Merge pull request #23120 from vipulnsward/always-set-vary-for-static-assets

Its ideal to set Vary: Accept-Encoding, irrespective of whether gzipped or not

actionpack/lib/action_dispatch/middleware/static.rb

@@ -65,7 +65,7 @@ def serve(request)
         status, headers, body = @file_server.call(request.env)
       end
 
-      headers['Vary'] = 'Accept-Encoding' if gzip_path
+      headers['Vary'] = 'Accept-Encoding'
 
       return [status, headers, body]
     ensure

actionpack/test/dispatch/static_test.rb

@@ -233,7 +233,7 @@ def assert_gzip(file_name, response)
     def assert_html(body, response)
       assert_equal body, response.body
       assert_equal "text/html", response.headers["Content-Type"]
-      assert_nil response.headers["Vary"]
+      assert_not_nil response.headers["Vary"]
     end
 
     def get(path, headers = {})