[ruff] Implicit class variable in dataclass (RUF045)

[InSyncWithFoo]

Summary

Resolves #12877.

Test Plan

cargo nextest run and cargo insta test.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+8 -0 violations, +0 -0 fixes in 4 projects; 51 projects unchanged)

apache/airflow (+2 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select ALL

+ airflow/executors/base_executor.py:89:5: RUF045 Assignment without annotation found in dataclass body
+ dev/breeze/src/airflow_breeze/params/doc_build_params.py:36:5: RUF045 Assignment without annotation found in dataclass body

latchbio/latch (+3 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

+ src/latch_cli/constants.py:31:5: RUF045 Assignment without annotation found in dataclass body
+ src/latch_cli/constants.py:32:5: RUF045 Assignment without annotation found in dataclass body
+ src/latch_cli/constants.py:39:5: RUF045 Assignment without annotation found in dataclass body

python/typeshed (+1 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select E,F,FA,I,PYI,RUF,UP,W

+ stubs/fpdf2/fpdf/fonts.pyi:33:5: RUF045 Assignment without annotation found in dataclass body

scikit-build/scikit-build-core (+2 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

+ src/scikit_build_core/file_api/model/codemodel.py:129:5: RUF045 Assignment without annotation found in dataclass body
+ src/scikit_build_core/file_api/model/directory.py:23:5: RUF045 Assignment without annotation found in dataclass body

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
RUF045	8	8	0	0	0

[InSyncWithFoo]

False positives found by ecosystem checks:

stubs/fpdf2/fpdf/fonts.pyi (@python/typeshed):

@dataclass
class FontFace:
    family: str | None
    emphasis: TextEmphasis | None
    size_pt: int | None
    color: DeviceGray | DeviceRGB | None
    fill_color: DeviceGray | DeviceRGB | None

    ...

    replace = dataclasses.replace

src/_pytest/fixtures.py (@pytest-dev/pytest):

@dataclasses.dataclass(frozen=True)
class FuncFixtureInfo:
    ...

    __slots__ = ("argnames", "initialnames", "names_closure", "name2fixturedefs")

Special names can be exempted, but I'm not sure what to do about the first.

[MichaReiser]

I'm not saying we shouldn't do it, but requiring type annotations has been controversial in other instances; for example, there's a long thread for RUF012 that does something similar. @AlexWaygood I'd be interested on your take on this before I start reviewing the rule itself.

[dylwil3]

Thank you!

Looking at the ecosystem results, it seems fairly common for users to define a private class variable in their dataclasses. So I've restricted the scope of the rule a little to exempt that.