[flake8-pyi] Mark PYI061 fixes unsafe in Python files

[jesco-absolut]

Summary

Closes #20729.

This marks PYI061 fixes as unsafe in non-stub Python files.

The fix can rewrite Literal["foo", "bar", None] into Literal["foo", "bar"] | None. That is equivalent for type checkers, but it is not fully equivalent at runtime: code that introspects annotations with typing.get_args() observes a different structure after the rewrite.

Stub files keep the previous behavior, since they are not runtime Python files: fixes are still safe unless comments are removed.

I also added a regression case to the existing PYI061.py fixture. While updating the snapshots, this also removes trailing whitespace from the affected diagnostic messages.

Test Plan

Reproduced the issue before the change:

cargo run -p ruff -- check /tmp/pyi061_repro.py --select PYI061 --fix --diff --no-cache --isolated

Verified that after the change, the fix is no longer applied by default and is only available with --unsafe-fixes.

Verified that the fix is still available with unsafe fixes enabled:

cargo run -p ruff -- check /tmp/pyi061_repro.py --select PYI061 --fix --diff --unsafe-fixes --no-cache --isolated

Ran the targeted snapshot tests:

CARGO_PROFILE_DEV_OPT_LEVEL=1 INSTA_FORCE_PASS=1 INSTA_UPDATE=always CARGO_PROFILE_DEV_DEBUG="line-tables-only" MDTEST_UPDATE_SNAPSHOTS=1 cargo test -p ruff_linter rule_redundantnoneliteral_path_new_pyi061 -- --nocapture

Also ran:

cargo dev generate-all
uv run --only-group dev --locked prek run --files crates/ruff_linter/resources/test/fixtures/flake8_pyi/PYI061.py crates/ruff_linter/src/rules/flake8_pyi/rules/redundant_none_literal.rs crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__PYI061_PYI061.py.snap crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__PYI061_PYI061.pyi.snap crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__py38_PYI061_PYI061.py.snap crates/ruff_linter/src/rules/flake8_pyi/snapshots/ruff_linter__rules__flake8_pyi__tests__py38_PYI061_PYI061.pyi.snap
git diff --check

[ntBre]

Thank you, this makes sense to me! I just had one suggestion/request about the test location.

[astral-sh-bot]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check detected linter changes. (+2 -2 violations, +0 -0 fixes in 2 projects; 54 projects unchanged)

apache/airflow (+1 -1 violations, +0 -0 fixes)

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

+ airflow-core/src/airflow/serialization/definitions/dag.py:999:36: PYI061 Use `Literal[...] | None` rather than `Literal[None, ...]`
- airflow-core/src/airflow/serialization/definitions/dag.py:999:36: PYI061 [*] Use `Literal[...] | None` rather than `Literal[None, ...]` 

latchbio/latch (+1 -1 violations, +0 -0 fixes)

+ src/latch/types/metadata.py:496:45: PYI061 Use `Optional[Literal[...]]` rather than `Literal[None, ...]`
- src/latch/types/metadata.py:496:45: PYI061 [*] Use `Optional[Literal[...]]` rather than `Literal[None, ...]` 

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
PYI061	4	2	2	0	0

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+4 -4 violations, +0 -0 fixes in 3 projects; 53 projects unchanged)

apache/airflow (+1 -1 violations, +0 -0 fixes)

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

+ airflow-core/src/airflow/serialization/definitions/dag.py:999:36: redundant-none-literal Use `Literal[...] | None` rather than `Literal[None, ...]`
- airflow-core/src/airflow/serialization/definitions/dag.py:999:36: redundant-none-literal [*] Use `Literal[...] | None` rather than `Literal[None, ...]` 

latchbio/latch (+1 -1 violations, +0 -0 fixes)

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

+ src/latch/types/metadata.py:496:45: redundant-none-literal Use `Optional[Literal[...]]` rather than `Literal[None, ...]`
- src/latch/types/metadata.py:496:45: redundant-none-literal [*] Use `Optional[Literal[...]]` rather than `Literal[None, ...]` 

prefecthq/prefect (+2 -2 violations, +0 -0 fixes)

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

+ src/prefect/tasks.py:1882:19: redundant-none-literal Use `None` rather than `Literal[None]`
- src/prefect/tasks.py:1882:19: redundant-none-literal [*] Use `None` rather than `Literal[None]`
+ src/prefect/tasks.py:1919:19: redundant-none-literal Use `None` rather than `Literal[None]`
- src/prefect/tasks.py:1919:19: redundant-none-literal [*] Use `None` rather than `Literal[None]`

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
redundant-none-literal	8	4	4	0	0