Add check for single-character alternations (W129) - #57
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Flag alternations whose every branch is a single foldable character and suggest the equivalent character class, which matches faster and reads more clearly: a|b|c -> [abc], \d|_|\. -> [\d_\.], (a|b)c -> [ab]c. Foldable atoms are plain literals, single-char escapes (\., \+, \x41, \\, ...), builtin classes (\d \w \s \D \W \S) and \t/\n. Branches that would change meaning or break the class are left alone: multi-char runs (foo|bar), '.', anchors, groups, quantified atoms (a|b+) and a bare ']'. Includes unit tests for the literal, builtin/escape, nested-in-group and the various no-flag cases.
jvoisin
marked this pull request as draft
July 28, 2026 15:24
jvoisin
marked this pull request as ready for review
July 28, 2026 15:31
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Flag alternations whose every branch is a single foldable character and suggest the equivalent character class, which matches faster and reads more clearly: a|b|c -> [abc], \d||. -> [\d.], (a|b)c -> [ab]c.
Foldable atoms are plain literals, single-char escapes (., +, \x41, \, ...), builtin classes (\d \w \s \D \W \S) and \t/\n. Branches that would change meaning or break the class are left alone: multi-char runs (foo|bar), '.', anchors, groups, quantified atoms (a|b+) and a bare ']'.
Includes unit tests for the literal, builtin/escape, nested-in-group and the various no-flag cases.