Black

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/3968

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)

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)

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](https://github.com/psf/black-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)

Highlights

- 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)

Configuration

- 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)

Packaging

- Upgrade mypyc from 0.991 to 1.3 (3697)
- Remove patching of Click that mitigated errors on Python 3.6 with `LANG=C` (3768)

Parser

- Add support for the new PEP 695 syntax in Python 3.12 (3703)

Performance

- Speed up _Black_ significantly when the cache is full (3751)
- Avoid importing `IPython` in a case where we wouldn't need it (3748)

Output

- 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)

_Blackd_

- The `blackd` argument parser now shows the default values for options in their help
text (3712)

Integrations

- Black is now tested with
[`PYTHONWARNDEFAULTENCODING = 1`](https://docs.python.org/3/library/io.html#io-encoding-warning)
(3763)
- Update GitHub Action to display black output in the job summary (3688)

Documentation

- 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)

Highlights

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](https://black.readthedocs.io/en/stable/the_black_code_style/future_style.html#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](https://www.unicode.org/reports/tr11/)
(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)

Parser

- Added support for formatting files with invalid type comments (3594)

Integrations

- 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)

Documentation

- Document that only the most recent release is supported for security issues;
vulnerabilities should be reported through Tidelift (3612)