No need for a module if it's only being included once into an empty class.

railties/lib/rails/configuration.rb

@@ -4,100 +4,6 @@ require 'rails/rack'
 
 module Rails
   module Configuration
-    module Shared
-      def middleware
-        @@default_middleware_stack ||= default_middleware
-      end
-
-      # Holds generators configuration:
-      #
-      #   config.generators do |g|
-      #     g.orm             :datamapper, :migration => true
-      #     g.template_engine :haml
-      #     g.test_framework  :rspec
-      #   end
-      #
-      # If you want to disable color in console, do:
-      #
-      #   config.generators.colorize_logging = false
-      #
-      def generators
-        @@generators ||= Rails::Configuration::Generators.new
-        if block_given?
-          yield @@generators
-        else
-          @@generators
-        end
-      end
-
-      def after_initialize_blocks
-        @@after_initialize_blocks ||= []
-      end
-
-      def after_initialize(&blk)
-        after_initialize_blocks << blk if blk
-      end
-
-      def to_prepare_blocks
-        @@to_prepare_blocks ||= []
-      end
-
-      def to_prepare(&blk)
-        to_prepare_blocks << blk if blk
-      end
-
-      def respond_to?(name)
-        super || name.to_s =~ config_key_regexp
-      end
-
-      def metal_loader
-        @metal_loader ||= Rails::Application::MetalLoader.new
-      end
-
-    private
-
-      def method_missing(name, *args, &blk)
-        if name.to_s =~ config_key_regexp
-          return $2 == '=' ? options[$1] = args.first : options[$1]
-        end
-        super
-      end
-
-      def config_key_regexp
-        bits = config_keys.map { |n| Regexp.escape(n.to_s) }.join('|')
-        /^(#{bits})(?:=)?$/
-      end
-
-      def config_keys
-        (Railtie.railtie_names + Engine.engine_names).map { |n| n.to_s }.uniq
-      end
-
-      def options
-        @@options ||= Hash.new { |h,k| h[k] = ActiveSupport::OrderedOptions.new }
-      end
-
-      def default_middleware
-        require 'action_dispatch'
-        ActionDispatch::MiddlewareStack.new.tap do |middleware|
-          middleware.use('::ActionDispatch::Static', lambda { Rails.public_path }, :if => lambda { serve_static_assets })
-          middleware.use('::Rack::Lock', :if => lambda { !allow_concurrency })
-          middleware.use('::Rack::Runtime')
-          middleware.use('::Rails::Rack::Logger')
-          middleware.use('::ActionDispatch::ShowExceptions', lambda { consider_all_requests_local })
-          middleware.use("::ActionDispatch::RemoteIp", lambda { action_dispatch.ip_spoofing_check }, lambda { action_dispatch.trusted_proxies })
-          middleware.use('::Rack::Sendfile', lambda { action_dispatch.x_sendfile_header })
-          middleware.use('::ActionDispatch::Callbacks', lambda { !cache_classes })
-          middleware.use('::ActionDispatch::Cookies')
-          middleware.use(lambda { ActionController::SessionManagement.session_store_for(action_controller.session_store) }, lambda { action_controller.session })
-          middleware.use('::ActionDispatch::Flash', :if => lambda { action_controller.session_store })
-          middleware.use(lambda { metal_loader.build_middleware(metals) }, :if => lambda { metal_loader.metals.any? })
-          middleware.use('ActionDispatch::ParamsParser')
-          middleware.use('::Rack::MethodOverride')
-          middleware.use('::ActionDispatch::Head')
-        end
-      end
-    end
-
     class Generators #:nodoc:
       attr_accessor :aliases, :options, :templates, :fallbacks, :colorize_logging
 

railties/lib/rails/railtie/configuration.rb

@@ -3,7 +3,97 @@ require 'rails/configuration'
 module Rails
   class Railtie
     class Configuration
-      include Rails::Configuration::Shared
+      def middleware
+        @@default_middleware_stack ||= default_middleware
+      end
+
+      # Holds generators configuration:
+      #
+      #   config.generators do |g|
+      #     g.orm             :datamapper, :migration => true
+      #     g.template_engine :haml
+      #     g.test_framework  :rspec
+      #   end
+      #
+      # If you want to disable color in console, do:
+      #
+      #   config.generators.colorize_logging = false
+      #
+      def generators
+        @@generators ||= Rails::Configuration::Generators.new
+        if block_given?
+          yield @@generators
+        else
+          @@generators
+        end
+      end
+
+      def after_initialize_blocks
+        @@after_initialize_blocks ||= []
+      end
+
+      def after_initialize(&blk)
+        after_initialize_blocks << blk if blk
+      end
+
+      def to_prepare_blocks
+        @@to_prepare_blocks ||= []
+      end
+
+      def to_prepare(&blk)
+        to_prepare_blocks << blk if blk
+      end
+
+      def respond_to?(name)
+        super || name.to_s =~ config_key_regexp
+      end
+
+      def metal_loader
+        @metal_loader ||= Rails::Application::MetalLoader.new
+      end
+
+    private
+
+      def method_missing(name, *args, &blk)
+        if name.to_s =~ config_key_regexp
+          return $2 == '=' ? options[$1] = args.first : options[$1]
+        end
+        super
+      end
+
+      def config_key_regexp
+        bits = config_keys.map { |n| Regexp.escape(n.to_s) }.join('|')
+        /^(#{bits})(?:=)?$/
+      end
+
+      def config_keys
+        (Railtie.railtie_names + Engine.engine_names).map { |n| n.to_s }.uniq
+      end
+
+      def options
+        @@options ||= Hash.new { |h,k| h[k] = ActiveSupport::OrderedOptions.new }
+      end
+
+      def default_middleware
+        require 'action_dispatch'
+        ActionDispatch::MiddlewareStack.new.tap do |middleware|
+          middleware.use('::ActionDispatch::Static', lambda { Rails.public_path }, :if => lambda { serve_static_assets })
+          middleware.use('::Rack::Lock', :if => lambda { !allow_concurrency })
+          middleware.use('::Rack::Runtime')
+          middleware.use('::Rails::Rack::Logger')
+          middleware.use('::ActionDispatch::ShowExceptions', lambda { consider_all_requests_local })
+          middleware.use("::ActionDispatch::RemoteIp", lambda { action_dispatch.ip_spoofing_check }, lambda { action_dispatch.trusted_proxies })
+          middleware.use('::Rack::Sendfile', lambda { action_dispatch.x_sendfile_header })
+          middleware.use('::ActionDispatch::Callbacks', lambda { !cache_classes })
+          middleware.use('::ActionDispatch::Cookies')
+          middleware.use(lambda { ActionController::SessionManagement.session_store_for(action_controller.session_store) }, lambda { action_controller.session })
+          middleware.use('::ActionDispatch::Flash', :if => lambda { action_controller.session_store })
+          middleware.use(lambda { metal_loader.build_middleware(metals) }, :if => lambda { metal_loader.metals.any? })
+          middleware.use('ActionDispatch::ParamsParser')
+          middleware.use('::Rack::MethodOverride')
+          middleware.use('::ActionDispatch::Head')
+        end
+      end
     end
   end
 end