fix(linter): suppress FURB122 fix when walrus operator rebinds loop variable#24566
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hijingsong wants to merge 1 commit intoastral-sh:mainfrom
Open
fix(linter): suppress FURB122 fix when walrus operator rebinds loop variable#24566hijingsong wants to merge 1 commit intoastral-sh:mainfrom
hijingsong wants to merge 1 commit intoastral-sh:mainfrom
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…ariable
When the argument to `.write()` in a for-loop contains a walrus operator
(:=) whose target is one of the for-loop's iteration variables, the
FURB122 fix would generate an invalid comprehension. For example:
for line in src:
dst.write(line := line.upper())
would be transformed to:
dst.writelines(line := line.upper() for line in src)
which is a SyntaxError because the walrus operator cannot rebind a
comprehension iteration variable.
Suppress the fix in such cases by detecting walrus operators in the
write argument whose targets match any for-loop binding names.
Closes: astral-sh#21107
MichaReiser
reviewed
Apr 13, 2026
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| impl<'a> Visitor<'a> for WalrusChecker<'a> { |
Member
There was a problem hiding this comment.
You can use any_over_expr over writing your own visitor. I also suggest you take a look at the previous PRs trying to fix this issue. Maybe there's some test cases or edge cases that are worth copying over:)
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Summary
Suppresses the FURB122 (
for-loop-writes) fix when the.write()argument contains a walrus operator (:=) whose target is one of the for-loop's iteration variables.The fix would otherwise generate an invalid comprehension. For example:
would be transformed to:
which produces
SyntaxError: assignment expression cannot rebind comprehension iteration variable 'line'.Similarly for tuple unpacking:
Test Plan
Added test cases to
FURB122.pyfixture:dst.write(line := line.upper())wherelineis the loop variabledst.write(rest := "".join(rest))whererestis a loop variable from tuple unpackingf.write(y := process(x))whereyis NOT a loop variable — the fix is still valid hereCloses: #21107