At the very least this needs tests and a CHANGELOG entry.

This has been discussed before though and the consensus was that a redirect should not set a content type because there's no content. If you find an RFC that says otherwise happy to consider. I'll leave this open for now.

Well, redirects are unusable for me with content_type :xml, content_type :json as well as default_format :json in my base API class. As I said, the formatters try to interpret the empty body as JSON or XML and fail.

If you give me the go-ahead, I'll gladly add a test.

I am just confused to why they are not usable given that it's the "correct" behavior?

When I redirect, I obviously don't want to render any JSON or XML, so the formatters shouldn't even try.

Maybe I am missing the point, can you explain "which confused the XML and JSON helpers" please? I am not trying to be difficult, just trying to help :)

Here you go:

get 'me' do
  redirect "users/#{current_user.id}"
end

With default_format set to XML, I get this output:

<error>
  <message>cannot convert String to xml</message>
</error>

For JSON, it works now. Weird.

Ok this is what I'd expect. I think we need defined behavior for XML here, which is not an error. It's the same problem as discussed in #1159, can we merge these two discussions?

I am going to close this in favor of #1162, without merging. Lets discuss what the "right fix" would be.