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Speed up flake8-async by telling libcst to skip deepcopy. #438

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Speed up flake8-async by telling libcst to skip deepcopy. #438

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Speed up flake8-async by telling libcst to skip deepcopy.
yilei Apr 1, 2026
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[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Apr 3, 2026
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9 changes: 8 additions & 1 deletion flake8_async/runner.py
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Original file line number Diff line number Diff line change
Expand Up @@ -138,7 +138,14 @@ def __init__(self, options: Options, module: Module):

def run(self) -> Iterable[Error]:
for v in (*self.utility_visitors, *self.visitors):
self.module = cst.MetadataWrapper(self.module).visit(v)
# The default deepcopy guards against the same CST node object
# appearing at two positions in the tree (metadata is keyed by node
# identity). Parser output and the result of a prior .visit() never
# share nodes, so the copy is wasted work. This stays safe as long
# as no visitor returns a cached CST node from multiple leave_* calls.
self.module = cst.MetadataWrapper(self.module, unsafe_skip_copy=True).visit(
v
)

yield from self.state.problems

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