Add internal middleware stack to Dispatcher

  config.middleware.use Rack::Cache

actionpack/lib/action_controller.rb

@@ -57,6 +57,7 @@ def self.load_all!
   autoload :Integration, 'action_controller/integration'
   autoload :IntegrationTest, 'action_controller/integration'
   autoload :Layout, 'action_controller/layout'
+  autoload :MiddlewareStack, 'action_controller/middleware_stack'
   autoload :MimeResponds, 'action_controller/mime_responds'
   autoload :PolymorphicRoutes, 'action_controller/polymorphic_routes'
   autoload :RackRequest, 'action_controller/rack_process'

actionpack/lib/action_controller/dispatcher.rb

@@ -85,6 +85,9 @@ def failsafe_logger
         end
     end
 
+    cattr_accessor :middleware
+    self.middleware = MiddlewareStack.new
+
     cattr_accessor :error_file_path
     self.error_file_path = Rails.public_path if defined?(Rails.public_path)
 
@@ -93,6 +96,7 @@ def failsafe_logger
 
     def initialize(output = $stdout, request = nil, response = nil)
       @output, @request, @response = output, request, response
+      @app = @@middleware.build(lambda { |env| self._call(env) })
     end
 
     def dispatch_unlocked
@@ -127,6 +131,10 @@ def dispatch_cgi(cgi, session_options)
     end
 
     def call(env)
+      @app.call(env)
+    end
+
+    def _call(env)
       @request = RackRequest.new(env)
       @response = RackResponse.new(@request)
       dispatch

actionpack/lib/action_controller/middleware_stack.rb

@@ -0,0 +1,42 @@
+module ActionController
+  class MiddlewareStack < Array
+    class Middleware
+      attr_reader :klass, :args, :block
+
+      def initialize(klass, *args, &block)
+        @klass = klass.is_a?(Class) ? klass : klass.to_s.constantize
+        @args = args
+        @block = block
+      end
+
+      def ==(middleware)
+        case middleware
+        when Middleware
+          klass == middleware.klass
+        when Class
+          klass == middleware
+        else
+          klass == middleware.to_s.constantize
+        end
+      end
+
+      def inspect
+        str = @klass.to_s
+        @args.each { |arg| str += ", #{arg.inspect}" }
+        str
+      end
+
+      def build(app)
+        klass.new(app, *args, &block)
+      end
+    end
+
+    def use(*args, &block)
+      push(Middleware.new(*args, &block))
+    end
+
+    def build(app)
+      reverse.inject(app) { |a, e| e.build(a) }
+    end
+  end
+end

railties/lib/initializer.rb

@@ -881,6 +881,11 @@ def to_prepare(&callback)
       end
     end
 
+    def middleware
+      require 'action_controller'
+      ActionController::Dispatcher.middleware
+    end
+
     def builtin_directories
       # Include builtins only in the development environment.
       (environment == 'development') ? Dir["#{RAILTIES_PATH}/builtin/*/"] : []

railties/lib/tasks/middleware.rake

@@ -0,0 +1,7 @@
+desc 'Prints out your Rack middleware stack'
+task :middleware => :environment do
+  ActionController::Dispatcher.middleware.each do |middleware|
+    puts "use #{middleware.inspect}"
+  end
+  puts "run ActionController::Dispatcher.new"
+end