ruby-grape / grape / 36924858285

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Pull #3023

github

Raise from error! instead of throwing :error

error! threw :error, and a throw is not an exception. Active Record
commits a transaction that a throw leaves, so error! inside a
transaction saved what the block had written while the client was told
the request failed. A throw cannot leave the fiber it was thrown in
either, so error! inside an Async task answered 500.

error! now raises Grape::Exceptions::Halt, a StandardError carrying the
same ErrorResponse. The error middleware takes it inside its catch, so
it is rendered where a thrown error is and never reaches rescue_from.
Its backtrace is preset empty, as Validation's is, so raise skips
capturing one.

Raising costs more than throwing, so ErrorResponse is now a plain frozen
class rather than a Data. Every error response builds at least two of
them, and Data's constructor takes its keywords as a Hash it then
validates: about 450 ns each and 700 ns for the copy #with made, against
about 120 ns. It answers only what Grape reads off it, its readers, and
stays frozen; error_response builds its copy with new. Nothing compared,
hashed, converted or pattern-matched one, so the rest of Data's
interface is dropped, as UPGRADING says. Halt spells its keywords out
for the same reason. With both, an error! response is at least as fast
as before, and other error responses are faster.

throw :error from middleware and rescue_from handlers keeps working.

Fixes #2197

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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