Add check for quantified lookaround assertions (W129) - #58
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Flag quantifiers applied to a zero-width lookaround, e.g. (?=a)+, (?!a)*, (?<=a)+, (?=a)?. Repeating a zero-width match is a no-op and making an assertion optional simply disables it, so both are almost always mistakes. Quantified anchors (\b+, ^?) are rejected by the engine at compile time and never reach the linter, so only lookaround groups are checked. Non-quantified lookarounds and quantified real groups ((a)+, (?:a)+) are left alone. Includes unit tests covering all lookaround kinds and quantifier variants, in-context matches and the no-flag cases.
thatch
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Jul 31, 2026
Renumber check_redundant_noncapturing_group from 129 to 133; it collided with checks added by #55-#58 (129-132), since all were written independently against the same base. Also fix test_run_all_checkers_no_errors: it used (?:x) as a baseline 'no errors expected' pattern, but that group is now correctly flagged as redundant by the new check. Switched to a plain 'x' with no group to keep the test's intent.
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Flag quantifiers applied to a zero-width lookaround, e.g. (?=a)+, (?!a)*, (?<=a)+, (?=a)?. Repeating a zero-width match is a no-op and making an assertion optional simply disables it, so both are almost always mistakes.
Quantified anchors (\b+, ^?) are rejected by the engine at compile time and never reach the linter, so only lookaround groups are checked. Non-quantified lookarounds and quantified real groups ((a)+, (?:a)+) are left alone.
Includes unit tests covering all lookaround kinds and quantifier variants, in-context matches and the no-flag cases.