Dont stream back cookie value if it was set to the same value

actionpack/lib/action_dispatch/middleware/cookies.rb

@@ -170,12 +170,14 @@ def []=(key, options)
           options = { :value => value }
         end
 
-        @cookies[key.to_s] = value
-
         handle_options(options)
 
-        @set_cookies[key.to_s] = options
-        @delete_cookies.delete(key.to_s)
+        if @cookies[key.to_s] != value or options[:expires]
+          @cookies[key.to_s] = value
+          @set_cookies[key.to_s] = options
+          @delete_cookies.delete(key.to_s)
+        end
+
         value
       end
 

actionpack/test/dispatch/cookies_test.rb

@@ -179,6 +179,18 @@ def test_setting_cookie
     assert_equal({"user_name" => "david"}, @response.cookies)
   end
 
+  def test_setting_the_same_value_to_cookie
+    request.cookies[:user_name] = 'david'
+    get :authenticate
+    assert response.cookies.empty?
+  end
+
+  def test_setting_the_same_value_to_permanent_cookie
+    request.cookies[:user_name] = 'Jamie'
+    get :set_permanent_cookie
+    assert response.cookies, 'user_name' => 'Jamie'
+  end
+
   def test_setting_with_escapable_characters
     get :set_with_with_escapable_characters
     assert_cookie_header "that+%26+guy=foo+%26+bar+%3D%3E+baz; path=/"
@@ -564,4 +576,4 @@ def assert_not_cookie_header(expected)
         assert_not_equal expected.split("\n"), header
       end
     end
-end
+end