Remove Content-Length header from :no_content responses

actionpack/lib/action_controller/response.rb

@@ -231,10 +231,13 @@ def convert_content_type!
       # Don't set the Content-Length for block-based bodies as that would mean
       # reading it all into memory. Not nice for, say, a 2GB streaming file.
       def set_content_length!
-        unless body.respond_to?(:call) || (status && status.to_s[0..2] == '304')
-          self.headers["Content-Length"] ||= body.size
+        if status && status.to_s[0..2] == '204'
+          headers.delete('Content-Length')
+        elsif length = headers['Content-Length']
+          headers['Content-Length'] = length.to_s
+        elsif !body.respond_to?(:call) && (!status || status.to_s[0..2] != '304')
+          headers["Content-Length"] = body.size.to_s
         end
-        headers["Content-Length"] = headers["Content-Length"].to_s if headers["Content-Length"]
       end
 
       def convert_language!

actionpack/test/controller/render_test.rb

@@ -1218,6 +1218,11 @@ def test_head_with_symbolic_status
     assert_equal "404 Not Found", @response.status
     assert_response :not_found
 
+    get :head_with_symbolic_status, :status => "no_content"
+    assert_equal "204 No Content", @response.status
+    assert !@response.headers.include?('Content-Length')
+    assert_response :no_content
+
     ActionController::StatusCodes::SYMBOL_TO_STATUS_CODE.each do |status, code|
       get :head_with_symbolic_status, :status => status.to_s
       assert_equal code, @response.response_code
@@ -1470,7 +1475,7 @@ def test_render_against_etag_request_should_304_when_match
   def test_render_against_etag_request_should_have_no_content_length_when_match
     @request.if_none_match = etag_for("hello david")
     get :render_hello_world_from_variable
-    assert !@response.headers.has_key?("Content-Length")
+    assert !@response.headers.has_key?("Content-Length"), @response.headers['Content-Length']
   end
 
   def test_render_against_etag_request_should_200_when_no_match