[ericproulx]

Stacked on #3043, so this diff shows only the refactor. It will be rebased onto master once #3043 merges.

Summary

No behaviour change.

#settle and #neighbours handled two situations, no route matching and a route declining, and told them apart with a cascaded flag that was true exactly when a route had matched. That flag becomes two paths:

def settle(input, method, env, response, exact_route)
  return after_miss(input, method, env) unless response

  final_response(response) || after_cascade(input, method, env, exact_route)
end

• #after_miss tries the allowed methods (OPTIONS first), the ANY routes, then the 405.
• #after_cascade tries the siblings, then the ANY routes, and never looks for allowed methods.

#halt?, a predicate that closed a body as a side effect, is gone. The two lookups that repeated routes.detect now go through #matched_route.

Renames

Before	After	Why
transaction, bucket_transaction, union_transaction	dispatch, dispatch_to_bucket, dispatch_to_union	Nothing atomic or rolled back here
match?(input, '*')	star_route_for(input)	Returns a route, and '*' was its only argument
greedy_match?	allowed_methods_route_for	Returns a route
neighbour_match?	neighbour_route_for	Returns a route
last_neighbor_route	allowed_methods_route	"Last" was stale, and the spelling differed from neighbour
Router::GreedyRoute	Router::AllowedMethodsRoute	It matches on the path whatever the method, and only ever answers with the methods the path allows

Router::GreedyRoute is the only name that isn't private, and it's undocumented and never handed to users. GitHub code search finds it only in this repo across the ruby-grape org, grape-swagger included, so there's no alias and no UPGRADING entry. @neutral_map and @neighbour_map keep their names.

Measured

Against #3043, one worktree, order alternated each round, 100 CRUD resources plus two header versions.

Scenario	Calls per request	Allocations
GET static	182 → 181	10 → 10
GET with a param	223 → 222	15 → 15
GET 404	60 → 57	4 → 4
POST 405	407 → 404	30 → 30
OPTIONS	445 → 443	13 → 13
GET v2, declined by v1	3185 → 3181	429 → 429

Throughput is flat. A first 7-round run read −3.9% on POST 405 without JIT and −3.8% on GET with a param under YJIT, so those two were rerun for 9 rounds with an A/A control:

Mode	Scenario	Head vs base	A/A
No JIT	GET with a param	+0.2% (5/9)	−0.3% (4/9)
No JIT	POST 405	+0.4% (6/9)	−0.4% (3/9)
YJIT	GET with a param	−0.2% (4/9)	−1.0% (4/9)
YJIT	POST 405	+1.8% (8/9)	+1.1% (5/9)

Test plan

• Same answer as Answer 404 when every route on a path cascades #3043 for 7,296 requests: 8 methods × 19 paths × 6 Accept headers × 8 APIs, covering REST, catch-all ANY, cascading versions, a last version with cascade: false, no auto-OPTIONS/HEAD, buckets and mounted Rack apps. Status, Allow, X-Cascade, content type and first body line are compared, plus recognize_path.
• bundle exec rake: RuboCop clean, 3167 examples, 0 failures.
• CI green.

🤖 Generated with Claude Code

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