Ruff

Preview features

- Formatter: Avoid invalid syntax for format-spec with quotes for all Python versions ([14625](https://github.com/astral-sh/ruff/pull/14625))
- Formatter: Consider quotes inside format-specs when choosing the quotes for an f-string ([14493](https://github.com/astral-sh/ruff/pull/14493))
- Formatter: Do not consider f-strings with escaped newlines as multiline ([14624](https://github.com/astral-sh/ruff/pull/14624))
- Formatter: Fix f-string formatting in assignment statement ([14454](https://github.com/astral-sh/ruff/pull/14454))
- Formatter: Fix unnecessary space around power operator (`**`) in overlong f-string expressions ([14489](https://github.com/astral-sh/ruff/pull/14489))
- \[`airflow`\] Avoid implicit `schedule` argument to `DAG` and `dag` (`AIR301`) ([14581](https://github.com/astral-sh/ruff/pull/14581))
- \[`flake8-builtins`\] Exempt private built-in modules (`A005`) ([14505](https://github.com/astral-sh/ruff/pull/14505))
- \[`flake8-pytest-style`\] Fix `pytest.mark.parametrize` rules to check calls instead of decorators ([14515](https://github.com/astral-sh/ruff/pull/14515))
- \[`flake8-type-checking`\] Implement `runtime-cast-value` (`TC006`) ([14511](https://github.com/astral-sh/ruff/pull/14511))
- \[`flake8-type-checking`\] Implement `unquoted-type-alias` (`TC007`) and `quoted-type-alias` (`TC008`) ([12927](https://github.com/astral-sh/ruff/pull/12927))
- \[`flake8-use-pathlib`\] Recommend `Path.iterdir()` over `os.listdir()` (`PTH208`) ([14509](https://github.com/astral-sh/ruff/pull/14509))
- \[`pylint`\] Extend `invalid-envvar-default` to detect `os.environ.get` (`PLW1508`) ([14512](https://github.com/astral-sh/ruff/pull/14512))
- \[`pylint`\] Implement `len-test` (`PLC1802`) ([14309](https://github.com/astral-sh/ruff/pull/14309))
- \[`refurb`\] Fix bug where methods defined using lambdas were flagged by `FURB118` ([14639](https://github.com/astral-sh/ruff/pull/14639))
- \[`ruff`\] Auto-add `r` prefix when string has no backslashes for `unraw-re-pattern` (`RUF039`) ([14536](https://github.com/astral-sh/ruff/pull/14536))
- \[`ruff`\] Implement `invalid-assert-message-literal-argument` (`RUF040`) ([14488](https://github.com/astral-sh/ruff/pull/14488))
- \[`ruff`\] Implement `unnecessary-nested-literal` (`RUF041`) ([14323](https://github.com/astral-sh/ruff/pull/14323))
- \[`ruff`\] Implement `unnecessary-regular-expression` (`RUF055`) ([14659](https://github.com/astral-sh/ruff/pull/14659))

Rule changes

- Ignore more rules for stub files ([14541](https://github.com/astral-sh/ruff/pull/14541))
- \[`pep8-naming`\] Eliminate false positives for single-letter names (`N811`, `N814`) ([14584](https://github.com/astral-sh/ruff/pull/14584))
- \[`pyflakes`\] Avoid false positives in `no_type_check` contexts (`F821`, `F722`) ([14615](https://github.com/astral-sh/ruff/pull/14615))
- \[`ruff`\] Detect redirected-noqa in file-level comments (`RUF101`) ([14635](https://github.com/astral-sh/ruff/pull/14635))
- \[`ruff`\] Mark fixes for `unsorted-dunder-all` and `unsorted-dunder-slots` as unsafe when there are complex comments in the sequence (`RUF022`, `RUF023`) ([14560](https://github.com/astral-sh/ruff/pull/14560))

Bug fixes

- Avoid fixing code to `None | None` for `redundant-none-literal` (`PYI061`) and `never-union` (`RUF020`) ([14583](https://github.com/astral-sh/ruff/pull/14583), [#14589](https://github.com/astral-sh/ruff/pull/14589))
- \[`flake8-bugbear`\] Fix `mutable-contextvar-default` to resolve annotated function calls properly (`B039`) ([14532](https://github.com/astral-sh/ruff/pull/14532))
- \[`flake8-pyi`, `ruff`\] Fix traversal of nested literals and unions (`PYI016`, `PYI051`, `PYI055`, `PYI062`, `RUF041`) ([14641](https://github.com/astral-sh/ruff/pull/14641))
- \[`flake8-pyi`\] Avoid rewriting invalid type expressions in `unnecessary-type-union` (`PYI055`) ([14660](https://github.com/astral-sh/ruff/pull/14660))
- \[`flake8-type-checking`\] Avoid syntax errors and type checking problem for quoted annotations autofix (`TC003`, `TC006`) ([14634](https://github.com/astral-sh/ruff/pull/14634))
- \[`pylint`\] Do not wrap function calls in parentheses in the fix for unnecessary-dunder-call (`PLC2801`) ([14601](https://github.com/astral-sh/ruff/pull/14601))
- \[`ruff`\] Handle `attrs`'s `auto_attribs` correctly (`RUF009`) ([14520](https://github.com/astral-sh/ruff/pull/14520))

- **Default to Python 3.9**

Ruff now defaults to Python 3.9 instead of 3.8 if no explicit Python version is configured using [`ruff.target-version`](https://docs.astral.sh/ruff/settings/#target-version) or [`project.requires-python`](https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#python-requires) ([13896](https://github.com/astral-sh/ruff/pull/13896))

- **Changed location of `pydoclint` diagnostics**

[`pydoclint`](https://docs.astral.sh/ruff/rules/#pydoclint-doc) diagnostics now point to the first-line of the problematic docstring. Previously, this was not the case.

If you've opted into these preview rules but have them suppressed using
[`noqa`](https://docs.astral.sh/ruff/linter/#error-suppression) comments in
some places, this change may mean that you need to move the `noqa` suppression
comments. Most users should be unaffected by this change.

- **Use XDG (i.e. `~/.local/bin`) instead of the Cargo home directory in the standalone installer**

Previously, Ruff's installer used `$CARGO_HOME` or `~/.cargo/bin` for its target install directory. Now, Ruff will be installed into `$XDG_BIN_HOME`, `$XDG_DATA_HOME/../bin`, or `~/.local/bin` (in that order).

This change is only relevant to users of the standalone Ruff installer (using the shell or PowerShell script). If you installed Ruff using uv or pip, you should be unaffected.

- **Changes to the line width calculation**

Ruff now uses a new version of the [unicode-width](https://github.com/unicode-rs/unicode-width) Rust crate to calculate the line width. In very rare cases, this may lead to lines containing Unicode characters being reformatted, or being considered too long when they were not before ([`E501`](https://docs.astral.sh/ruff/rules/line-too-long/)).

Preview features

- \[`flake8-datetimez`\] Detect usages of `datetime.max`/`datetime.min` (`DTZ901`) ([14288](https://github.com/astral-sh/ruff/pull/14288))
- \[`flake8-logging`\] Implement `root-logger-calls` (`LOG015`) ([14302](https://github.com/astral-sh/ruff/pull/14302))
- \[`flake8-no-pep420`\] Detect empty implicit namespace packages (`INP001`) ([14236](https://github.com/astral-sh/ruff/pull/14236))
- \[`flake8-pyi`\] Add "replace with `Self`" fix (`PYI019`) ([14238](https://github.com/astral-sh/ruff/pull/14238))
- \[`perflint`\] Implement quick-fix for `manual-list-comprehension` (`PERF401`) ([13919](https://github.com/astral-sh/ruff/pull/13919))
- \[`pylint`\] Implement `shallow-copy-environ` (`W1507`) ([14241](https://github.com/astral-sh/ruff/pull/14241))
- \[`ruff`\] Implement `none-not-at-end-of-union` (`RUF036`) ([14314](https://github.com/astral-sh/ruff/pull/14314))
- \[`ruff`\] Implementation `unsafe-markup-call` from `flake8-markupsafe` plugin (`RUF035`) ([14224](https://github.com/astral-sh/ruff/pull/14224))
- \[`ruff`\] Report problems for `attrs` dataclasses (`RUF008`, `RUF009`) ([14327](https://github.com/astral-sh/ruff/pull/14327))

Rule changes

- \[`flake8-boolean-trap`\] Exclude dunder methods that define operators (`FBT001`) ([14203](https://github.com/astral-sh/ruff/pull/14203))
- \[`flake8-pyi`\] Add "replace with `Self`" fix (`PYI034`) ([14217](https://github.com/astral-sh/ruff/pull/14217))
- \[`flake8-pyi`\] Always autofix `duplicate-union-members` (`PYI016`) ([14270](https://github.com/astral-sh/ruff/pull/14270))
- \[`flake8-pyi`\] Improve autofix for nested and mixed type unions for `unnecessary-type-union` (`PYI055`) ([14272](https://github.com/astral-sh/ruff/pull/14272))
- \[`flake8-pyi`\] Mark fix as unsafe when type annotation contains comments for `duplicate-literal-member` (`PYI062`) ([14268](https://github.com/astral-sh/ruff/pull/14268))

Server

- Use the current working directory to resolve settings from `ruff.configuration` ([14352](https://github.com/astral-sh/ruff/pull/14352))

Bug fixes

- Avoid conflicts between `PLC014` (`useless-import-alias`) and `I002` (`missing-required-import`) by considering `lint.isort.required-imports` for `PLC014` ([14287](https://github.com/astral-sh/ruff/pull/14287))
- \[`flake8-type-checking`\] Skip quoting annotation if it becomes invalid syntax (`TCH001`)
- \[`flake8-pyi`\] Avoid using `typing.Self` in stub files pre-Python 3.11 (`PYI034`) ([14230](https://github.com/astral-sh/ruff/pull/14230))
- \[`flake8-pytest-style`\] Flag `pytest.raises` call with keyword argument `expected_exception` (`PT011`) ([14298](https://github.com/astral-sh/ruff/pull/14298))
- \[`flake8-simplify`\] Infer "unknown" truthiness for literal iterables whose items are all unpacks (`SIM222`) ([14263](https://github.com/astral-sh/ruff/pull/14263))
- \[`flake8-type-checking`\] Fix false positives for `typing.Annotated` (`TCH001`) ([14311](https://github.com/astral-sh/ruff/pull/14311))
- \[`pylint`\] Allow `await` at the top-level scope of a notebook (`PLE1142`) ([14225](https://github.com/astral-sh/ruff/pull/14225))
- \[`pylint`\] Fix miscellaneous issues in `await-outside-async` detection (`PLE1142`) ([14218](https://github.com/astral-sh/ruff/pull/14218))
- \[`pyupgrade`\] Avoid applying PEP 646 rewrites in invalid contexts (`UP044`) ([14234](https://github.com/astral-sh/ruff/pull/14234))
- \[`pyupgrade`\] Detect permutations in redundant open modes (`UP015`) ([14255](https://github.com/astral-sh/ruff/pull/14255))
- \[`refurb`\] Avoid triggering `hardcoded-string-charset` for reordered sets (`FURB156`) ([14233](https://github.com/astral-sh/ruff/pull/14233))
- \[`refurb`\] Further special cases added to `verbose-decimal-constructor` (`FURB157`) ([14216](https://github.com/astral-sh/ruff/pull/14216))
- \[`refurb`\] Use `UserString` instead of non-existent `UserStr` (`FURB189`) ([14209](https://github.com/astral-sh/ruff/pull/14209))
- \[`ruff`\] Avoid treating lowercase letters as ` noqa` codes (`RUF100`) ([14229](https://github.com/astral-sh/ruff/pull/14229))
- \[`ruff`\] Do not report when `Optional` has no type arguments (`RUF013`) ([14181](https://github.com/astral-sh/ruff/pull/14181))

Documentation

- Add "Notebook behavior" section for `F704`, `PLE1142` ([14266](https://github.com/astral-sh/ruff/pull/14266))
- Document comment policy around fix safety ([14300](https://github.com/astral-sh/ruff/pull/14300))

Preview features

- Formatter: Disallow single-line implicit concatenated strings ([13928](https://github.com/astral-sh/ruff/pull/13928))
- \[`flake8-pyi`\] Include all Python file types for `PYI006` and `PYI066` ([14059](https://github.com/astral-sh/ruff/pull/14059))
- \[`flake8-simplify`\] Implement `split-of-static-string` (`SIM905`) ([14008](https://github.com/astral-sh/ruff/pull/14008))
- \[`refurb`\] Implement `subclass-builtin` (`FURB189`) ([14105](https://github.com/astral-sh/ruff/pull/14105))
- \[`ruff`\] Improve diagnostic messages and docs (`RUF031`, `RUF032`, `RUF034`) ([14068](https://github.com/astral-sh/ruff/pull/14068))

Rule changes

- Detect items that hash to same value in duplicate sets (`B033`, `PLC0208`) ([14064](https://github.com/astral-sh/ruff/pull/14064))
- \[`eradicate`\] Better detection of IntelliJ language injection comments (`ERA001`) ([14094](https://github.com/astral-sh/ruff/pull/14094))
- \[`flake8-pyi`\] Add autofix for `docstring-in-stub` (`PYI021`) ([14150](https://github.com/astral-sh/ruff/pull/14150))
- \[`flake8-pyi`\] Update `duplicate-literal-member` (`PYI062`) to alawys provide an autofix ([14188](https://github.com/astral-sh/ruff/pull/14188))
- \[`pyflakes`\] Detect items that hash to same value in duplicate dictionaries (`F601`) ([14065](https://github.com/astral-sh/ruff/pull/14065))
- \[`ruff`\] Fix false positive for decorators (`RUF028`) ([14061](https://github.com/astral-sh/ruff/pull/14061))

Bug fixes

- Avoid parsing joint rule codes as distinct codes in ` noqa` ([12809](https://github.com/astral-sh/ruff/pull/12809))
- \[`eradicate`\] ignore ` language=` in commented-out-code rule (ERA001) ([14069](https://github.com/astral-sh/ruff/pull/14069))
- \[`flake8-bugbear`\] - do not run `mutable-argument-default` on stubs (`B006`) ([14058](https://github.com/astral-sh/ruff/pull/14058))
- \[`flake8-builtins`\] Skip lambda expressions in `builtin-argument-shadowing (A002)` ([14144](https://github.com/astral-sh/ruff/pull/14144))
- \[`flake8-comprehension`\] Also remove trailing comma while fixing `C409` and `C419` ([14097](https://github.com/astral-sh/ruff/pull/14097))
- \[`flake8-simplify`\] Allow `open` without context manager in `return` statement (`SIM115`) ([14066](https://github.com/astral-sh/ruff/pull/14066))
- \[`pylint`\] Respect hash-equivalent literals in `iteration-over-set` (`PLC0208`) ([14063](https://github.com/astral-sh/ruff/pull/14063))
- \[`pylint`\] Update known dunder methods for Python 3.13 (`PLW3201`) ([14146](https://github.com/astral-sh/ruff/pull/14146))
- \[`pyupgrade`\] - ignore kwarg unpacking for `UP044` ([14053](https://github.com/astral-sh/ruff/pull/14053))
- \[`refurb`\] Parse more exotic decimal strings in `verbose-decimal-constructor` (`FURB157`) ([14098](https://github.com/astral-sh/ruff/pull/14098))

Documentation

- Add links to missing related options within rule documentations ([13971](https://github.com/astral-sh/ruff/pull/13971))
- Add rule short code to mkdocs tags to allow searching via rule codes ([14040](https://github.com/astral-sh/ruff/pull/14040))

Preview features

- Fix formatting of single with-item with trailing comment ([14005](https://github.com/astral-sh/ruff/pull/14005))
- \[`pyupgrade`\] Add PEP 646 `Unpack` conversion to `*` with fix (`UP044`) ([13988](https://github.com/astral-sh/ruff/pull/13988))

Rule changes

- Regenerate `known_stdlibs.rs` with stdlibs 2024.10.25 ([13963](https://github.com/astral-sh/ruff/pull/13963))
- \[`flake8-no-pep420`\] Skip namespace package enforcement for PEP 723 scripts (`INP001`) ([13974](https://github.com/astral-sh/ruff/pull/13974))

Server

- Fix server panic when undoing an edit ([14010](https://github.com/astral-sh/ruff/pull/14010))

Bug fixes

- Fix issues in discovering ruff in pip build environments ([13881](https://github.com/astral-sh/ruff/pull/13881))
- \[`flake8-type-checking`\] Fix false positive for `singledispatchmethod` (`TCH003`) ([13941](https://github.com/astral-sh/ruff/pull/13941))
- \[`flake8-type-checking`\] Treat return type of `singledispatch` as runtime-required (`TCH003`) ([13957](https://github.com/astral-sh/ruff/pull/13957))

Documentation

- \[`flake8-simplify`\] Include caveats of enabling `if-else-block-instead-of-if-exp` (`SIM108`) ([14019](https://github.com/astral-sh/ruff/pull/14019))

Preview features

- Fix `E221` and `E222` to flag missing or extra whitespace around `==` operator ([13890](https://github.com/astral-sh/ruff/pull/13890))
- Formatter: Alternate quotes for strings inside f-strings in preview ([13860](https://github.com/astral-sh/ruff/pull/13860))
- Formatter: Join implicit concatenated strings when they fit on a line ([13663](https://github.com/astral-sh/ruff/pull/13663))
- \[`pylint`\] Restrict `iteration-over-set` to only work on sets of literals (`PLC0208`) ([13731](https://github.com/astral-sh/ruff/pull/13731))

Rule changes

- \[`flake8-type-checking`\] Support auto-quoting when annotations contain quotes ([11811](https://github.com/astral-sh/ruff/pull/11811))

Server

- Avoid indexing the workspace for single-file mode ([13770](https://github.com/astral-sh/ruff/pull/13770))

Bug fixes

- Make `ARG002` compatible with `EM101` when raising `NotImplementedError` ([13714](https://github.com/astral-sh/ruff/pull/13714))

Other changes

- Introduce more Docker tags for Ruff (similar to uv) ([13274](https://github.com/astral-sh/ruff/pull/13274))