[flake8-simplify] Implement enumerate-for-loop (SIM113)

[chammika-become]

Implements SIM113 from #998

Added tests
Limitations

• No fix yet
• Only flag cases where index variable immediately precede for loop

@charliermarsh please review and let me know any improvements

[konstin]

good test cases!

[konstin]

Suggested change

	/// idx += 1
	/// idx += 1

[danieleades]

any progress on this?

[charliermarsh]

@danieleades - Na, but I can take it over.

[codspeed-hq]

CodSpeed Performance Report

Merging #7777 will degrade performances by 4.35%

_{Comparing chammika-become:simplify-SIM113 (5c25d68) with main (b6ce4f5)}

Summary

❌ 1 regressions
✅ 29 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	chammika-become:simplify-SIM113	Change
❌	parser[numpy/ctypeslib.py]	12.2 ms	12.8 ms	-4.35%

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+14 -0 violations, +0 -0 fixes in 2 projects; 41 projects unchanged)

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

ruff check --no-cache --exit-zero --preview --select ALL

+ airflow/cli/commands/webserver_command.py:171:13: SIM113 Use `enumerate()` for index variable `excess` in `for` loop
+ airflow/providers/google/cloud/transfers/cassandra_to_gcs.py:180:13: SIM113 Use `enumerate()` for index variable `counter` in `for` loop
+ airflow/providers/google/cloud/transfers/sql_to_gcs.py:202:13: SIM113 Use `enumerate()` for index variable `counter` in `for` loop
+ scripts/ci/pre_commit/pre_commit_update_providers_dependencies.py:317:9: SIM113 Use `enumerate()` for index variable `line_count` in `for` loop

zulip/zulip (+10 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --preview --select ALL

+ zerver/data_import/import_util.py:643:13: SIM113 Use `enumerate()` for index variable `count` in `for` loop
+ zerver/data_import/slack.py:634:9: SIM113 Use `enumerate()` for index variable `recipient_id_count` in `for` loop
+ zerver/data_import/slack.py:635:9: SIM113 Use `enumerate()` for index variable `subscription_id_count` in `for` loop
+ zerver/data_import/slack.py:745:13: SIM113 Use `enumerate()` for index variable `_counter` in `for` loop
+ zerver/lib/export.py:1744:9: SIM113 Use `enumerate()` for index variable `count` in `for` loop
+ zerver/lib/export.py:1865:9: SIM113 Use `enumerate()` for index variable `count` in `for` loop
+ zerver/lib/import_realm.py:791:9: SIM113 Use `enumerate()` for index variable `count` in `for` loop
+ zerver/migrations/0177_user_message_add_and_index_is_private_flag.py:42:9: SIM113 Use `enumerate()` for index variable `i` in `for` loop
+ zerver/tests/test_message_edit.py:1012:13: SIM113 Use `enumerate()` for index variable `i` in `for` loop
+ zilencer/management/commands/populate_db.py:705:17: SIM113 Use `enumerate()` for index variable `i` in `for` loop

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
SIM113	14	14	0	0	0

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[charliermarsh]

(Taking over.)

[danieleades]

@danieleades - Na, but I can take it over.

I only ask because I think this lint is the last hold-out for deprecating flake8 linting from the sphinx project!

[charliermarsh]

😲 😲 😲

[charliermarsh]

Should be good to go, also addressed some false positives that exist in the upstream implementation.

[charliermarsh]

Looking at the ecosystem checks, there are a few more false positives we can fix here.

[charliermarsh]

Namely:

• Ensure that the initialization and the for loop have the same parent (not just the same branch).
• If the variable is used after the loop, consider allowing it? As in:

count = 0
for entry in result:
    assert 'thing' in entry[0]
    count += 1
assert count == 9, 'only 9 query ranges should remain in the DB'

There's a lot of this in tests, which seems ok? I could go either way. You can also write as:

for count, entry in enumerate(result):
    assert 'thing' in entry[0]
assert count == 9, 'only 9 query ranges should remain in the DB'