Format from Accept headers have higher precedence than path extension format

actionpack/lib/action_dispatch/http/mime_negotiation.rb

@@ -67,10 +67,10 @@ module ActionDispatch
 
           v = if params_readable
             Array(Mime[parameters[:format]])
-          elsif extension_format = format_from_path_extension
-            [extension_format]
           elsif use_accept_header && valid_accept_header
             accepts
+          elsif extension_format = format_from_path_extension
+            [extension_format]
           elsif xhr?
             [Mime[:js]]
           else

actionpack/test/dispatch/request_test.rb

@@ -909,6 +909,15 @@ class RequestFormat < BaseRequestTest
       assert_equal [Mime[:html]], request.formats
     end
   end
+
+  test "formats from accept headers have higher precedence than path extension" do
+    request = stub_request 'HTTP_ACCEPT' => 'application/json',
+                           'PATH_INFO' => '/foo.xml'
+
+    assert_called(request, :parameters, times: 1, returns: {}) do
+      assert_equal [Mime[:json]], request.formats
+    end
+  end
 end
 
 class RequestMimeType < BaseRequestTest