ruby-grape / grape / 33958045014

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master: 99%

Pull #2901

github

Require a formatter in error_formatter and drop the unreachable 406 throw

`error_formatter :json` — with no formatter, positionally or as `with:` —
registered `nil`. `ErrorFormatter.formatter_for` returns a registered value
verbatim through its `key?` short-circuit, so that format resolved to no
formatter at all, and `Middleware::Error#format_message` fell through to a
`throw :error, 406`.

That throw could never deliver its 406: nothing catches `:error` around the
call. `#call!` has already left its `catch` by the time `error_response` runs,
and `run_rescue_handler` renders outside its own. So it raised
`UncaughtThrowError`, `render_response` rescued it, and the request answered
with the failsafe `500 Internal Server Error` in `text/plain` instead of the
status and message the API asked for.

Raise `ArgumentError` from the DSL when no formatter is given, so the mistake
surfaces where it is made, and drop the dead branch — `formatter_for` always
resolves to a registered formatter, `default_error_formatter` or
`ErrorFormatter::Txt`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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