README.md and docs/API.md both previously documented "no way to list
every name a pattern defines without already knowing what to look
for" as an accepted limitation of Pattern_groupindex_lookup being the
only access to groupindex. It was not actually a hard constraint: the
underlying GroupIndex struct (regexx.c) already stores every name and
its group number in two parallel arrays, populated once at compile
time; only a public accessor was missing.
Pattern_groupindex_count returns the number of named groups;
Pattern_groupindex_at(self, i, &name) for 0 <= i < count writes the
i-th name and returns its 1-based group number, or returns -1 for an
out-of-range i. Enumeration order is declaration order, verified
against a real CPython 3.11 interpreter to match groupindex's own
practical (insertion-order) iteration order, not just assumed.
Verified directly (count/name/group-number correctness, matching the
exact snippet now in USAGE.md's own output), full 3,252-case suite
unaffected (3252/3252, this is a pure accessor addition touching no
matching logic), clean AddressSanitizer/UndefinedBehaviorSanitizer.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EjuMk8kY9SDus1wWe2K9xY
retoorandClaude Sonnet 5
09718eaaf6