1 files changed, 13 insertions, 0 deletions
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index 555bc9dbc8..f8a33ffe24 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -140,6 +140,19 @@ module Rails
       end
     end
 
+    def app
+      raise "You can't use Engine as rack application without providing valid rack endpoint" unless endpoint
+      @app ||= config.middleware.build(endpoint)
+    end
+
+    def endpoint
+      self.class.endpoint
+    end
+
+    def call(env)
+      app.call(env)
+    end
+
     # Add configured load paths to ruby load paths and remove duplicates.
     initializer :set_load_path, :before => :bootstrap_hook do
       _all_load_paths.reverse_each do |path|