Look for a 405 neighbour only on paths the method has no route on

[ericproulx]

When the routes for a request's method all miss its path, #neighbours walks @union — one greedy route per path — for a route to answer 405 with. A 404 therefore walks two unions: its method's, then every path.

Most of that second walk cannot succeed. collect_route_config_per_pattern groups routes by pattern_regexp and hands each group's greedy route the pattern those routes share. So once the union for a method has missed a path, the greedy route of every path that method has a route on has missed it too.

compile! now works out, per method, the greedy routes of the paths it has no route on, and compiles those into a union of their own; after a miss, only that one is walked. In an API where every path answers GET, a GET leaves nothing to walk.

Behaviour is unchanged

• The subset is built from the same members as @union, in the same order, so a path resolves to the same greedy route either way — same 405, same Allow header.
• A method with no routes of its own covers no path and still walks all of @union. That is also what auto-OPTIONS does, unless OPTIONS routes are declared.
• Methods that leave the same paths uncovered (PUT and DELETE on a member, say) share one union.
• Once a route has matched and cascaded, the neighbour is never read, so it is no longer looked up.

A subset of @union numbers its groups differently from @union itself, so each neighbour union carries the group of each of its routes rather than reading regexp_capture_group.

Measured

Ruby 4.0.6 without YJIT, median of 5 interleaved rounds against an extract of master. The API is CRUD-shaped: GET and POST on each collection, GET, PUT and DELETE on each member, prefix + path version + format :json.

	10 resources	100 resources	250 resources
GET 404	+74.6%	+97.9%	+93.5%
POST 404	+24.3%	+40.4%	+31.3%
POST 405	+5.8%	+27.7%	+21.3%
GET, middle route (control)	+4.8%	−2.0%	−0.7%
OPTIONS (control)	−0.8%	+0.5%	−4.7%

POST gains less because it has no route on the member paths, which therefore stay candidates. Boot, full API instance build: +5.1%, +8.5%, +5.8%, and +0.9% at 500 resources.

The resource names are varied on purpose. Routes that share one literal (resource1, resource2, …) let Onigmo reject a path lacking it by substring search without walking the union at all, which inflates every miss measurement and is not something a real API gets.

🤖 Generated with Claude Code

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