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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)

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)

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)

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 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)

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. 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)

Thank you

Thank you to everyone who provided feedback to help make Black's 2024 style even better. Thank you also to everyone who contributed code to Black.

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

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)

This is a preview of the 2024 stable style, showing the formatting that Black will use in 2024. Please test it out and share your feedback.

This applies the following changes:

• Multiline strings passed as the sole function arguments are formatted more compactly (#1879)
• 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)
• Standardize on a single newline after module docstrings (#3932)
• 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)

The following two changes may be included, but have outstanding issues that will need to be resolved:

• Long values in dict literals are now wrapped in parentheses; correspondingly unnecessary parentheses around short values in dict literals are now removed; long string lambda values are now wrapped in parentheses (#3440)
• Add parentheses around if-else expressions (#2278)