Add check for redundant whitespace alternations - #52
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Flag patterns like (\n|\s+)+, (\n|\s)+ and (\s|\n)+ where an outer +/* repetition wraps a group whose alternation branches all match only whitespace subsumed by \s, with at least one branch being \s itself. Since \s already matches \n (and others), the alternation, group and outer quantifier are all redundant and the pattern simplifies to \s+. This is the anti-pattern cleaned up in pygments/pygments#3186. New checker 126 (check_redundant_whitespace_alternation), with tests.
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Jul 31, 2026
This is the second time independent PRs collided on the same message id (126 across #52/#53/#54, now 129 across #55-#59). Statically walk each check_/bygroups_check_/groups_check_ function's source for its 'num' assignment and assert none repeat, so a future collision fails CI instead of silently shipping ambiguous warning codes.
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Flag patterns like (\n|\s+)+, (\n|\s)+ and (\s|\n)+ where an outer +/* repetition wraps a group whose alternation branches all match only whitespace subsumed by \s, with at least one branch being \s itself. Since \s already matches \n (and others), the alternation, group and outer quantifier are all redundant and the pattern simplifies to \s+.
This is the anti-pattern cleaned up in pygments/pygments#3186.
New checker 126 (check_redundant_whitespace_alternation), with tests.