Cleanup junk metal and revise API

API Change: Returning a "X-Cascade: pass" header triggers the cascade
instead of a 404 response.

actionpack/lib/action_controller/railtie.rb

@@ -37,11 +37,33 @@ module ActionController
       ActionController::Base.view_paths = view_path if ActionController::Base.view_paths.blank?
     end
 
-    initializer "action_controller.initialize_metal" do |app|
-      Rails::Rack::Metal.requested_metals = app.config.metals
+    class MetalMiddlewareBuilder
+      def initialize(metals)
+        @metals = metals
+      end
 
-      app.config.middleware.insert_before(:"ActionDispatch::ParamsParser",
-        Rails::Rack::Metal, :if => Rails::Rack::Metal.metals.any?)
+      def new(app)
+        ActionDispatch::Cascade.new(@metals, app)
+      end
+
+      def name
+        ActionDispatch::Cascade.name
+      end
+      alias_method :to_s, :name
+    end
+
+    initializer "action_controller.initialize_metal" do |app|
+      metal_root = "#{Rails.root}/app/metal"
+      load_list = app.config.metals || Dir["#{metal_root}/**/*.rb"]
+
+      metals = load_list.map { |metal|
+        metal = File.basename(metal.gsub("#{metal_root}/", ''), '.rb')
+        require_dependency metal
+        metal.camelize.constantize
+      }.compact
+
+      middleware = MetalMiddlewareBuilder.new(metals)
+      app.config.middleware.insert_before(:"ActionDispatch::ParamsParser", middleware)
     end
 
     # # Prepare dispatcher callbacks and run 'prepare' callbacks

railties/lib/rails/rack.rb

@@ -2,7 +2,6 @@ module Rails
   module Rack
     autoload :Debugger, "rails/rack/debugger"
     autoload :LogTailer, "rails/rack/log_tailer"
-    autoload :Metal, "rails/rack/metal"
     autoload :Static, "rails/rack/static"
   end
 end

railties/lib/rails/rack/metal.rb

@@ -1,59 +0,0 @@
-require 'active_support/ordered_hash'
-require 'active_support/core_ext/class/attribute_accessors'
-require 'active_support/dependencies'
-
-module Rails
-  module Rack
-    class Metal
-      NotFoundResponse = [404, {}, []].freeze
-      NotFound = lambda { NotFoundResponse }
-
-      cattr_accessor :metal_paths
-      self.metal_paths = ["#{Rails.root}/app/metal"]
-      cattr_accessor :requested_metals
-      
-      cattr_accessor :pass_through_on
-      self.pass_through_on = 404
-
-      def self.metals
-        matcher = /#{Regexp.escape('/app/metal/')}(.*)\.rb\Z/
-        metal_glob = metal_paths.map{ |base| "#{base}/**/*.rb" }
-        all_metals = {}
-
-        metal_glob.each do |glob|
-          Dir[glob].sort.map do |file|
-            file = file.match(matcher)[1]
-            all_metals[file.camelize] = file
-          end
-        end
-
-        load_list = requested_metals || all_metals.keys
-
-        load_list.map do |requested_metal|
-          if metal = all_metals[requested_metal]
-            require_dependency metal
-            requested_metal.constantize
-          end
-        end.compact
-      end
-
-      def initialize(app)
-        @app = app
-        @pass_through_on = {}
-        [*self.class.pass_through_on].each { |status| @pass_through_on[status] = true }
-        
-        @metals = ActiveSupport::OrderedHash.new
-        self.class.metals.each { |app| @metals[app] = true }
-        freeze
-      end
-
-      def call(env)
-        @metals.keys.each do |app|
-          result = app.call(env)
-          return result unless @pass_through_on.include?(result[0].to_i)
-        end
-        @app.call(env)
-      end
-    end
-  end
-end

railties/test/application/metal_test.rb

@@ -37,7 +37,7 @@ module ApplicationTests
       app_file 'app/metal/metal_a.rb', <<-RUBY
         class MetalA
           def self.call(env)
-            [404, { "Content-Type" => "text/html"}, ["Metal A"]]
+            [404, { "Content-Type" => "text/html", "X-Cascade" => "pass" }, ["Metal A"]]
           end
         end
       RUBY
@@ -59,7 +59,7 @@ module ApplicationTests
       app_file 'app/metal/foo_metal.rb', <<-RUBY
         class FooMetal
           def self.call(env)
-            [404, { "Content-Type" => "text/html"}, ["Not Found"]]
+            [404, { "Content-Type" => "text/html", "X-Cascade" => "pass" }, ["Not Found"]]
           end
         end
       RUBY

railties/test/application/middleware_test.rb

@@ -20,6 +20,7 @@ module ApplicationTests
         "ActionDispatch::ShowExceptions",
         "ActionDispatch::Callbacks",
         "ActionDispatch::Session::CookieStore",
+        "ActionDispatch::Cascade",
         "ActionDispatch::ParamsParser",
         "Rack::MethodOverride",
         "Rack::Head",