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)

v23.12.1

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Packaging

• Fixed a bug that included dependencies from the d extra by default (#​4108)

v23.12.0

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Highlights

It's almost 2024, which means it's time for a new edition of Black's stable style!
Together with this release, we'll put out an alpha release 24.1a1 showcasing the draft
2024 stable style, which we'll finalize in the January release. Please try it out and
share your feedback.

This release (23.12.0) will still produce the 2023 style. Most but not all of the
changes in --preview mode will be in the 2024 stable style.

Stable style

• Fix bug where # fmt: off automatically dedents when used with the --line-ranges
  option, even when it is not within the specified line range. (#​4084)
• Fix feature detection for parenthesized context managers (#​4104)

Preview style

• Prefer more equal signs before a break when splitting chained assignments (#​4010)
• Standalone form feed characters at the module level are no longer removed (#​4021)
• Additional cases of immediately nested tuples, lists, and dictionaries are now
  indented less (#​4012)
• Allow empty lines at the beginning of all blocks, except immediately before a
  docstring (#​4060)
• Fix crash in preview mode when using a short --line-length (#​4086)
• Keep suites consisting of only an ellipsis on their own lines if they are not
  functions or class definitions (#​4066) (#​4103)

Configuration

• --line-ranges now skips Black's internal stability check in --safe mode. This
  avoids a crash on rare inputs that have many unformatted same-content lines. (#​4034)

Packaging

• Upgrade to mypy 1.7.1 (#​4049) (#​4069)
• Faster compiled wheels are now available for CPython 3.12 (#​4070)

Integrations

• Enable 3.12 CI (#​4035)
• Build docker images in parallel (#​4054)
• Build docker images with 3.12 (#​4055)

v23.11.0

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Highlights

• Support formatting ranges of lines with the new --line-ranges command-line option
  (#​4020)

Stable style

• Fix crash on formatting bytes strings that look like docstrings (#​4003)
• Fix crash when whitespace followed a backslash before newline in a docstring (#​4008)
• Fix standalone comments inside complex blocks crashing Black (#​4016)
• Fix crash on formatting code like await (a ** b) (#​3994)
• No longer treat leading f-strings as docstrings. This matches Python's behaviour and
  fixes a crash (#​4019)

Preview style

• Multiline dicts and lists that are the sole argument to a function are now indented
  less (#​3964)
• Multiline unpacked dicts and lists as the sole argument to a function are now also
  indented less (#​3992)
• In f-string debug expressions, quote types that are visible in the final string are
  now preserved (#​4005)
• Fix a bug where long case blocks were not split into multiple lines. Also enable
  general trailing comma rules on case blocks (#​4024)
• Keep requiring two empty lines between module-level docstring and first function or
  class definition (#​4028)
• Add support for single-line format skip with other comments on the same line (#​3959)

Configuration

• Consistently apply force exclusion logic before resolving symlinks (#​4015)
• Fix a bug in the matching of absolute path names in --include (#​3976)

Performance

• Fix mypyc builds on arm64 on macOS (#​4017)

Integrations

• Black's pre-commit integration will now run only on git hooks appropriate for a code
  formatter (#​3940)

v23.10.1

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Highlights

• Maintenance release to get a fix out for GitHub Action edge case (#​3957)

Preview style

• Fix merging implicit multiline strings that have inline comments (#​3956)
• Allow empty first line after block open before a comment or compound statement (#​3967)

Packaging

• Change Dockerfile to hatch + compile black (#​3965)

Integrations

• The summary output for GitHub workflows is now suppressible using the summary
  parameter. (#​3958)
• Fix the action failing when Black check doesn't pass (#​3957)

Documentation

• It is known Windows documentation CI is broken
  https://github.com/psf/black/issues/39683968

v23.10.0

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Stable style

• Fix comments getting removed from inside parenthesized strings (#​3909)

Preview style

• Fix long lines with power operators getting split before the line length (#​3942)
• Long type hints are now wrapped in parentheses and properly indented when split across
  multiple lines (#​3899)
• Magic trailing commas are now respected in return types. (#​3916)
• Require one empty line after module-level docstrings. (#​3932)
• Treat raw triple-quoted strings as docstrings (#​3947)

Configuration

• Fix cache versioning logic when BLACK_CACHE_DIR is set (#​3937)

Parser

• Fix bug where attributes named type were not accepted inside match statements
  (#​3950)
• Add support for PEP 695 type aliases containing lambdas and other unusual expressions
  (#​3949)

Output

• Black no longer attempts to provide special errors for attempting to format Python 2
  code (#​3933)
• Black will more consistently print stacktraces on internal errors in verbose mode
  (#​3938)

Integrations

• The action output displayed in the job summary is now wrapped in Markdown (#​3914)

v23.9.1

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Due to various issues, the previous release (23.9.0) did not include compiled mypyc
wheels, which make Black significantly faster. These issues have now been fixed, and
this release should come with compiled wheels once again.

There will be no wheels for Python 3.12 due to a bug in mypyc. We will provide 3.12
wheels in a future release as soon as the mypyc bug is fixed.

Packaging

• Upgrade to mypy 1.5.1 (#​3864)

Performance

• Store raw tuples instead of NamedTuples in Black's cache, improving performance and
  decreasing the size of the cache (#​3877)

v23.9.0

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Preview style

• More concise formatting for dummy implementations (#​3796)
• In stub files, add a blank line between a statement with a body (e.g an
  if sys.version_info > (3, x):) and a function definition on the same level (#​3862)
• Fix a bug whereby spaces were removed from walrus operators within subscript(#​3823)

Configuration

• Black now applies exclusion and ignore logic before resolving symlinks (#​3846)

Performance

• Avoid importing IPython if notebook cells do not contain magics (#​3782)
• Improve caching by comparing file hashes as fallback for mtime and size (#​3821)

Blackd

• Fix an issue in blackd with single character input (#​3558)

Integrations

• Black now has an
  official pre-commit mirror. Swapping
  https://github.com/psf/black to https://github.com/psf/black-pre-commit-mirror in
  your .pre-commit-config.yaml will make Black about 2x faster (#​3828)
• The .black.env folder specified by ENV_PATH will now be removed on the completion
  of the GitHub Action (#​3759)