[fixfon]

Fixes #29395.

Both fixes rewrote the else: line and silently dropped any comment after the colon. Following review, the fix no longer tries to move that comment. Instead, PLR5501 and PLW0120 now mark the fix as unsafe when the else: line has a comment that would be deleted, the same approach as UP035 (#29413). Without such a comment the fix stays safe. Inline bodies like else: x = 1 # c also stay safe, since only else: is removed and the comment belongs to the statement.

Both rules got a "Fix safety" section in their docs. The existing PLW0120 snapshots only gain the unsafe-fix note, because their fixtures use else: # [useless-else-on-loop]. New fixture cases cover the unsafe and safe paths for both rules.

I used an AI assistant while working on this and reviewed the changes myself.

[astral-sh-bot]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check detected linter changes. (+0 -0 violations, +0 -2 fixes in 1 projects; 57 projects unchanged)

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

- src/prefect/utilities/pydantic.py:274:5: PLW0120 [*] `else` clause on loop without a `break` statement; remove the `else` and dedent its contents
+ src/prefect/utilities/pydantic.py:274:5: PLW0120 `else` clause on loop without a `break` statement; remove the `else` and dedent its contents

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
PLW0120	2	0	0	0	2

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+1 -1 violations, +0 -0 fixes in 1 projects; 57 projects unchanged)

prefecthq/prefect (+1 -1 violations, +0 -0 fixes)

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

- src/prefect/utilities/pydantic.py:274:5: useless-else-on-loop [*] `else` clause on loop without a `break` statement; remove the `else` and dedent its contents
+ src/prefect/utilities/pydantic.py:274:5: useless-else-on-loop `else` clause on loop without a `break` statement; remove the `else` and dedent its contents

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
useless-else-on-loop	2	1	1	0	0

[ntBre]

Thanks for looking into this! The changes aren't that involved, but I'm kind of leaning toward just marking the fixes unsafe if they would drop comments, instead of trying to retain them. The bit about breaking noqa comments by moving them seems especially unfortunate, even if that already happens in the RET rules. These also seem like fairly niche places to have comments, so just marking them unsafe seems fine.

[fixfon]

Thanks, that makes sense. I removed the comment-moving logic. Both PLR5501 and PLW0120 now mark the fix as unsafe when it would delete a comment on the else: line, and stay safe otherwise. The PLW0120 snapshots are back to their original output, apart from the added unsafe-fix note, since those fixtures have a comment on the else: line. I also added fixture cases for the unsafe and safe paths.

[ntBre]

Thanks!