[refurb] Mark single-item-membership-test fix as always unsafe (FURB171)

[TaKO8Ki]

Summary

Fixes #20255

Mark single-item-membership-test fixes as always unsafe

• Always set Applicability::Unsafe for FURB171 fixes
• Update “Fix safety” docs to reflect always-unsafe behavior
• Expand tests (not in, nested set/frozenset, commented args)

Test Plan

I have added new test cases to crates/ruff_linter/resources/test/fixtures/refurb/FURB171_0.py and crates/ruff_linter/resources/test/fixtures/refurb/FURB171_1.py.

[TaKO8Ki]

Previously, fixes were marked unsafe only for string literals and when comments intersected the edit range, but single‑item list/tuple/set/frozenset cases can also
change behavior (e.g., NaN identity differences and non‑boolean eq), so we now mark all FURB171 fixes as unsafe.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+0 -0 violations, +0 -64 fixes in 5 projects; 50 projects unchanged)

apache/airflow (+0 -0 violations, +0 -44 fixes)

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

+ airflow-core/src/airflow/utils/db.py:1419:8: FURB171 Membership test against single-item container
- airflow-core/src/airflow/utils/db.py:1419:8: FURB171 [*] Membership test against single-item container
+ airflow-core/tests/unit/cli/commands/test_variable_command.py:516:16: FURB171 Membership test against single-item container
- airflow-core/tests/unit/cli/commands/test_variable_command.py:516:16: FURB171 [*] Membership test against single-item container
+ airflow-core/tests/unit/cli/commands/test_variable_command.py:533:16: FURB171 Membership test against single-item container
- airflow-core/tests/unit/cli/commands/test_variable_command.py:533:16: FURB171 [*] Membership test against single-item container
+ dev/breeze/src/airflow_breeze/utils/run_tests.py:427:8: FURB171 Membership test against single-item container
- dev/breeze/src/airflow_breeze/utils/run_tests.py:427:8: FURB171 [*] Membership test against single-item container
+ dev/react-plugin-tools/bootstrap.py:59:10: FURB171 Membership test against single-item container
- dev/react-plugin-tools/bootstrap.py:59:10: FURB171 [*] Membership test against single-item container
+ dev/react-plugin-tools/bootstrap.py:62:10: FURB171 Membership test against single-item container
- dev/react-plugin-tools/bootstrap.py:62:10: FURB171 [*] Membership test against single-item container
+ devel-common/src/docs/provider_conf.py:270:4: FURB171 Membership test against single-item container
- devel-common/src/docs/provider_conf.py:270:4: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:140:103: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:140:103: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:164:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:164:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:186:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:186:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:187:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:187:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:209:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:209:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:210:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:210:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:267:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:267:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:268:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:268:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:278:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:278:31: FURB171 [*] Membership test against single-item container
+ providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:279:31: FURB171 Membership test against single-item container
- providers/common/sql/tests/unit/common/sql/sensors/test_sql.py:279:31: FURB171 [*] Membership test against single-item container
... 10 additional changes omitted for project

apache/superset (+0 -0 violations, +0 -4 fixes)

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

+ superset/connectors/sqla/models.py:796:62: FURB171 Membership test against single-item container
- superset/connectors/sqla/models.py:796:62: FURB171 [*] Membership test against single-item container
+ superset/models/helpers.py:2120:26: FURB171 Membership test against single-item container
- superset/models/helpers.py:2120:26: FURB171 [*] Membership test against single-item container

reflex-dev/reflex (+0 -0 violations, +0 -2 fixes)

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

+ reflex/utils/templates.py:388:34: FURB171 Membership test against single-item container
- reflex/utils/templates.py:388:34: FURB171 [*] Membership test against single-item container

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

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

+ tests/test_settings_overrides.py:441:8: FURB171 Membership test against single-item container
- tests/test_settings_overrides.py:441:8: FURB171 [*] Membership test against single-item container

zulip/zulip (+0 -0 violations, +0 -12 fixes)

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

+ tools/lib/provision.py:155:28: FURB171 Membership test against single-item container
- tools/lib/provision.py:155:28: FURB171 [*] Membership test against single-item container
+ zerver/actions/presence.py:87:8: FURB171 Membership test against single-item container
- zerver/actions/presence.py:87:8: FURB171 [*] Membership test against single-item container
+ zerver/lib/emoji.py:107:12: FURB171 Membership test against single-item container
- zerver/lib/emoji.py:107:12: FURB171 [*] Membership test against single-item container
+ zerver/lib/narrow_predicate.py:60:39: FURB171 Membership test against single-item container
- zerver/lib/narrow_predicate.py:60:39: FURB171 [*] Membership test against single-item container
+ zerver/lib/url_decoding.py:136:30: FURB171 Membership test against single-item container
- zerver/lib/url_decoding.py:136:30: FURB171 [*] Membership test against single-item container
... 2 additional changes omitted for project

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
FURB171	64	0	0	0	64

[ntBre]

Thanks, this looks good! I just had a couple of minor suggestions. I agree with marking the fix as always unsafe instead of trying to look for the few special safe cases mentioned in the issue. I think that could get pretty complicated.

[ntBre]

Thank you! Just a couple of small docs nits that I'll apply and then merge this :)