Don't add content-length header.

[ioquatix]

@last_response.finish modifies the response, and in Rack 3.1 it can add content-length which in some cases is unexpected.

Rails is trying to test “streaming” - #each without #to_ary - and it’s tricky.

      def process_request(uri, env)
        env['HTTP_COOKIE'] ||= cookie_jar.for(uri)
        @last_request = Rack::Request.new(env)
        status, headers, body = @app.call(env).to_a

        @last_response = MockResponse.new(status, headers, body, env['rack.errors'].flush)
        close_body(body)
        cookie_jar.merge(last_response.headers['set-cookie'], uri)
        @after_request.each(&:call)
        @last_response.finish. # <-------------------- Adds 'content-length' header

        yield @last_response if block_given?

        @last_response
      end

The above code comes from Rack::Test::Session. The problem is, it adds content-length header which was not present in the original response. It’s reasonable to do that if you are dealing with an actual response… But rails is interested in what was returned by the application - not some normalised “response”.

Maybe the change to Rack::Response#finish was problematic: rack/rack#2149

test.rb:

#!/usr/bin/env ruby

$LOAD_PATH.unshift File.expand_path('lib', __dir__)
require 'rack'

response = Rack::MockResponse.new(200, {}, 'Hello, World!')

pp response
response.finish
pp response

3-0-stable:

#<Rack::MockResponse:0x000000011bc7af08
 @block=nil,
 @body=["Hello, World!"],
 @buffered=true,
 @cookies={},
 @errors="",
 @headers={},
 @length=13,
 @original_headers={},
 @status=200,
 @writer=#<Method: Rack::MockResponse(Rack::Response::Helpers)#append(chunk) /Users/samuel/Developer/rack/rack/lib/rack/response.rb:353>>
#<Rack::MockResponse:0x000000011bc7af08
 @block=nil,
 @body=["Hello, World!"],
 @buffered=true,
 @cookies={},
 @errors="",
 @headers={},
 @length=13,
 @original_headers={},
 @status=200,
 @writer=#<Method: Rack::MockResponse(Rack::Response::Helpers)#append(chunk) /Users/samuel/Developer/rack/rack/lib/rack/response.rb:353>>

3-1-stable:

#<Rack::MockResponse:0x000000011dab97f8
 @block=nil,
 @body=["Hello, World!"],
 @buffered=true,
 @cookies={},
 @errors="",
 @headers={},
 @length=13,
 @original_headers={},
 @status=200,
 @writer=#<Method: Rack::MockResponse(Rack::Response::Helpers)#append(chunk) /Users/samuel/Developer/rack/rack/lib/rack/response.rb:353>>
#<Rack::MockResponse:0x000000011dab97f8
 @block=nil,
 @body=["Hello, World!"],
 @buffered=true,
 @cookies={},
 @errors="",
 @headers={"content-length"=>"13"},
 @length=13,
 @original_headers={},
 @status=200,
 @writer=#<Method: Rack::MockResponse(Rack::Response::Helpers)#append(chunk) /Users/samuel/Developer/rack/rack/lib/rack/response.rb:353>>

I actually don’t think the latter behaviour is bad - if we know the content-length we can add it… and we do in that case. So, maybe rack-test should not invoke #finish?

[ioquatix]

It's interesting to see a lot of tests fail. Rack::Response can add content-length if you write to it... I wonder if that's what's happening here.