Incompatibility with Rack 2.1.0 and higher

[ignatbagaev]

Hi!
I use Grape in my application and after updating Rack to 2.1.1, I get an error
NoMethodError - undefined method '[]' for nil:NilClass without any backtrace. During debugging I found that it was raising in Grape::Router#cascade?

def cascade?(response)
  response && response[1][Grape::Http::Headers::X_CASCADE] == 'pass'
end

and the response looks like

[#<Rack::Response:0x00007fc561a338c8 @status=200, @header={"Content-Type"=>"application/json"}, @writer=#<Method: Rack::Response(Rack::Response::Helpers)#append>, @block=nil, @length=0, @body=["{\"foo\":\"bar\"}"], @buffered=false>, nil, nil]

I made some investigation and found that Rack team removed #to_ary from Rack::Response in version 2.1.0 and this change made the result of Grape::MIddleware::Formatter#build_formatted_response not implicitly convertable to Array. This is why I had response like a mentioned above instead of response like

[response_status, response_headers, response_body]

To fix this behavior just #finish an instance of Rack::Response in Formatter middleware:
change

Rack::Response.new(bodymap, status, headers)

at https://github.com/ruby-grape/grape/blob/master/lib/grape/middleware/formatter.rb#L49 to

Rack::Response.new(bodymap, status, headers).finish

[dnesteryuk]

@ignatbagaev Did you try Grape 1.3.0? There was a fix made by @ioquatix

[ignatbagaev]

@dnesteryuk thanks for the quick response! I appreciate it!
No, I did not because Grape 1.3.0 has a dry-types >= 1.1.0 dependency which is currently incompatible with my app.
I can not see any changes by @ioquatix in changelog, so I do not really understand which fix you meant. Can you please provide a link to PR? But as I can see it in master branch the "broken" code is still there (instance of Rack::Response not finished in the Formatter middleware).

UPDATE: I use Grape 1.2.5 and Rack 2.1.1

[ignatbagaev]

@dnesteryuk already found this PR and rechecked the master. Looks like 1.3.0 really fixes this issue.

I close the issue and related PR

Thank you!