ruby-grape / grape / 34322765255

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master: 99%

Pull #2919

github

Resolve a '%'-free path against a union without the encodings

Every route pattern is compiled with Mustermann's `uri_decode: true`, which
expands each literal character of a path into an alternation with its
percent-encodings -- `/resource7` becomes
`\/(?:r|%72)(?:e|%65)(?:s|%73)(?:o|%6F|%6f)...` -- so that `/a%2Eb` still
reaches a route declared as `/a.b`. The router's per-method union is the
disjunction of those patterns, so every request pays for the expansion: it
roughly doubles the compiled source, and it hides the literal prefix each
branch starts with, which is what would otherwise let Onigmo reject a
non-matching path without walking the alternatives. On a 500-route API,
failing to match cost 180us.

An input holding no '%' cannot take any of those alternatives, so for it the
union without them accepts exactly the same strings, by the same path through
the regexp, capturing the same substrings. `compile!` now derives that
stand-in per union and `transaction`, `#match?` and `#greedy_match?` read it
whenever the path has no '%'.

The stand-in is cut out of the union's source rather than recompiled from each
pattern with `uri_decode: false`. That is 20x cheaper -- one gsub and one
`Regexp.new` for the whole union against a fresh Mustermann parse per route --
and it is the more faithful transformation: `uri_decode: false` also drops the
`\+` branch that lets a plus match a literal space, which would make
`/with+space` (no '%' anywhere, so resolved here) miss a route the decode-aware
union matches.

Only alternations are rewritten, and only their `%XX` alternatives are dropped,
so a `requirements` Regexp inserted into the pattern verbatim survives whatever
it holds. Two shapes are stepped over rather than rewritten: a character class,
where `(?:` and `|` are literal characters and dropping them would shrink the
set a route matches, and an escape, so an escaped bracket cannot open a class.
The group itself is only unwrapped around a lone character ... (continued)

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