Support POSIX bracket classes in regex char classes#1552
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This pull request implements support for POSIX bracket classes (e.g., [:alpha:], [:digit:]) within character classes in the regex engine, accompanied by new test cases. The review feedback identifies two key improvements: raising a compile error for invalid POSIX class names instead of falling back to literal parsing to avoid silent failures, and adding support for the [:ascii:] class to improve compatibility with Ruby's regex engine.
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Recognize [:name:] POSIX classes inside bracket expressions and expand
them to their ASCII ranges via the existing class-add helpers. Supports
alpha, digit, alnum, space, upper, lower, punct, blank, cntrl, xdigit,
print, graph, word, and ascii. The in-class negated form [:^name:] adds
the ASCII complement plus utf8_any, mirroring the \D/\W/\S shorthands.
Enclosing negation ([^[:alpha:]]) is applied by the existing RE_NCLASS
emit. An unrecognized POSIX class name raises a RegexpError ("invalid
POSIX bracket type"), matching CRuby, instead of silently matching
nothing. Previously [:alpha:] was parsed as the literal set {:,a,l,p,h,t},
so the class never matched alphabetic input.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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POSIX bracket classes inside a character class —
[[:alpha:]],[[:digit:]], and the rest of the family — previously matched nothing. The bracket reader had no recognition of the[:name:]syntax, so[:alpha:]was parsed as a char class containing the literal characters:,a,l,p,h,t, which never matches alphabetic input.The bracket-class reader in
lib/regexp/re_compile.cnow recognizes[:…:]and expands the named class to its ASCII ranges using the same range/bit helpers that back\dand\w(no parallel mechanism). Supported names:alpha, digit, alnum, space, upper, lower, punct, blank, cntrl, xdigit, print, graph, word. Enclosing negation such as[^[:alpha:]]is handled by the existingRE_NCLASSemit, identical to how the engine already negates classes. ASCII semantics, matching CRuby for ASCII input; all 13 names were verified byte-for-byte against ruby. Unicode\p{L}properties remain out of scope.A new
test/regex_posix_class.rb(.expectedregenerated from ruby) covers alpha/digit/alnum/space/upper/lower, a negated class, combined literal+POSIX brackets, bothscanand a plainmatch, and a non-constant subject routed through a method parameter so the runtime engine is exercised rather than constant-folded. The full suite is green under-Werror.Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com