Max Hsu 340d4b033e fix(swift): remove catastrophic backtracking in Vapor route regex (#1547) ...

The arg-list group `(?:[^,()]+,\s*)*` was ambiguous: the trailing `\s*`
and the next iteration's `[^,()]+` could both claim the same run of
spaces, so a `.METHOD(...)` call with many comma-separated args that
never reaches `use:` forced an exponential search. Measured on
`app.get(arg0: value0, ...)`: 40ms at 20 args, 647ms at 24, 41.7s at 30,
and no result after 120s at 60.

Anchoring each repetition at a comma (`(?:[^,()]+,)*\s*`) makes the split
unique — `,` is outside the char class, so there is nothing to
re-partition. Same input is now 0.09ms at 1000 args.

Match behaviour is unchanged: all four capture groups are identical on 18
hand-written Vapor route shapes (no args, single/multi path segments,
`X.parameter`, multi-line calls, Environment.get non-matches) and on
200k fuzzed inputs.

Fixes #1544

2026-08-22 11:53:26 -05:00

62 KiB

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