Reuse the Array object passed from parent middleware

This patch reduces Array object allocations from some Rack middleware per each
request by reusing the Array object that wraps status, headers, and body
objects. This is a Rails version of the same improvements that has already been
pushed to Rack 3.0. rack/rack#1887

Author: amatsuda

actionpack/lib/action_dispatch/journey/router.rb

@@ -47,7 +47,7 @@ def serve(req)
 
           req.path_parameters = tmp_params
 
-          status, headers, body = route.app.serve(req)
+          _, headers, _ = response = route.app.serve(req)
 
           if "pass" == headers["X-Cascade"]
             req.script_name     = script_name
@@ -56,7 +56,7 @@ def serve(req)
             next
           end
 
-          return [status, headers, body]
+          return response
         end
 
         [404, { "X-Cascade" => "pass" }, ["Not Found"]]

actionpack/lib/action_dispatch/middleware/cookies.rb

@@ -699,7 +699,7 @@ def initialize(app)
     def call(env)
       request = ActionDispatch::Request.new env
 
-      status, headers, body = @app.call(env)
+      _, headers, _ = response = @app.call(env)
 
       if request.have_cookie_jar?
         cookie_jar = request.cookie_jar
@@ -711,7 +711,7 @@ def call(env)
         end
       end
 
-      [status, headers, body]
+      response
     end
   end
 end

railties/lib/rails/rack/logger.rb

@@ -34,9 +34,15 @@ def call_app(request, env) # :doc:
           handle.start
 
           logger.info { started_request_message(request) }
-          status, headers, body = @app.call(env)
+          status, headers, body = response = @app.call(env)
           body = ::Rack::BodyProxy.new(body, &handle.method(:finish))
-          [status, headers, body]
+
+          if response.frozen?
+            [status, headers, body]
+          else
+            response[2] = body
+            response
+          end
         rescue Exception
           handle.finish
           raise