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. https://github.com/rack/rack/pull/1887

actionpack/lib/action_dispatch/journey/router.rb

@@ -47,7 +47,7 @@ module ActionDispatch
 
           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 @@ module ActionDispatch
             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 @@ module ActionDispatch
     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 @@ module ActionDispatch
         end
       end
 
-      [status, headers, body]
+      response
     end
   end
 end

railties/lib/rails/rack/logger.rb

@@ -34,9 +34,15 @@ module Rails
           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