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Document each configuration option in more detail (#2839)

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8
docs/the_black_code_style/current_style.md
View File

@ -140,6 +140,8 @@ If you're reaching for backslashes, that's a clear signal that you can do better
slightly refactor your code. I hope some of the examples above show you that there are
many ways in which you can do it.
(labels/line-length)=
### Line length
You probably noticed the peculiar default line length. _Black_ defaults to 88 characters
@ -273,6 +275,8 @@ A pre-existing trailing comma informs _Black_ to always explode contents of the
bracket pair into one item per line. Read more about this in the
[Pragmatism](#pragmatism) section below.
(labels/strings)=
### Strings
_Black_ prefers double quotes (`"` and `"""`) over single quotes (`'` and `'''`). It
@ -457,6 +461,8 @@ there were not many users anyway. Not many edge cases were reported. As a mature
_Black_ does make some exceptions to rules it otherwise holds. This section documents
what those exceptions are and why this is the case.
(labels/magic-trailing-comma)=
### The magic trailing comma
_Black_ in general does not take existing formatting into account.
@ -493,6 +499,8 @@ default by (among others) GitHub and Visual Studio Code, differentiates between
r-strings and R-strings. The former are syntax highlighted as regular expressions while
the latter are treated as true raw strings with no special semantics.
(labels/ast-changes)=
### AST before and after formatting
When run with `--safe` (the default), _Black_ checks that the code before and after is

2
docs/the_black_code_style/future_style.md
View File

@ -47,6 +47,8 @@ with contextlib.ExitStack() as exit_stack:
...
```
(labels/preview-style)=
## Preview style
Experimental, potentially disruptive style changes are gathered under the `--preview`

292
docs/usage_and_configuration/the_basics.md
View File

@ -26,62 +26,106 @@ python -m black {source_file_or_directory}
### Command line options
The CLI options of _Black_ can be displayed by expanding the view below or by running
`black --help`. While _Black_ has quite a few knobs these days, it is still opinionated
so style options are deliberately limited and rarely added.
The CLI options of _Black_ can be displayed by running `black --help`. All options are
also covered in more detail below.
<details>
<summary>CLI reference</summary>
```{program-output} black --help
```
</details>
While _Black_ has quite a few knobs these days, it is still opinionated so style options
are deliberately limited and rarely added.
Note that all command-line options listed above can also be configured using a
`pyproject.toml` file (more on that below).
### Code input alternatives
#### `-c`, `--code`
#### Standard Input
_Black_ supports formatting code via stdin, with the result being printed to stdout.
Just let _Black_ know with `-` as the path.
```console
$ echo "print ( 'hello, world' )" | black -
print("hello, world")
reformatted -
All done! ✨ 🍰 ✨
1 file reformatted.
```
**Tip:** if you need _Black_ to treat stdin input as a file passed directly via the CLI,
use `--stdin-filename`. Useful to make sure _Black_ will respect the `--force-exclude`
option on some editors that rely on using stdin.
#### As a string
You can also pass code as a string using the `-c` / `--code` option.
Format the code passed in as a string.
```console
$ black --code "print ( 'hello, world' )"
print("hello, world")
```
### Writeback and reporting
#### `-l`, `--line-length`
By default _Black_ reformats the files given and/or found in place. Sometimes you need
_Black_ to just tell you what it _would_ do without actually rewriting the Python files.
How many characters per line to allow. The default is 88.
There's two variations to this mode that are independently enabled by their respective
flags. Both variations can be enabled at once.
See also [the style documentation](labels/line-length).
#### `-t`, `--target-version`
Python versions that should be supported by Black's output. You should include all
versions that your code supports. If you support Python 3.7 through 3.10, you should
write:
```console
$ black -t py37 -t py38 -t py39 -t py310
```
In a [configuration file](#configuration-via-a-file), you can write:
```toml
target-versions = ["py37", "py38", "py39", "py310"]
```
_Black_ uses this option to decide what grammar to use to parse your code. In addition,
it may use it to decide what style to use. For example, support for a trailing comma
after `*args` in a function call was added in Python 3.5, so _Black_ will add this comma
only if the target versions are all Python 3.5 or higher:
```console
$ black --line-length=10 --target-version=py35 -c 'f(a, *args)'
f(
a,
*args,
)
$ black --line-length=10 --target-version=py34 -c 'f(a, *args)'
f(
a,
*args
)
$ black --line-length=10 --target-version=py34 --target-version=py35 -c 'f(a, *args)'
f(
a,
*args
)
```
#### `--pyi`
Format all input files like typing stubs regardless of file extension. This is useful
when piping source on standard input.
#### `--ipynb`
Format all input files like Jupyter Notebooks regardless of file extension. This is
useful when piping source on standard input.
#### `--python-cell-magics`
When processing Jupyter Notebooks, add the given magic to the list of known python-
magics. Useful for formatting cells with custom python magics.
#### `-S, --skip-string-normalization`
By default, _Black_ uses double quotes for all strings and normalizes string prefixes,
as described in [the style documentation](labels/strings). If this option is given,
strings are left unchanged instead.
#### `-C, --skip-magic-trailing-comma`
By default, _Black_ uses existing trailing commas as an indication that short lines
should be left separate, as described in
[the style documentation](labels/magic-trailing-comma). If this option is given, the
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).
(labels/exit-code)=
#### Exit code
#### `--check`
Passing `--check` will make _Black_ exit with:
@ -111,12 +155,12 @@ $ echo $?
123
```
#### Diffs
#### `--diff`
Passing `--diff` will make _Black_ print out diffs that indicate what changes _Black_
would've made. They are printed to stdout so capturing them is simple.
If you'd like colored diffs, you can enable them with the `--color`.
If you'd like colored diffs, you can enable them with `--color`.
```console
$ black test.py --diff
@ -130,22 +174,92 @@ All done! ✨ 🍰 ✨
1 file would be reformatted.
```
### Output verbosity
#### `--color` / `--no-color`
_Black_ in general tries to produce the right amount of output, balancing between
usefulness and conciseness. By default, _Black_ emits files modified and error messages,
plus a short summary.
Show (or do not show) colored diff. Only applies when `--diff` is given.
#### `--fast` / `--safe`
By default, _Black_ performs [an AST safety check](labels/ast-changes) after formatting
your code. The `--fast` flag turns off this check and the `--safe` flag explicitly
enables it.
#### `--required-version`
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.
```console
$ black src/
error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
reformatted src/black_primer/lib.py
reformatted src/blackd/__init__.py
reformatted src/black/__init__.py
Oh no! 💥 💔 💥
3 files reformatted, 2 files left unchanged, 1 file failed to reformat.
$ black --version
black, 23.3.0 (compiled: yes)
$ black --required-version 23.3.0 -c "format = 'this'"
format = "this"
$ black --required-version 31.5b2 -c "still = 'beta?!'"
Oh no! 💥 💔 💥 The required version does not match the running version!
```
You can also pass just the major version:
```console
$ black --required-version 22 -c "format = 'this'"
format = "this"
$ black --required-version 31 -c "still = 'beta?!'"
Oh no! 💥 💔 💥 The required version does not match the running version!
```
Because of our [stability policy](../the_black_code_style/index.md), this will guarantee
stable formatting, but still allow you to take advantage of improvements that do not
affect formatting.
#### `--include`
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). Exclusions are
calculated first, inclusions later.
#### `--exclude`
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). Exclusions are calculated first, inclusions
later.
#### `--extend-exclude`
Like `--exclude`, but adds additional files and directories on top of the excluded ones.
Useful if you simply want to add to the default.
#### `--force-exclude`
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.
#### `--stdin-filename`
The name of the file when passing it through stdin. Useful to make sure Black will
respect the `--force-exclude` option on some editors that rely on using stdin.
#### `-W`, `--workers`
When _Black_ formats multiple files, it may use a process pool to speed up formatting.
This option controls the number of parallel workers.
#### `-q`, `--quiet`
Passing `-q` / `--quiet` will cause _Black_ to stop emitting all non-critical output.
Error messages will still be emitted (which can silenced by `2>/dev/null`).
```console
$ black src/ -q
error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
```
#### `-v`, `--verbose`
Passing `-v` / `--verbose` will cause _Black_ to also emit messages about files that
were not changed or were ignored due to exclusion patterns. If _Black_ is using a
configuration file, a blue message detailing which one it is using will be emitted.
@ -164,35 +278,73 @@ Oh no! 💥 💔 💥
3 files reformatted, 2 files left unchanged, 1 file failed to reformat
```
Passing `-q` / `--quiet` will cause _Black_ to stop emitting all non-critial output.
Error messages will still be emitted (which can silenced by `2>/dev/null`).
```console
$ black src/ -q
error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
```
### Versions
#### `--version`
You can check the version of _Black_ you have installed using the `--version` flag.
```console
$ black --version
black, version 23.3.0
black, 23.3.0
```
An option to require a specific version to be running is also provided.
#### `--config`
Read configuration options from a configuration file. See
[below](#configuration-via-a-file) for more details on the configuration file.
#### `-h`, `--help`
Show available command-line options and exit.
### Code input alternatives
_Black_ supports formatting code via stdin, with the result being printed to stdout.
Just let _Black_ know with `-` as the path.
```console
$ black --required-version 21.9b0 -c "format = 'this'"
format = "this"
$ black --required-version 31.5b2 -c "still = 'beta?!'"
Oh no! 💥 💔 💥 The required version does not match the running version!
$ echo "print ( 'hello, world' )" | black -
print("hello, world")
reformatted -
All done! ✨ 🍰 ✨
1 file reformatted.
```
This is useful for example when running _Black_ in multiple environments that haven't
necessarily installed the correct version. This option can be set in a configuration
file for consistent results across environments.
**Tip:** if you need _Black_ to treat stdin input as a file passed directly via the CLI,
use `--stdin-filename`. Useful to make sure _Black_ will respect the `--force-exclude`
option on some editors that rely on using stdin.
You can also pass code as a string using the `-c` / `--code` option.
### Writeback and reporting
By default _Black_ reformats the files given and/or found in place. Sometimes you need
_Black_ to just tell you what it _would_ do without actually rewriting the Python files.
There's two variations to this mode that are independently enabled by their respective
flags:
- `--check` (exit with code 1 if any file would be reformatted)
- `--diff` (print a diff instead of reformatting files)
Both variations can be enabled at once.
### Output verbosity
_Black_ in general tries to produce the right amount of output, balancing between
usefulness and conciseness. By default, _Black_ emits files modified and error messages,
plus a short summary.
```console
$ black src/
error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
reformatted src/black_primer/lib.py
reformatted src/blackd/__init__.py
reformatted src/black/__init__.py
Oh no! 💥 💔 💥
3 files reformatted, 2 files left unchanged, 1 file failed to reformat.
```
The `--quiet` and `--verbose` flags control output verbosity.
## Configuration via a file

17
scripts/check_version_in_basics_example.py
View File

@ -20,20 +20,21 @@ def main(changes: str, the_basics: str) -> None:
the_basics_html = commonmark.commonmark(the_basics)
the_basics_soup = BeautifulSoup(the_basics_html, "html.parser")
(version_example,) = [
version_examples = [
code_block.string
for code_block in the_basics_soup.find_all(class_="language-console")
if "$ black --version" in code_block.string
]
for tag in tags:
if tag in version_example and tag != latest_tag:
print(
"Please set the version in the ``black --version`` "
"example from ``the_basics.md`` to be the latest one.\n"
f"Expected {latest_tag}, got {tag}.\n"
)
sys.exit(1)
for version_example in version_examples:
if tag in version_example and tag != latest_tag:
print(
"Please set the version in the ``black --version`` "
"examples from ``the_basics.md`` to be the latest one.\n"
f"Expected {latest_tag}, got {tag}.\n"
)
sys.exit(1)
if __name__ == "__main__":