[flake8-bugbear] Fix B023 false positive for immediately-invoked lambdas#23294
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charliermarsh merged 1 commit intoastral-sh:mainfrom Feb 16, 2026
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[flake8-bugbear] Fix B023 false positive for immediately-invoked lambdas#23294charliermarsh merged 1 commit intoastral-sh:mainfrom
charliermarsh merged 1 commit intoastral-sh:mainfrom
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* main: (43 commits) [`ruff`] Suppress diagnostic for strings with backslashes in interpolations before Python 3.12 (`RUF027`) (#21069) [flake8-bugbear] Fix B023 false positive for immediately-invoked lambdas (#23294) [ty] Add `Final` mdtests for loops and redeclaration (#23331) [`flake8-pyi`] Also check string annotations (`PYI041`) (#19023) Remove AlexWaygood as a flake8-pyi codeowner (#23347) [ty] Add comments to clarify the purpose of `NominalInstanceType::class_name` and `NominalInstanceType::class_module_name` (#23339) Add attestations for release artifacts and Docker images (#23111) [ty] Fix `assert_type` diagnostic messages (#23342) [ty] Force-update all insta snapshots (#23343) Add Q004 to the list of conflicting rules (#23340) [ty] Fix `invalid-match-pattern` false positives (#23338) [ty] new diagnostic called-match-pattern-must-be-a-type (#22939) [ty] Update flaky projects (#23337) [ty] Increase timeout for ecosystem report to 40 min (#23336) Bump ecosystem-analyzer pin (#23335) [ty] Replace `strsim` with CPython-based Levenshtein implementation (#23291) [ty] Add mdtest for staticmethod assigned in class body (#23330) [ty] fix inferring type variable from string literal argument (#23326) [ty] bytes literal is a sequence of integers (#23329) Update rand and getrandom (#23333) ...
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Summary
Fixes #7847.
B023 (
function-uses-loop-variable) currently flags lambdas that reference loop variables even when the lambda is immediately invoked (IIFE pattern). Since the closure is consumed right away, late-binding is not a concern and the diagnostic is a false positive.This PR marks immediately-invoked lambdas as safe by checking
func.is_lambda_expr()at the call site visitor, pushing the lambda intosafe_functionsso its body is not flagged.Test Plan
Added test cases to
B023.pycovering several IIFE patterns:All existing B023 tests continue to pass. No snapshot changes needed (the new cases produce no diagnostics, as expected).