ruby-grape / grape / 24629950730 / 9

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master: 97%

Pull #2686

github

Precompute middleware content-type caches on the parent instance

Grape::Middleware::Base#call does dup.call!(env) per request, so the
+||=+ memoization on content_types / mime_types / content_types_indifferent_access
lived on the per-request dup — it was computed fresh every request.

This change:

- Adds a protected +precompute_content_types!+ helper on +Middleware::Base+
  that populates the three ivars on the parent instance at initialization
  time. Per-request dups then inherit the cached values via +dup+'s ivar
  copy instead of recomputing +with_indifferent_access+ (~1 µs each).
- Has +Middleware::Error+, +Middleware::Formatter+, and
  +Middleware::Versioner::Base+ call it from their +initialize+ (after
  +super+). Versioner::Base additionally warms +available_media_types+.
- Short-circuits +Middleware::Base#merge_headers+ when no headers were
  set, avoiding both the lazy +Grape::Util::Header.new+ allocation and
  an empty +merge!+ against the response.

No behavior change. Only middlewares that actually read content_types
opt into the warmup — plain +Middleware::Base+ subclasses still pay
nothing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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