[pylint] Implement len-test (PLC1802)

[Lokejoke]

Summary

This PR implements use-implicit-booleaness-not-len / C1802

For sequences, (strings, lists, tuples), use the fact that empty sequences are false.

Test Plan

Checked against pylint tests:

• I would argue some of the tests (commented out) are not very intuitive and thus not helpful

Notes

• Naming: Rule name and its error message (adopted from pylint) do not follow conventions used in Ruff (len-as-condition might be solution)

References

PEP 8 on empty sequences and implicit booleaness

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+21 -0 violations, +0 -0 fixes in 6 projects; 49 projects unchanged)

apache/airflow (+7 -0 violations, +0 -0 fixes)

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

+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1639:8: PLC1802 [*] `len(success_entries)` used as condition without comparison
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1646:8: PLC1802 [*] `len(skipped_entries)` used as condition without comparison
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1751:12: PLC1802 [*] `len(success_entries)` used as condition without comparison
+ dev/breeze/src/airflow_breeze/commands/release_management_commands.py:1758:12: PLC1802 [*] `len(skipped_entries)` used as condition without comparison
+ providers/src/airflow/providers/amazon/aws/hooks/glue.py:264:16: PLC1802 [*] `len(fetched_logs)` used as condition without comparison
+ providers/src/airflow/providers/sftp/sensors/sftp.py:129:16: PLC1802 [*] `len(files_found)` used as condition without comparison
+ providers/src/airflow/providers/snowflake/operators/snowflake.py:560:20: PLC1802 [*] `len(queries_in_progress)` used as condition without comparison

apache/superset (+5 -0 violations, +0 -0 fixes)

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

+ superset/databases/filters.py:98:16: PLC1802 [*] `len(allowed_schemas)` used as condition without comparison
+ superset/migrations/versions/2018-07-22_11-59_bebcf3fed1fe_convert_dashboard_v1_positions.py:444:61: PLC1802 [*] `len(SEQUENCE)` used as condition without comparison
+ superset/migrations/versions/2018-07-22_11-59_bebcf3fed1fe_convert_dashboard_v1_positions.py:546:11: PLC1802 [*] `len(ordered_raw_positions)` used as condition without comparison
+ superset/migrations/versions/2018-07-22_11-59_bebcf3fed1fe_convert_dashboard_v1_positions.py:559:16: PLC1802 [*] `len(available_columns_index)` used as condition without comparison
+ superset/migrations/versions/2018-11-12_13-31_4ce8df208545_migrate_time_range_for_default_filters.py:68:24: PLC1802 [*] `len(keys)` used as condition without comparison

bokeh/bokeh (+1 -0 violations, +0 -0 fixes)

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

+ src/bokeh/core/validation/check.py:216:27: PLC1802 [*] `len(warnings)` used as condition without comparison

zulip/zulip (+2 -0 violations, +0 -0 fixes)

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

+ zerver/views/invite.py:127:8: PLC1802 [*] `len(streams)` used as condition without comparison
+ zerver/views/invite.py:243:8: PLC1802 [*] `len(streams)` used as condition without comparison

pytest-dev/pytest (+1 -0 violations, +0 -0 fixes)

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

+ testing/_py/test_local.py:218:16: PLC1802 [*] `len(lst)` used as condition without comparison

astropy/astropy (+5 -0 violations, +0 -0 fixes)

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

+ astropy/io/ascii/misc.py:83:12: PLC1802 [*] `len(first)` used as condition without comparison
+ astropy/units/core.py:1341:16: PLC1802 [*] `len(subresults)` used as condition without comparison
+ astropy/units/core.py:2501:12: PLC1802 [*] `len(names)` used as condition without comparison
+ astropy/wcs/wcs.py:2950:16: PLC1802 [*] `len(missing_keys)` used as condition without comparison
+ astropy/wcs/wcs.py:3765:20: PLC1802 [*] `len(content)` used as condition without comparison

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
PLC1802	21	21	0	0	0

[dylwil3]

Thanks so much for this contribution! Some minor nits/requests for a few more tests. I also didn't get a chance to review the implementation carefully, but I'll hold off for now in case the new tests inspire any changes.

[dylwil3]

This looks really great, thank you! I think even with the possible misses around control flow, this makes sense to implement. You would have to be pretty pathological to create a custom class C that implements __len__ and __bool__ where bool(x) != bool(len(x)) for x: C... so I think it's okay.

[dylwil3]

Almost there! Looking good!

[MichaReiser]

Naming: Maybe len-test to align with https://docs.astral.sh/ruff/rules/not-in-test/#not-in-test-e713

[dylwil3]

LGTM, thank you for the great contribution and your patience through all the reviews!