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chore(deps): update dependency black to v24

Renovate Bot requested to merge renovate/black-24.x into main

This MR contains the following updates:

Package Type Update Change
black (changelog) dev major 22.10.0 -> 24.4.0

Release Notes

psf/black (black)


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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)
  • Add a new option use_pyproject to the GitHub Action psf/black. This will read the Black version from pyproject.toml. (#​4294)


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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)
  • Fix catastrophic performance on docstrings that contain large numbers of leading tab characters. This fixes CVE-2024-21503. (#​4278)
  • Note what happens when --check is used with --quiet (#​4236)


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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).
  • Fix issue where Black would ignore input files in the presence of symlinks (#​4222)
  • Black now ignores pyproject.toml that is missing a 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 [] to the previously discovered pyproject.toml (#​4204)
  • Black will swallow any SyntaxWarnings or DeprecationWarnings produced by the ast module when performing equivalence checks (#​4189)
  • Add a JSONSchema and provide a validate-pyproject entry-point (#​4181)


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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)
  • Shorten the length of the name of the cache file to fix crashes on file systems that do not support long paths (#​4176)


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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)
  • 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)
  • 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)


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


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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)
  • --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)


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  • 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)
  • Consistently apply force exclusion logic before resolving symlinks (#​4015)
  • Fix a bug in the matching of absolute path names in --include (#​3976)
  • Black's pre-commit integration will now run only on git hooks appropriate for a code formatter (#​3940)


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


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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)
  • Fix cache versioning logic when BLACK_CACHE_DIR is set (#​3937)
  • 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)
  • 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)
  • The action output displayed in the job summary is now wrapped in Markdown (#​3914)


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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.

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


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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)
  • Black now applies exclusion and ignore logic before resolving symlinks (#​3846)
  • Avoid importing IPython if notebook cells do not contain magics (#​3782)
  • Improve caching by comparing file hashes as fallback for mtime and size (#​3821)
  • Fix an issue in blackd with single character input (#​3558)
  • Black now has an official pre-commit mirror. Swapping to 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)


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  • Runtime support for Python 3.7 has been removed. Formatting 3.7 code will still be supported until further notice (#​3765)
Stable style
  • Fix a bug where an illegal trailing comma was added to return type annotations using PEP 604 unions (#​3735)
  • Fix several bugs and crashes where comments in stub files were removed or mishandled under some circumstances (#​3745)
  • Fix a crash with multi-line magic comments like type: ignore within parentheses (#​3740)
  • Fix error in AST validation when Black removes trailing whitespace in a type comment (#​3773)
Preview style
  • Implicitly concatenated strings used as function args are no longer wrapped inside parentheses (#​3640)
  • Remove blank lines between a class definition and its docstring (#​3692)
  • The --workers argument to Black can now be specified via the BLACK_NUM_WORKERS environment variable (#​3743)
  • .pytest_cache, .ruff_cache and .vscode are now excluded by default (#​3691)
  • Fix Black not honouring pyproject.toml settings when running --stdin-filename and the pyproject.toml found isn't in the current working directory (#​3719)
  • Black will now error if exclude and extend-exclude have invalid data types in pyproject.toml, instead of silently doing the wrong thing (#​3764)
  • Upgrade mypyc from 0.991 to 1.3 (#​3697)
  • Remove patching of Click that mitigated errors on Python 3.6 with LANG=C (#​3768)
  • Add support for the new PEP 695 syntax in Python 3.12 (#​3703)
  • Speed up Black significantly when the cache is full (#​3751)
  • Avoid importing IPython in a case where we wouldn't need it (#​3748)
  • Use aware UTC datetimes internally, avoids deprecation warning on Python 3.12 (#​3728)
  • Change verbose logging to exactly mirror Black's logic for source discovery (#​3749)
  • The blackd argument parser now shows the default values for options in their help text (#​3712)
  • Add a CITATION.cff file to the root of the repository, containing metadata on how to cite this software (#​3723)
  • Update the classes and exceptions documentation in Developer reference to match the latest code base (#​3755)


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This release fixes a longstanding confusing behavior in Black's GitHub action, where the version of the action did not determine the version of Black being run (issue #​3382). In addition, there is a small bug fix around imports and a number of improvements to the preview style.

Please try out the preview style with black --preview and tell us your feedback. All changes in the preview style are expected to become part of Black's stable style in January 2024.

Stable style
  • Import lines with # fmt: skip and # fmt: off no longer have an extra blank line added when they are right after another import line (#​3610)
Preview style
  • Add trailing commas to collection literals even if there's a comment after the last entry (#​3393)
  • async def, async for, and async with statements are now formatted consistently compared to their non-async version. (#​3609)
  • with statements that contain two context managers will be consistently wrapped in parentheses (#​3589)
  • Let string splitters respect East Asian Width (#​3445)
  • Now long string literals can be split after East Asian commas and periods (、 U+3001 IDEOGRAPHIC COMMA, 。 U+3002 IDEOGRAPHIC FULL STOP, & , U+FF0C FULLWIDTH COMMA) besides before spaces (#​3445)
  • For stubs, enforce one blank line after a nested class with a body other than just ... (#​3564)
  • Improve handling of multiline strings by changing line split behavior (#​1879)
  • Added support for formatting files with invalid type comments (#​3594)
  • Update GitHub Action to use the version of Black equivalent to action's version if version input is not specified (#​3543)
  • Fix missing Python binary path in autoload script for vim (#​3508)
  • Document that only the most recent release is supported for security issues; vulnerabilities should be reported through Tidelift (#​3612)


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This is the first release of 2023, and following our stability policy, it comes with a number of improvements to our stable style, including improvements to empty line handling, removal of redundant parentheses in several contexts, and output that highlights implicitly concatenated strings better.

There are also many changes to the preview style; try out black --preview and give us feedback to help us set the stable style for next year.

In addition to style changes, Black now automatically infers the supported Python versions from your pyproject.toml file, removing the need to set Black's target versions separately.

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
  • Format hex codes in unicode escape sequences in string literals (#​2916)
  • Add parentheses around if-else expressions (#​2278)
  • Improve performance on large expressions that contain many strings (#​3467)
  • Fix a crash in preview style with assert + parenthesized string (#​3415)
  • Fix crashes in preview style with walrus operators used in function return annotations and except clauses (#​3423)
  • Fix a crash in preview advanced string processing where mixed implicitly concatenated regular and f-strings start with an empty span (#​3463)
  • Fix a crash in preview advanced string processing where a standalone comment is placed before a dict's value (#​3469)
  • Fix an issue where extra empty lines are added when a decorator has # fmt: skip applied or there is a standalone comment between decorators (#​3470)
  • Do not put the closing quotes in a docstring on a separate line, even if the line is too long (#​3430)
  • 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)
  • Fix two crashes in preview style involving edge cases with docstrings (#​3451)
  • Exclude string type annotations from improved string processing; fix crash when the return type annotation is stringified and spans across multiple lines (#​3462)
  • Wrap multiple context managers in parentheses when targeting Python 3.9+ (#​3489)
  • Fix several crashes in preview style with walrus operators used in with statements or tuples (#​3473)
  • Fix an invalid quote escaping bug in f-string expressions where it produced invalid code. Implicitly concatenated f-strings with different quotes can now be merged or quote-normalized by changing the quotes used in expressions. (#​3509)
  • Fix crash on await (yield) when Black is compiled with mypyc (#​3533)
  • Black now tries to infer its --target-version from the project metadata specified in pyproject.toml (#​3219)
  • Upgrade mypyc from 0.971 to 0.991 so mypycified Black can be built on armv7 (#​3380)
    • This also fixes some crashes while using compiled Black with a debug build of CPython
  • Drop specific support for the tomli requirement on 3.11 alpha releases, working around a bug that would cause the requirement not to be installed on any non-final Python releases (#​3448)
  • Black now depends on packaging version 22.0 or later. This is required for new functionality that needs to parse part of the project metadata (#​3219)
  • Calling black --help multiple times will return the same help contents each time (#​3516)
  • Verbose logging now shows the values of pyproject.toml configuration variables (#​3392)
  • Fix false symlink detection messages in verbose output due to using an incorrect relative path to the project root (#​3385)
  • Move 3.11 CI to normal flow now that all dependencies support 3.11 (#​3446)
  • Docker: Add new latest_prerelease tag automation to follow latest black alpha release on docker images (#​3465)
  • Expand vim-plug installation instructions to offer more explicit options (#​3468)


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Preview style
  • Enforce empty lines before classes and functions with sticky leading comments (#​3302)
  • 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)
  • Implicitly concatenated strings used as function args are now wrapped inside parentheses (#​3307)
  • For assignment statements, prefer splitting the right hand side if the left hand side fits on a single line (#​3368)
  • Correctly handle trailing commas that are inside a line's leading non-nested parens (#​3370)
  • Fix incorrectly applied .gitignore rules by considering the .gitignore location and the relative path to the target file (#​3338)
  • Fix incorrectly ignoring .gitignore presence when more than one source directory is specified (#​3336)
  • Parsing support has been added for walruses inside generator expression that are passed as function args (for example, any(match := my_re.match(text) for text in texts)) (#​3327).
  • Vim plugin: Optionally allow using the system installation of Black via let g:black_use_virtualenv = 0(#​3309)


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