = None) -> bool
             return False
         return self.match(nodes[0], results)
 
-    def generate_matches(self, nodes: List[NL]) -> Iterator[Tuple[int, _Results]]:
+    def generate_matches(self, nodes: list[NL]) -> Iterator[tuple[int, _Results]]:
         """
         Generator yielding all matches for this pattern.
 
@@ -813,7 +801,7 @@ def match_seq(self, nodes, results=None) -> bool:
                 return True
         return False
 
-    def generate_matches(self, nodes) -> Iterator[Tuple[int, _Results]]:
+    def generate_matches(self, nodes) -> Iterator[tuple[int, _Results]]:
         """
         Generator yielding matches for a sequence of nodes.
 
@@ -858,7 +846,7 @@ def generate_matches(self, nodes) -> Iterator[Tuple[int, _Results]]:
                 if hasattr(sys, "getrefcount"):
                     sys.stderr = save_stderr
 
-    def _iterative_matches(self, nodes) -> Iterator[Tuple[int, _Results]]:
+    def _iterative_matches(self, nodes) -> Iterator[tuple[int, _Results]]:
         """Helper to iteratively yield the matches."""
         nodelen = len(nodes)
         if 0 >= self.min:
@@ -887,7 +875,7 @@ def _iterative_matches(self, nodes) -> Iterator[Tuple[int, _Results]]:
                                 new_results.append((c0 + c1, r))
             results = new_results
 
-    def _bare_name_matches(self, nodes) -> Tuple[int, _Results]:
+    def _bare_name_matches(self, nodes) -> tuple[int, _Results]:
         """Special optimized matcher for bare_name."""
         count = 0
         r = {}  # type: _Results
@@ -904,7 +892,7 @@ def _bare_name_matches(self, nodes) -> Tuple[int, _Results]:
         r[self.name] = nodes[:count]
         return count, r
 
-    def _recursive_matches(self, nodes, count) -> Iterator[Tuple[int, _Results]]:
+    def _recursive_matches(self, nodes, count) -> Iterator[tuple[int, _Results]]:
         """Helper to recursively yield the matches."""
         assert self.content is not None
         if count >= self.min:
@@ -941,7 +929,7 @@ def match_seq(self, nodes, results=None) -> bool:
         # We only match an empty sequence of nodes in its entirety
         return len(nodes) == 0
 
-    def generate_matches(self, nodes: List[NL]) -> Iterator[Tuple[int, _Results]]:
+    def generate_matches(self, nodes: list[NL]) -> Iterator[tuple[int, _Results]]:
         if self.content is None:
             # Return a match if there is an empty sequence
             if len(nodes) == 0:
@@ -954,8 +942,8 @@ def generate_matches(self, nodes: List[NL]) -> Iterator[Tuple[int, _Results]]:
 
 
 def generate_matches(
-    patterns: List[BasePattern], nodes: List[NL]
-) -> Iterator[Tuple[int, _Results]]:
+    patterns: list[BasePattern], nodes: list[NL]
+) -> Iterator[tuple[int, _Results]]:
     """
     Generator yielding matches for a sequence of patterns and nodes.
 

tests/data/cases/allow_empty_first_line.py

@@ -1,4 +1,3 @@
-# flags: --preview
 def foo():
     """
     Docstring
@@ -62,6 +61,26 @@ def method(self):
 
         pass
 
+
+async def async_fn():
+
+    """Docstring."""
+
+
+@decorated
+async def async_fn():
+
+    """Docstring."""
+
+    
+def top_level(
+    a: int,
+    b: str,
+) -> Whatever[Generic, Something]:
+
+    def nested(x: int) -> int:
+        pass
+
 # output
 
 def foo():
@@ -123,6 +142,25 @@ def quux():
 
 
 class Cls:
+
     def method(self):
 
         pass
+
+
+async def async_fn():
+    """Docstring."""
+
+
+@decorated
+async def async_fn():
+    """Docstring."""
+
+
+def top_level(
+    a: int,
+    b: str,
+) -> Whatever[Generic, Something]:
+
+    def nested(x: int) -> int:
+        pass

tests/data/cases/annotations.py

@@ -0,0 +1,17 @@
+# regression test for #1765
+class Foo:
+    def foo(self):
+        if True:
+            content_ids: Mapping[
+                str, Optional[ContentId]
+            ] = self.publisher_content_store.store_config_contents(files)
+
+# output
+
+# regression test for #1765
+class Foo:
+    def foo(self):
+        if True:
+            content_ids: Mapping[str, Optional[ContentId]] = (
+                self.publisher_content_store.store_config_contents(files)
+            )

tests/data/cases/async_stmts.py

@@ -1,4 +1,3 @@
-# flags: --preview
 async def func() -> (int):
     return 0
 

tests/data/cases/backslash_before_indent.py

@@ -0,0 +1,24 @@
+# flags: --minimum-version=3.10
+class Plotter:
+\
+    pass
+
+class AnotherCase:
+  \
+    """Some
+    \
+    Docstring
+    """
+
+# output
+
+class Plotter:
+
+    pass
+
+
+class AnotherCase:
+    """Some
+    \
+    Docstring
+    """

tests/data/cases/cantfit.py

@@ -1,4 +1,3 @@
-# flags: --preview
 # long variable name
 this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_like_it = 0
 this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_like_it = 1  # with a comment
@@ -20,12 +19,6 @@
 normal_name = but_the_function_name_is_now_ridiculously_long_and_it_is_still_super_annoying(
     [1, 2, 3], arg1, [1, 2, 3], arg2, [1, 2, 3], arg3
 )
-# long arguments
-normal_name = normal_function_name(
-    "but with super long string arguments that on their own exceed the line limit so there's no way it can ever fit",
-    "eggs with spam and eggs and spam with eggs with spam and eggs and spam with eggs with spam and eggs and spam with eggs",
-    this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_like_it=0,
-)
 string_variable_name = (
     "a string that is waaaaaaaayyyyyyyy too long, even in parens, there's nothing you can do"  # noqa
 )
@@ -38,7 +31,8 @@
         raise ValueError(err.format(key))
 concatenated_strings = "some strings that are " "concatenated implicitly, so if you put them on separate " "lines it will fit"
 del concatenated_strings, string_variable_name, normal_function_name, normal_name, need_more_to_make_the_line_long_enough
-
+del ([], name_1, name_2), [(), [], name_4, name_3], name_1[[name_2 for name_1 in name_0]]
+del (),
 
 # output
 
@@ -78,14 +72,6 @@
         [1, 2, 3], arg1, [1, 2, 3], arg2, [1, 2, 3], arg3
     )
 )
-# long arguments
-normal_name = normal_function_name(
-    "but with super long string arguments that on their own exceed the line limit so"
-    " there's no way it can ever fit",
-    "eggs with spam and eggs and spam with eggs with spam and eggs and spam with eggs"
-    " with spam and eggs and spam with eggs",
-    this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_like_it=0,
-)
 string_variable_name = "a string that is waaaaaaaayyyyyyyy too long, even in parens, there's nothing you can do"  # noqa
 for key in """
     hostname
@@ -106,3 +92,9 @@
     normal_name,
     need_more_to_make_the_line_long_enough,
 )
+del (
+    ([], name_1, name_2),
+    [(), [], name_4, name_3],
+    name_1[[name_2 for name_1 in name_0]],
+)
+del ((),)