[flake8-bugbear] Fix break/continue handling in loop-iterator-mutation (B909)#24440
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MichaReiser merged 5 commits intoastral-sh:mainfrom Apr 21, 2026
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| code | total | + violation | - violation | + fix | - fix |
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| 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 |
break/continue handling in loop-iterator-mutation (B909)
MichaReiser
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Apr 14, 2026
MichaReiser
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Apr 16, 2026
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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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MichaReiser
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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.