only call self.content_type= when there is a response

Apparently the AbstractController (whatever "abstract" means) is
expected to work without a request and response.

2 files changed, 6 insertions, 3 deletions

diff --git a/actionpack/lib/action_controller/metal/mime_responds.rb b/actionpack/lib/action_controller/metal/mime_responds.rb
index 1db68db20f..e62da0fa70 100644
--- a/actionpack/lib/action_controller/metal/mime_responds.rb
+++ b/actionpack/lib/action_controller/metal/mime_responds.rb
@@ -191,6 +191,7 @@ module ActionController #:nodoc:
 
       if format = collector.negotiate_format(request)
         _process_format(format)
+        _set_content_type _get_content_type format
         response = collector.response
         response ? response.call : render({})
       else
diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index a2d671486d..c8934b367f 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -56,10 +56,12 @@ module ActionController
       nil
     end
 
-    def _process_format(format)
-      super
+    def _get_content_type(rendered_format)
+      self.content_type || super
+    end
 
-      self.content_type ||= format.to_s
+    def _set_content_type(format)
+      self.content_type = format
     end
 
     # Normalize arguments by catching blocks and setting them on :update.