only construct one request in an engine

railties/lib/rails/application.rb

@@ -156,15 +156,6 @@ def run_load_hooks! # :nodoc:
       self
     end
 
-    # Implements call according to the Rack API. It simply
-    # dispatches the request to the underlying middleware stack.
-    def call(env)
-      req = ActionDispatch::Request.new env
-      env["ORIGINAL_FULLPATH"] = req.fullpath
-      env["ORIGINAL_SCRIPT_NAME"] = req.script_name
-      super(env)
-    end
-
     # Reload application routes regardless if they changed or not.
     def reload_routes!
       routes_reloader.reload!
@@ -517,6 +508,13 @@ def validate_secret_key_config! #:nodoc:
 
     private
 
+    def build_request(env)
+      req = super
+      env["ORIGINAL_FULLPATH"] = req.fullpath
+      env["ORIGINAL_SCRIPT_NAME"] = req.script_name
+      req
+    end
+
     def build_middleware
       config.app_middleware + super
     end

railties/lib/rails/engine.rb

@@ -523,11 +523,8 @@ def endpoint
 
     # Define the Rack API for this engine.
     def call(env)
-      env.merge!(env_config)
-      req = ActionDispatch::Request.new env
-      req.routes = routes
-      req.engine_script_name = req.script_name
-      app.call(env)
+      req = build_request env
+      app.call req.env
     end
 
     # Defines additional Rack env configuration that is added on each call.
@@ -697,6 +694,14 @@ def _all_load_paths #:nodoc:
 
     private
 
+    def build_request(env)
+      env.merge!(env_config)
+      req = ActionDispatch::Request.new env
+      req.routes = routes
+      req.engine_script_name = req.script_name
+      req
+    end
+
     def build_middleware
       config.middleware
     end