Merge pull request #16793 from javan/comply_with_rack_content_length_middleware

Add support for Rack::ContentLength middelware

actionpack/lib/action_dispatch/http/response.rb

@@ -380,6 +380,10 @@ def respond_to?(method, include_private = false)
       def to_path
         @response.stream.to_path
       end
+
+      def to_ary
+        nil
+      end
     end
 
     def rack_response(status, header)

actionpack/test/dispatch/response_test.rb

 require 'abstract_unit'
+require 'timeout'
+require 'rack/content_length'
 
 class ResponseTest < ActiveSupport::TestCase
   def setup
@@ -238,6 +240,18 @@ def test_response_body_encoding
     end
   end
 
+  test "compatibility with Rack::ContentLength" do
+    @response.body = 'Hello'
+    app = lambda { |env| @response.to_a }
+    env = Rack::MockRequest.env_for("/")
+
+    status, headers, body = app.call(env)
+    assert_nil headers['Content-Length']
+
+    status, headers, body = Rack::ContentLength.new(app).call(env)
+    assert_equal '5', headers['Content-Length']
+  end
+
   test "implicit destructuring and Array conversion is deprecated" do
     response = ActionDispatch::Response.new(404, { 'Content-Type' => 'text/plain' }, ['Not Found'])