[flake8-bugbear] Fix break/continue handling in loop-iterator-mutation (B909) - #24440
#24440Merged
MichaReiser merged 5 commits intoApr 21, 2026
astral-sh:mainastral-sh/ruff:mainfrom
anishgirianish:fix/b909-break-continue-branch-trackinganishgirianish/ruff:fix/b909-break-continue-branch-trackingCopy head branch name to clipboard
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[flake8-bugbear] Fix break/continue handling in loop-iterator-mutation (B909)#24440MichaReiser merged 5 commits intoastral-sh:mainastral-sh/ruff:mainfrom anishgirianish:fix/b909-break-continue-branch-trackinganishgirianish/ruff:fix/b909-break-continue-branch-trackingCopy head branch name to clipboard
break/continue handling in loop-iterator-mutation (B909)#24440MichaReiser merged 5 commits into
astral-sh:mainastral-sh/ruff:mainfrom
anishgirianish:fix/b909-break-continue-branch-trackinganishgirianish/ruff:fix/b909-break-continue-branch-trackingCopy head branch name to clipboard
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| code | total | + violation | - violation | + fix | - fix |
|---|---|---|---|---|---|
| B909 | 2 | 0 | 2 | 0 | 0 |
MichaReiser
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Apr 8, 2026
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@MichaReiser Thank you so much for the review. Addressed both comments, nested break/continue is now gated by loop depth, and branch tracking covers for/else, while/else, and try/except/else/finally. Ready for re-review whenever you have time! Thank you |
ntBre
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April 13, 2026 13:37
break/continue handling in loop-iterator-mutation (B909)
MichaReiser
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Thank you. I found one more false positive which we should fix if it's easy to do so. If not, that's fine also.
This PR is certainly a big improvement!
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##### [\`v0.15.12\`](https://github.com/astral-sh/ruff/blob/HEAD/CHANGELOG.md#01512) Released on 2026-04-24. ##### Preview features - Implement `#ruff:file-ignore` file-level suppressions ([#23599](astral-sh/ruff#23599)) - Implement `#ruff:ignore` logical-line suppressions ([#23404](astral-sh/ruff#23404)) - Revert preview changes to displayed diagnostic severity in LSP ([#24789](astral-sh/ruff#24789)) - \[`airflow`] Implement `task-branch-as-short-circuit` (`AIR004`) ([#23579](astral-sh/ruff#23579)) - \[`flake8-bugbear`] Fix `break`/`continue` handling in `loop-iterator-mutation` (`B909`) ([#24440](astral-sh/ruff#24440)) - \[`pylint`] Fix `PLC2701` for type parameter scopes ([#24576](astral-sh/ruff#24576)) ##### Rule changes - \[`pandas-vet`] Suggest `.array` as well in `PD011` ([#24805](astral-sh/ruff#24805)) ##### CLI - Respect default Unix permissions for cache files ([#24794](astral-sh/ruff#24794)) ##### Documentation - \[`pylint`] Fix `PLR0124` description not to claim self-comparison always returns the same value ([#24749](astral-sh/ruff#24749)) - \[`pyupgrade`] Expand docs on reusable `TypeVar`s and scoping (`UP046`) ([#24153](astral-sh/ruff#24153)) - Improve rules table accessibility ([#24711](astral-sh/ruff#24711)) ##### Contributors - [@dylwil3](https://github.com/dylwil3) - [@AlexWaygood](https://github.com/AlexWaygood) - [@woodruffw](https://github.com/woodruffw) - [@avasis-ai](https://github.com/avasis-ai) - [@Dev-iL](https://github.com/Dev-iL) - [@denyszhak](https://github.com/denyszhak) - [@ShipItAndPray](https://github.com/ShipItAndPray) - [@anishgirianish](https://github.com/anishgirianish) - [@augustelalande](https://github.com/augustelalande) - [@amyreese](https://github.com/amyreese) - [@majiayu000](https://github.com/majiayu000) ##### [\`v0.15.11\`](https://github.com/astral-sh/ruff/blob/HEAD/CHANGELOG.md#01511) Released on 2026-04-16. ##### Preview features - \[`ruff`] Ignore `RUF029` when function is decorated with `asynccontextmanager` ([#24642](astral-sh/ruff#24642)) - \[`airflow`] Implement `airflow-xcom-pull-in-template-string` (`AIR201`) ([#23583](astral-sh/ruff#23583)) - \[`flake8-bandit`] Fix `S103` false positives and negatives in mask analysis ([#24424](astral-sh/ruff#24424)) ##### Bug fixes - \[`flake8-async`] Omit overridden methods for `ASYNC109` ([#24648](astral-sh/ruff#24648)) ##### Documentation - \[`flake8-async`] Add override mention to `ASYNC109` docs ([#24666](astral-sh/ruff#24666)) - Update Neovim config examples to use `vim.lsp.config` ([#24577](astral-sh/ruff#24577)) ##### Contributors - [@augustelalande](https://github.com/augustelalande) - [@anishgirianish](https://github.com/anishgirianish) - [@benberryallwood](https://github.com/benberryallwood) - [@charliermarsh](https://github.com/charliermarsh) - [@Dev-iL](https://github.com/Dev-iL) Renovate-Branch: renovate/2024.6-ruff-0.15.x Change-Id: I2c5de44f14ce3133db71161eae18c7b43f7ba09b Priv-Id: 9c1a7f10043a2db2338a90de9a62a4d7989df14d
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Summary
Fixes #12402.
B909's branch tracking had a few issues: the branch counter wasn't restored after if blocks, continue wasn't handled as a terminator, nested loop break/continue was incorrectly treated as exiting the outer loop, and there was no branch isolation for for/else, while/else, or try/except/else/finally.
Fixed by tracking loop_depth so nested break only affects the inner loop, giving each arm of forking statements its own branch (merged back into the parent on exit), and pre-scanning loop bodies to determine whether else is unconditional.
Test Plan
Added 8 fixture cases covering nested break/continue, for/else, while/else, and try/except/else/finally.