Draft for Black 2023 stable style (#3418)

CHANGES.md

@@ -10,6 +10,35 @@
 
 <!-- Changes that affect Black's stable style -->
 
+- Introduce the 2023 stable style, which incorporates most aspects of last year's
+  preview style (#3418). Specific changes:
+  - Enforce empty lines before classes and functions with sticky leading comments
+    (#3302) (22.12.0)
+  - Reformat empty and whitespace-only files as either an empty file (if no newline is
+    present) or as a single newline character (if a newline is present) (#3348)
+    (22.12.0)
+  - Implicitly concatenated strings used as function args are now wrapped inside
+    parentheses (#3307) (22.12.0)
+  - Correctly handle trailing commas that are inside a line's leading non-nested parens
+    (#3370) (22.12.0)
+  - `--skip-string-normalization` / `-S` now prevents docstring prefixes from being
+    normalized as expected (#3168) (since 22.8.0)
+  - When using `--skip-magic-trailing-comma` or `-C`, trailing commas are stripped from
+    subscript expressions with more than 1 element (#3209) (22.8.0)
+  - Implicitly concatenated strings inside a list, set, or tuple are now wrapped inside
+    parentheses (#3162) (22.8.0)
+  - Fix a string merging/split issue when a comment is present in the middle of
+    implicitly concatenated strings on its own line (#3227) (22.8.0)
+  - Docstring quotes are no longer moved if it would violate the line length limit
+    (#3044, #3430) (22.6.0)
+  - Parentheses around return annotations are now managed (#2990) (22.6.0)
+  - Remove unnecessary parentheses around awaited objects (#2991) (22.6.0)
+  - Remove unnecessary parentheses in `with` statements (#2926) (22.6.0)
+  - Remove trailing newlines after code block open (#3035) (22.6.0)
+  - Code cell separators `#%%` are now standardised to `# %%` (#2919) (22.3.0)
+  - Remove unnecessary parentheses from `except` statements (#2939) (22.3.0)
+  - Remove unnecessary parentheses from tuple unpacking in `for` loops (#2945) (22.3.0)
+  - Avoid magic-trailing-comma in single-element subscripts (#2942) (22.3.0)
 - Fix a crash when a colon line is marked between `# fmt: off` and `# fmt: on` (#3439)
 
 ### Preview style

docs/the_black_code_style/current_style.md

@@ -194,7 +194,45 @@ 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.
+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.
+
+```python
+# in:
+
+def foo():
+
+    print("All the newlines above me should be deleted!")
+
+
+if condition:
+
+    print("No newline above me!")
+
+    print("There is a newline above me, and that's OK!")
+
+
+class Point:
+
+    x: int
+    y: int
+
+# out:
+
+def foo():
+    print("All the newlines above me should be deleted!")
+
+
+if condition:
+    print("No newline above me!")
+
+    print("There is a newline above me, and that's OK!")
+
+
+class Point:
+    x: int
+    y: int
+```
 
 It will also insert proper spacing before and after function definitions. It's one line
 before and after inner functions and two lines before and after module-level functions

docs/the_black_code_style/future_style.md

@@ -62,93 +62,3 @@ plain strings. User-made splits are respected when they do not exceed the line l
 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).
-
-### Improved empty line management
-
-1.  _Black_ will remove newlines in the beginning of new code blocks, i.e. when the
-    indentation level is increased. For example:
-
-    ```python
-    def my_func():
-
-        print("The line above me will be deleted!")
-    ```
-
-    will be changed to:
-
-    ```python
-    def my_func():
-        print("The line above me will be deleted!")
-    ```
-
-    This new feature will be applied to **all code blocks**: `def`, `class`, `if`,
-    `for`, `while`, `with`, `case` and `match`.
-
-2.  _Black_ will enforce empty lines before classes and functions with leading comments.
-    For example:
-
-    ```python
-    some_var = 1
-    # Leading sticky comment
-    def my_func():
-        ...
-    ```
-
-    will be changed to:
-
-    ```python
-    some_var = 1
-
-
-    # Leading sticky comment
-    def my_func():
-        ...
-    ```
-
-### Improved parentheses management
-
-_Black_ will format parentheses around return annotations similarly to other sets of
-parentheses. For example:
-
-```python
-def foo() -> (int):
-    ...
-
-def foo() -> looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong:
-    ...
-```
-
-will be changed to:
-
-```python
-def foo() -> int:
-    ...
-
-
-def foo() -> (
-    looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
-):
-    ...
-```
-
-And, extra parentheses in `await` expressions and `with` statements are removed. For
-example:
-
-```python
-with ((open("bla.txt")) as f, open("x")):
-    ...
-
-async def main():
-    await (asyncio.sleep(1))
-```
-
-will be changed to:
-
-```python
-with open("bla.txt") as f, open("x"):
-    ...
-
-
-async def main():
-    await asyncio.sleep(1)
-```

src/black/__init__.py

@@ -925,9 +925,6 @@ def format_file_contents(src_contents: str, *, fast: bool, mode: Mode) -> FileCo
     valid by calling :func:`assert_equivalent` and :func:`assert_stable` on it.
     `mode` is passed to :func:`format_str`.
     """
-    if not mode.preview and not src_contents.strip():
-        raise NothingChanged
-
     if mode.is_ipynb:
         dst_contents = format_ipynb_string(src_contents, fast=fast, mode=mode)
     else:
@@ -1022,7 +1019,7 @@ def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileCon
     Operate cell-by-cell, only on code cells, only for Python notebooks.
     If the ``.ipynb`` originally had a trailing newline, it'll be preserved.
     """
-    if mode.preview and not src_contents:
+    if not src_contents:
         raise NothingChanged
 
     trailing_newline = src_contents[-1] == "\n"
@@ -1101,7 +1098,7 @@ def _format_str_once(src_contents: str, *, mode: Mode) -> str:
         for feature in {Feature.PARENTHESIZED_CONTEXT_MANAGERS}
         if supports_feature(versions, feature)
     }
-    normalize_fmt_off(src_node, preview=mode.preview)
+    normalize_fmt_off(src_node)
     lines = LineGenerator(mode=mode, features=context_manager_features)
     elt = EmptyLineTracker(mode=mode)
     split_line_features = {
@@ -1122,7 +1119,7 @@ def _format_str_once(src_contents: str, *, mode: Mode) -> str:
     dst_contents = []
     for block in dst_blocks:
         dst_contents.extend(block.all_lines())
-    if mode.preview and not dst_contents:
+    if not dst_contents:
         # Use decode_bytes to retrieve the correct source newline (CRLF or LF),
         # and check if normalized_content has more than one line
         normalized_content, _, newline = decode_bytes(src_contents.encode("utf-8"))

src/black/comments.py

@@ -29,7 +29,7 @@
 FMT_PASS: Final = {*FMT_OFF, *FMT_SKIP}
 FMT_ON: Final = {"# fmt: on", "# fmt:on", "# yapf: enable"}
 
-COMMENT_EXCEPTIONS = {True: " !:#'", False: " !:#'%"}
+COMMENT_EXCEPTIONS = " !:#'"
 
 
 @dataclass
@@ -50,7 +50,7 @@ class ProtoComment:
     consumed: int  # how many characters of the original leaf's prefix did we consume
 
 
-def generate_comments(leaf: LN, *, preview: bool) -> Iterator[Leaf]:
+def generate_comments(leaf: LN) -> Iterator[Leaf]:
     """Clean the prefix of the `leaf` and generate comments from it, if any.
 
     Comments in lib2to3 are shoved into the whitespace prefix.  This happens
@@ -69,16 +69,12 @@ def generate_comments(leaf: LN, *, preview: bool) -> Iterator[Leaf]:
     Inline comments are emitted as regular token.COMMENT leaves.  Standalone
     are emitted with a fake STANDALONE_COMMENT token identifier.
     """
-    for pc in list_comments(
+    for pc in list_comments(leaf.prefix, is_endmarker=leaf.type == token.ENDMARKER):
-        leaf.prefix, is_endmarker=leaf.type == token.ENDMARKER, preview=preview
-    ):
         yield Leaf(pc.type, pc.value, prefix="\n" * pc.newlines)
 
 
 @lru_cache(maxsize=4096)
-def list_comments(
+def list_comments(prefix: str, *, is_endmarker: bool) -> List[ProtoComment]:
-    prefix: str, *, is_endmarker: bool, preview: bool
-) -> List[ProtoComment]:
     """Return a list of :class:`ProtoComment` objects parsed from the given `prefix`."""
     result: List[ProtoComment] = []
     if not prefix or "#" not in prefix:
@@ -104,7 +100,7 @@ def list_comments(
             comment_type = token.COMMENT  # simple trailing comment
         else:
             comment_type = STANDALONE_COMMENT
-        comment = make_comment(line, preview=preview)
+        comment = make_comment(line)
         result.append(
             ProtoComment(
                 type=comment_type, value=comment, newlines=nlines, consumed=consumed
@@ -114,7 +110,7 @@ def list_comments(
     return result
 
 
-def make_comment(content: str, *, preview: bool) -> str:
+def make_comment(content: str) -> str:
     """Return a consistently formatted comment from the given `content` string.
 
     All comments (except for "##", "#!", "#:", '#'") should have a single
@@ -135,26 +131,26 @@ def make_comment(content: str, *, preview: bool) -> str:
         and not content.lstrip().startswith("type:")
     ):
         content = " " + content[1:]  # Replace NBSP by a simple space
-    if content and content[0] not in COMMENT_EXCEPTIONS[preview]:
+    if content and content[0] not in COMMENT_EXCEPTIONS:
         content = " " + content
     return "#" + content
 
 
-def normalize_fmt_off(node: Node, *, preview: bool) -> None:
+def normalize_fmt_off(node: Node) -> None:
     """Convert content between `# fmt: off`/`# fmt: on` into standalone comments."""
     try_again = True
     while try_again:
-        try_again = convert_one_fmt_off_pair(node, preview=preview)
+        try_again = convert_one_fmt_off_pair(node)
 
 
-def convert_one_fmt_off_pair(node: Node, *, preview: bool) -> bool:
+def convert_one_fmt_off_pair(node: Node) -> bool:
     """Convert content of a single `# fmt: off`/`# fmt: on` into a standalone comment.
 
     Returns True if a pair was converted.
     """
     for leaf in node.leaves():
         previous_consumed = 0
-        for comment in list_comments(leaf.prefix, is_endmarker=False, preview=preview):
+        for comment in list_comments(leaf.prefix, is_endmarker=False):
             if comment.value not in FMT_PASS:
                 previous_consumed = comment.consumed
                 continue
@@ -169,7 +165,7 @@ def convert_one_fmt_off_pair(node: Node, *, preview: bool) -> bool:
                     if comment.value in FMT_SKIP and prev.type in WHITESPACE:
                         continue
 
-            ignored_nodes = list(generate_ignored_nodes(leaf, comment, preview=preview))
+            ignored_nodes = list(generate_ignored_nodes(leaf, comment))
             if not ignored_nodes:
                 continue
 
@@ -214,26 +210,24 @@ def convert_one_fmt_off_pair(node: Node, *, preview: bool) -> bool:
     return False
 
 
-def generate_ignored_nodes(
+def generate_ignored_nodes(leaf: Leaf, comment: ProtoComment) -> Iterator[LN]:
-    leaf: Leaf, comment: ProtoComment, *, preview: bool
-) -> Iterator[LN]:
     """Starting from the container of `leaf`, generate all leaves until `# fmt: on`.
 
     If comment is skip, returns leaf only.
     Stops at the end of the block.
     """
     if comment.value in FMT_SKIP:
-        yield from _generate_ignored_nodes_from_fmt_skip(leaf, comment, preview=preview)
+        yield from _generate_ignored_nodes_from_fmt_skip(leaf, comment)
         return
     container: Optional[LN] = container_of(leaf)
     while container is not None and container.type != token.ENDMARKER:
-        if is_fmt_on(container, preview=preview):
+        if is_fmt_on(container):
             return
 
         # fix for fmt: on in children
-        if children_contains_fmt_on(container, preview=preview):
+        if children_contains_fmt_on(container):
             for index, child in enumerate(container.children):
-                if isinstance(child, Leaf) and is_fmt_on(child, preview=preview):
+                if isinstance(child, Leaf) and is_fmt_on(child):
                     if child.type in CLOSING_BRACKETS:
                         # This means `# fmt: on` is placed at a different bracket level
                         # than `# fmt: off`. This is an invalid use, but as a courtesy,
@@ -244,14 +238,12 @@ def generate_ignored_nodes(
                 if (
                     child.type == token.INDENT
                     and index < len(container.children) - 1
-                    and children_contains_fmt_on(
+                    and children_contains_fmt_on(container.children[index + 1])
-                        container.children[index + 1], preview=preview
-                    )
                 ):
                     # This means `# fmt: on` is placed right after an indentation
                     # level, and we shouldn't swallow the previous INDENT token.
                     return
-                if children_contains_fmt_on(child, preview=preview):
+                if children_contains_fmt_on(child):
                     return
                 yield child
         else:
@@ -264,14 +256,14 @@ def generate_ignored_nodes(
 
 
 def _generate_ignored_nodes_from_fmt_skip(
-    leaf: Leaf, comment: ProtoComment, *, preview: bool
+    leaf: Leaf, comment: ProtoComment
 ) -> Iterator[LN]:
     """Generate all leaves that should be ignored by the `# fmt: skip` from `leaf`."""
     prev_sibling = leaf.prev_sibling
     parent = leaf.parent
     # 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, preview=preview)
+    comments = list_comments(leaf.prefix, is_endmarker=False)
     if not comments or comment.value != comments[0].value:
         return
     if prev_sibling is not None:
@@ -305,12 +297,12 @@ def _generate_ignored_nodes_from_fmt_skip(
         yield from iter(ignored_nodes)
 
 
-def is_fmt_on(container: LN, preview: bool) -> bool:
+def is_fmt_on(container: LN) -> bool:
     """Determine whether formatting is switched on within a container.
     Determined by whether the last `# fmt:` comment is `on` or `off`.
     """
     fmt_on = False
-    for comment in list_comments(container.prefix, is_endmarker=False, preview=preview):
+    for comment in list_comments(container.prefix, is_endmarker=False):
         if comment.value in FMT_ON:
             fmt_on = True
         elif comment.value in FMT_OFF:
@@ -318,11 +310,11 @@ def is_fmt_on(container: LN, preview: bool) -> bool:
     return fmt_on
 
 
-def children_contains_fmt_on(container: LN, *, preview: bool) -> bool:
+def children_contains_fmt_on(container: LN) -> bool:
     """Determine if children have formatting switched on."""
     for child in container.children:
         leaf = first_leaf_of(child)
-        if leaf is not None and is_fmt_on(leaf, preview=preview):
+        if leaf is not None and is_fmt_on(leaf):
             return True
 
     return False

src/black/linegen.py

@@ -117,7 +117,7 @@ def visit_default(self, node: LN) -> Iterator[Line]:
         """Default `visit_*()` implementation. Recurses to children of `node`."""
         if isinstance(node, Leaf):
             any_open_brackets = self.current_line.bracket_tracker.any_open_brackets()
-            for comment in generate_comments(node, preview=self.mode.preview):
+            for comment in generate_comments(node):
                 if any_open_brackets:
                     # any comment within brackets is subject to splitting
                     self.current_line.append(comment)
@@ -221,30 +221,27 @@ def visit_dictsetmaker(self, node: Node) -> Iterator[Line]:
 
     def visit_funcdef(self, node: Node) -> Iterator[Line]:
         """Visit function definition."""
-        if Preview.annotation_parens not in self.mode:
+        yield from self.line()
-            yield from self.visit_stmt(node, keywords={"def"}, parens=set())
-        else:
-            yield from self.line()
 
-            # Remove redundant brackets around return type annotation.
+        # Remove redundant brackets around return type annotation.
-            is_return_annotation = False
+        is_return_annotation = False
-            for child in node.children:
+        for child in node.children:
-                if child.type == token.RARROW:
+            if child.type == token.RARROW:
-                    is_return_annotation = True
+                is_return_annotation = True
-                elif is_return_annotation:
+            elif is_return_annotation:
-                    if child.type == syms.atom and child.children[0].type == token.LPAR:
+                if child.type == syms.atom and child.children[0].type == token.LPAR:
-                        if maybe_make_parens_invisible_in_atom(
+                    if maybe_make_parens_invisible_in_atom(
-                            child,
+                        child,
-                            parent=node,
+                        parent=node,
-                            remove_brackets_around_comma=False,
+                        remove_brackets_around_comma=False,
-                        ):
+                    ):
-                            wrap_in_parentheses(node, child, visible=False)
-                    else:
                         wrap_in_parentheses(node, child, visible=False)
-                    is_return_annotation = False
+                else:
+                    wrap_in_parentheses(node, child, visible=False)
+                is_return_annotation = False
 
-            for child in node.children:
+        for child in node.children:
-                yield from self.visit(child)
+            yield from self.visit(child)
 
     def visit_match_case(self, node: Node) -> Iterator[Line]:
         """Visit either a match or case statement."""
@@ -332,8 +329,7 @@ def visit_power(self, node: Node) -> Iterator[Line]:
             ):
                 wrap_in_parentheses(node, leaf)
 
-        if Preview.remove_redundant_parens in self.mode:
+        remove_await_parens(node)
-            remove_await_parens(node)
 
         yield from self.visit_default(node)
 
@@ -375,24 +371,17 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
         if is_docstring(leaf) and "\\\n" not in leaf.value:
             # We're ignoring docstrings with backslash newline escapes because changing
             # indentation of those changes the AST representation of the code.
-            if Preview.normalize_docstring_quotes_and_prefixes_properly in self.mode:
+            if self.mode.string_normalization:
-                # There was a bug where --skip-string-normalization wouldn't stop us
-                # from normalizing docstring prefixes. To maintain stability, we can
-                # only address this buggy behaviour while the preview style is enabled.
-                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.
-                    # 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.
-                    docstring = normalize_string_quotes(docstring)
-                else:
-                    docstring = leaf.value
-            else:
-                # ... otherwise, we'll keep the buggy behaviour >.<
                 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.
+                # 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.
+                docstring = normalize_string_quotes(docstring)
+            else:
+                docstring = leaf.value
             prefix = get_string_prefix(docstring)
             docstring = docstring[len(prefix) :]  # Remove the prefix
             quote_char = docstring[0]
@@ -432,7 +421,7 @@ 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 Preview.long_docstring_quotes_on_newline in self.mode and quote_len == 3:
+            if self.mode and 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.
@@ -473,14 +462,8 @@ def __post_init__(self) -> None:
         self.visit_try_stmt = partial(
             v, keywords={"try", "except", "else", "finally"}, parens=Ø
         )
-        if self.mode.preview:
+        self.visit_except_clause = partial(v, keywords={"except"}, parens={"except"})
-            self.visit_except_clause = partial(
+        self.visit_with_stmt = partial(v, keywords={"with"}, parens={"with"})
-                v, keywords={"except"}, parens={"except"}
-            )
-            self.visit_with_stmt = partial(v, keywords={"with"}, parens={"with"})
-        else:
-            self.visit_except_clause = partial(v, keywords={"except"}, parens=Ø)
-            self.visit_with_stmt = partial(v, keywords={"with"}, parens=Ø)
         self.visit_classdef = partial(v, keywords={"class"}, parens=Ø)
         self.visit_expr_stmt = partial(v, keywords=Ø, parens=ASSIGNMENTS)
         self.visit_return_stmt = partial(v, keywords={"return"}, parens={"return"})
@@ -932,10 +915,7 @@ def bracket_split_build_line(
                     break
 
     leaves_to_track: Set[LeafID] = set()
-    if (
+    if component is _BracketSplitComponent.head:
-        Preview.handle_trailing_commas_in_head in original.mode
-        and component is _BracketSplitComponent.head
-    ):
         leaves_to_track = get_leaves_inside_matching_brackets(leaves)
     # Populate the line
     for leaf in leaves:
@@ -1109,7 +1089,7 @@ def normalize_invisible_parens(
     Standardizes on visible parentheses for single-element tuples, and keeps
     existing visible parentheses for other tuples and generator expressions.
     """
-    for pc in list_comments(node.prefix, is_endmarker=False, preview=mode.preview):
+    for pc in list_comments(node.prefix, is_endmarker=False):
         if pc.value in FMT_OFF:
             # This `node` has a prefix with `# fmt: off`, don't mess with parens.
             return
@@ -1139,8 +1119,7 @@ def normalize_invisible_parens(
 
         if check_lpar:
             if (
-                mode.preview
+                child.type == syms.atom
-                and child.type == syms.atom
                 and node.type == syms.for_stmt
                 and isinstance(child.prev_sibling, Leaf)
                 and child.prev_sibling.type == token.NAME
@@ -1152,9 +1131,7 @@ def normalize_invisible_parens(
                     remove_brackets_around_comma=True,
                 ):
                     wrap_in_parentheses(node, child, visible=False)
-            elif (
+            elif isinstance(child, Node) and node.type == syms.with_stmt:
-                mode.preview and isinstance(child, Node) and node.type == syms.with_stmt
-            ):
                 remove_with_parens(child, node)
             elif child.type == syms.atom:
                 if maybe_make_parens_invisible_in_atom(
@@ -1180,7 +1157,7 @@ def normalize_invisible_parens(
             elif not (isinstance(child, Leaf) and is_multiline_string(child)):
                 wrap_in_parentheses(node, child, visible=False)
 
-        comma_check = child.type == token.COMMA if mode.preview else False
+        comma_check = child.type == token.COMMA
 
         check_lpar = isinstance(child, Leaf) and (
             child.value in parens_after or comma_check

src/black/lines.py

@@ -14,7 +14,7 @@
 )
 
 from black.brackets import DOT_PRIORITY, BracketTracker
-from black.mode import Mode, Preview
+from black.mode import Mode
 from black.nodes import (
     BRACKETS,
     CLOSING_BRACKETS,
@@ -275,8 +275,7 @@ def has_magic_trailing_comma(
         - it's not a single-element subscript
         Additionally, if ensure_removable:
         - it's not from square bracket indexing
-        (specifically, single-element square bracket indexing with
+        (specifically, single-element square bracket indexing)
-        Preview.skip_magic_trailing_comma_in_subscript)
         """
         if not (
             closing.type in CLOSING_BRACKETS
@@ -290,8 +289,7 @@ def has_magic_trailing_comma(
 
         if closing.type == token.RSQB:
             if (
-                Preview.one_element_subscript in self.mode
+                closing.parent
-                and closing.parent
                 and closing.parent.type == syms.trailer
                 and closing.opening_bracket
                 and is_one_sequence_between(
@@ -309,18 +307,16 @@ def has_magic_trailing_comma(
             comma = self.leaves[-1]
             if comma.parent is None:
                 return False
-            if Preview.skip_magic_trailing_comma_in_subscript in self.mode:
+            return (
-                return (
+                comma.parent.type != syms.subscriptlist
-                    comma.parent.type != syms.subscriptlist
+                or closing.opening_bracket is None
-                    or closing.opening_bracket is None
+                or not is_one_sequence_between(
-                    or not is_one_sequence_between(
+                    closing.opening_bracket,
-                        closing.opening_bracket,
+                    closing,
-                        closing,
+                    self.leaves,
-                        self.leaves,
+                    brackets=(token.LSQB, token.RSQB),
-                        brackets=(token.LSQB, token.RSQB),
-                    )
                 )
-            return comma.parent.type == syms.listmaker
+            )
 
         if self.is_import:
             return True
@@ -592,11 +588,7 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
         ):
             return before, 1
 
-        if (
+        if self.previous_line and self.previous_line.opens_block:
-            Preview.remove_block_trailing_newline in current_line.mode
-            and self.previous_line
-            and self.previous_line.opens_block
-        ):
             return 0, 0
         return before, 0
 
@@ -629,9 +621,7 @@ def _maybe_empty_lines_for_class_or_def(
         ):
             slc = self.semantic_leading_comment
             if (
-                Preview.empty_lines_before_class_or_def_with_leading_comments
+                slc is not None
-                in current_line.mode
-                and slc is not None
                 and slc.previous_block is not None
                 and not slc.previous_block.original_line.is_class
                 and not slc.previous_block.original_line.opens_block

src/black/mode.py

@@ -154,15 +154,7 @@ class Preview(Enum):
     """Individual preview style features."""
 
     hex_codes_in_unicode_sequences = auto()
-    annotation_parens = auto()
-    empty_lines_before_class_or_def_with_leading_comments = auto()
-    handle_trailing_commas_in_head = auto()
-    long_docstring_quotes_on_newline = auto()
-    normalize_docstring_quotes_and_prefixes_properly = auto()
-    one_element_subscript = auto()
     prefer_splitting_right_hand_side_of_assignments = auto()
-    remove_block_trailing_newline = auto()
-    remove_redundant_parens = 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()

tests/data/miscellaneous/expression_skip_magic_trailing_comma.diff

@@ -144,8 +144,9 @@
 -tuple[
 -    str, int, float, dict[str, int]
 -]
+-tuple[str, int, float, dict[str, int],]
++tuple[str, int, float, dict[str, int]]
 +tuple[str, int, float, dict[str, int]]
- tuple[str, int, float, dict[str, int],]
  very_long_variable_name_filters: t.List[
      t.Tuple[str, t.Union[str, t.List[t.Optional[str]]]],
  ]

tests/data/preview/return_annotation_brackets_string.py

@@ -0,0 +1,12 @@
+# Long string example
+def frobnicate() -> "ThisIsTrulyUnreasonablyExtremelyLongClassName | list[ThisIsTrulyUnreasonablyExtremelyLongClassName]":
+    pass
+
+# output
+
+# Long string example
+def frobnicate() -> (
+    "ThisIsTrulyUnreasonablyExtremelyLongClassName |"
+    " list[ThisIsTrulyUnreasonablyExtremelyLongClassName]"
+):
+    pass

tests/data/py_310/parenthesized_context_managers.py

@@ -19,3 +19,27 @@
     CtxManager3() as example3,
 ):
     ...
+
+# output
+
+with CtxManager() as example:
+    ...
+
+with CtxManager1(), CtxManager2():
+    ...
+
+with CtxManager1() as example, CtxManager2():
+    ...
+
+with CtxManager1(), CtxManager2() as example:
+    ...
+
+with CtxManager1() as example1, CtxManager2() as example2:
+    ...
+
+with (
+    CtxManager1() as example1,
+    CtxManager2() as example2,
+    CtxManager3() as example3,
+):
+    ...

tests/data/py_311/pep_654_style.py

@@ -76,7 +76,7 @@
     except:
         try:
             raise TypeError(int)
-        except* (Exception):
+        except* Exception:
             pass
         1 / 0
 except Exception as e:

tests/data/py_38/pep_572_remove_parens.py

@@ -62,7 +62,6 @@ async def await_the_walrus():
     with (x := await a, y := await b):
         pass
 
-    # Ideally we should remove one set of parentheses
     with ((x := await a, y := await b)):
         pass
 
@@ -137,8 +136,7 @@ async def await_the_walrus():
     with (x := await a, y := await b):
         pass
 
-    # Ideally we should remove one set of parentheses
+    with (x := await a, y := await b):
-    with ((x := await a, y := await b)):
         pass
 
     with (x := await a), (y := await b):

tests/data/simple_cases/comments2.py

@@ -226,6 +226,7 @@ def _init_host(self, parsed) -> None:
     add_compiler(compilers[(7.0, 32)])
     # add_compiler(compilers[(7.1, 64)])
 
+
 # Comment before function.
 def inline_comments_in_brackets_ruin_everything():
     if typedargslist:

tests/data/simple_cases/comments3.py

@@ -1,6 +1,7 @@
 # The percent-percent comments are Spyder IDE cells.
 
-#%%
+
+# %%
 def func():
     x = """
     a really long string
@@ -44,4 +45,4 @@ def func():
     )
 
 
-#%%
+# %%

tests/data/simple_cases/comments5.py

@@ -62,6 +62,8 @@ def decorated1():
 # Preview.empty_lines_before_class_or_def_with_leading_comments.
 # In the current style, the user will have to split those lines by hand.
 some_instruction
+
+
 # This comment should be split from `some_instruction` by two lines but isn't.
 def g():
     ...

tests/data/simple_cases/empty_lines.py

@@ -119,7 +119,6 @@ def f():
     if not prev:
         prevp = preceding_leaf(p)
         if not prevp or prevp.type in OPENING_BRACKETS:
-
             return NO
 
         if prevp.type == token.EQUAL:

tests/data/simple_cases/fmtonoff.py

@@ -205,6 +205,7 @@ def single_literal_yapf_disable():
 
 # Comment 2
 
+
 # fmt: off
 def func_no_args():
   a; b; c

tests/data/simple_cases/function_trailing_comma.py

@@ -116,9 +116,9 @@ def f(
         pass
 
 
-def xxxxxxxxxxxxxxxxxxxxxxxxxxxx() -> Set[
+def xxxxxxxxxxxxxxxxxxxxxxxxxxxx() -> (
-    "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+    Set["xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"]
-]:
+):
     json = {
         "k": {
             "k2": {
@@ -140,9 +140,7 @@ def some_function_with_a_really_long_name() -> (
 
 def some_method_with_a_really_long_name(
     very_long_parameter_so_yeah: str, another_long_parameter: int
-) -> (
+) -> another_case_of_returning_a_deeply_nested_import_of_a_type_i_suppose_cause_why_not:
-    another_case_of_returning_a_deeply_nested_import_of_a_type_i_suppose_cause_why_not
-):
     pass
 
 
@@ -155,10 +153,8 @@ def func() -> (
 
 
 def func() -> (
-    (
+    also_super_long_type_annotation_that_may_cause_an_AST_related_crash_in_black(
-        also_super_long_type_annotation_that_may_cause_an_AST_related_crash_in_black(
+        this_shouldn_t_get_a_trailing_comma_too
-            this_shouldn_t_get_a_trailing_comma_too
-        )
     )
 ):
     pass

tests/data/simple_cases/return_annotation_brackets.py

@@ -87,10 +87,6 @@ def foo() -> tuple[loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
 def foo() -> tuple[int, int, int,]:
     return 2
 
-# Long string example
-def frobnicate() -> "ThisIsTrulyUnreasonablyExtremelyLongClassName | list[ThisIsTrulyUnreasonablyExtremelyLongClassName]":
-    pass
-
 # output
 # Control
 def double(a: int) -> int:
@@ -212,11 +208,3 @@ def foo() -> (
     ]
 ):
     return 2
-
-
-# Long string example
-def frobnicate() -> (
-    "ThisIsTrulyUnreasonablyExtremelyLongClassName |"
-    " list[ThisIsTrulyUnreasonablyExtremelyLongClassName]"
-):
-    pass

tests/test_black.py

@@ -419,7 +419,8 @@ def test_skip_magic_trailing_comma(self) -> None:
             msg = (
                 "Expected diff isn't equal to the actual. If you made changes to"
                 " expression.py and this is an anticipated difference, overwrite"
-                f" tests/data/expression_skip_magic_trailing_comma.diff with {dump}"
+                " tests/data/miscellaneous/expression_skip_magic_trailing_comma.diff"
+                f" with {dump}"
             )
             self.assertEqual(expected, actual, msg)
 

tests/test_format.py

@@ -32,31 +32,15 @@ def check_file(
 @pytest.mark.filterwarnings("ignore:invalid escape sequence.*:DeprecationWarning")
 @pytest.mark.parametrize("filename", all_data_cases("simple_cases"))
 def test_simple_format(filename: str) -> None:
-    check_file("simple_cases", filename, DEFAULT_MODE)
+    magic_trailing_comma = filename != "skip_magic_trailing_comma"
+    check_file(
+        "simple_cases", filename, black.Mode(magic_trailing_comma=magic_trailing_comma)
+    )
 
 
 @pytest.mark.parametrize("filename", all_data_cases("preview"))
 def test_preview_format(filename: str) -> None:
-    magic_trailing_comma = filename != "skip_magic_trailing_comma"
+    check_file("preview", filename, black.Mode(preview=True))
-    check_file(
-        "preview",
-        filename,
-        black.Mode(preview=True, magic_trailing_comma=magic_trailing_comma),
-    )
-
-
-@pytest.mark.parametrize("filename", all_data_cases("preview_39"))
-def test_preview_minimum_python_39_format(filename: str) -> None:
-    source, expected = read_data("preview_39", filename)
-    mode = black.Mode(preview=True)
-    assert_format(source, expected, mode, minimum_version=(3, 9))
-
-
-@pytest.mark.parametrize("filename", all_data_cases("preview_310"))
-def test_preview_minimum_python_310_format(filename: str) -> None:
-    source, expected = read_data("preview_310", filename)
-    mode = black.Mode(preview=True)
-    assert_format(source, expected, mode, minimum_version=(3, 10))
 
 
 def test_preview_context_managers_targeting_py38() -> None: