default_headers plugin silently fails w/ capitalized Content-Type header on Rack 3

[benalavi]

Ran into this when upgrading to Rack 3. The below app will silently ignore the Content-Type header (it returns content-type: text/html rather than content-type: application/json), but lowercase other arbitrary capitalized headers.

require "roda"

class API < Roda
  plugin :default_headers,
    "Content-Type" => "application/json",
    "Foo" => "bar"

  route do |r|
    r.get "" do
      "Hello"
    end
  end
end

run API.freeze

< HTTP/1.1 200 OK
< content-type: text/html
< foo: bar
< Content-Length: 5

I assume this is related to the Rack 3 change that all headers must be lowercase. So maybe w/ Rack 3 this is now expected behavior, in which case it might just warrant a tiny change to the documentation: https://github.com/jeremyevans/roda/blob/master/lib/roda/plugins/default_headers.rb#L16 -- but it was surprising that it worked for the "Foo" header.

Rack 3 seems to raise now if you try to assign a non-lowercase header, which was helpful for us when upgrading.

Lowercase content-type works as expected:

require "roda"

class API < Roda
  plugin :default_headers,
    "content-type" => "application/json",
    "Foo" => "bar"

  route do |r|
    r.get "" do
      "Hello"
    end
  end
end

run API.freeze

< HTTP/1.1 200 OK
< content-type: application/json
< foo: bar
< Content-Length: 5

[jeremyevans]

Thank you very much for the report. This is because Roda::RodaResponse::DEFAULT_HEADERS is not a Rack::Headers instance by default. I'll fix that shortly.

[jeremyevans]

Fixed in 8757ac7

[benalavi]

Thanks! That fixed our broken case as well 👍