Render a redirect message as the plain text it claims to be

[ericproulx]

Summary

#redirect announces its message as text/plain — and has since it was introduced in 2015, in a commit literally titled "Redirect as plain text with optional message override" — but it only ever set the header. The body was still handed to the API's own formatter:

class API < Grape::API
  format :json
  get('/r') { redirect '/there' }
end

HTTP/1.1 302 Found
Location: /there
Content-Type: text/plain

"This resource has been moved temporarily to /there."

Quotes included. That is neither valid plain text nor what a client reading the content type would expect, and the header and body contradict each other.

API format	before	after
format :json	text/plain + "…moved temporarily to /there." (quoted)	text/plain + …moved temporarily to /there.
format :txt	correct already	unchanged
format :xml	quoted/encoded by the XML formatter	plain text

The existing #redirect specs missed it because they run on the default :txt format, where the formatter is a no-op.

Approach

Set api.format alongside the header — the same lever an endpoint already has via #api_format (spec'd at api_spec.rb:4494) — so the message is rendered by the txt formatter whatever the API declares. :txt is always resolvable: Grape::Formatter.formatter_for falls back to the built-in registry, which is not narrowed by the API's format.

It is per-request rack env, so other routes on the same API are unaffected — there is a spec pinning that.

Backward compatibility

No UPGRADING entry. The Content-Type was already text/plain; only the body changes, and only for APIs whose format is not :txt — from an encoded form that contradicted the header to the plain text it always claimed to be. Redirect bodies are informational; clients follow Location.

Longstanding rather than a regression: present since v0.14.0 (d1bba79d, 2015) and identical in 3.3.4.

Test plan

• 3 new examples in endpoint_spec.rb under #redirect: plain-text body on a JSON API, an overridden body likewise, and a guard that other routes keep the API's format. Verified 2 of them fail without the lib/ change.
• Full RSpec suite passes locally (2546 examples, 0 failures).
• RuboCop clean.
• CI green.

🤖 Generated with Claude Code

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