v24.3.0

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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.

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.
  (#​4278)

Documentation

• Note what happens when --check is used with --quiet (#​4236)

v24.2.0

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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 SyntaxWarnings or DeprecationWarnings produced by the ast
  module when performing equivalence checks (#​4189)

Integrations

• Add a JSONSchema and provide a validate-pyproject entry-point (#​4181)

v24.1.1

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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)

v24.1.0

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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. 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)