1 files changed, 42 insertions, 6 deletions
diff --git a/railties/lib/rails/railtie/configuration.rb b/railties/lib/rails/railtie/configuration.rb
index 16eccaccc4..f57d82a3d8 100644
--- a/railties/lib/rails/railtie/configuration.rb
+++ b/railties/lib/rails/railtie/configuration.rb
@@ -3,10 +3,50 @@ require 'rails/configuration'
 module Rails
   class Railtie
     class Configuration
+      class MiddlewareStackProxy
+        def initialize
+          @operations = []
+        end
+
+        def insert_before(*args, &block)
+          @operations << [:insert_before, args, block]
+        end
+
+        alias insert insert_before
+
+        def insert_after(*args, &block)
+          @operations << [:insert_after, args, block]
+        end
+
+        def swap(*args, &block)
+          @operations << [:swap, args, block]
+        end
+
+        def use(*args, &block)
+          @operations << [:use, args, block]
+        end
+
+        def merge_into(other)
+          @operations.each do |operation, args, block|
+            other.send(operation, *args, &block)
+          end
+          other
+        end
+      end
+
       def initialize
         @@options ||= {}
       end
 
+      # This allows you to modify the application's middlewares from Engines.
+      #
+      # All operations you run on the app_middleware will be replayed on the
+      # application once it is defined and the default_middlewares are
+      # created
+      def app_middleware
+        @@app_middleware ||= MiddlewareStackProxy.new
+      end
+
       # Holds generators configuration:
       #
       #   config.generators do |g|
@@ -28,12 +68,8 @@ module Rails
         end
       end
 
-      def after_initialize_blocks
-        @@after_initialize_blocks ||= []
-      end
-
-      def after_initialize(&blk)
-        after_initialize_blocks << blk if blk
+      def after_initialize(&block)
+        ActiveSupport.on_load(:after_initialize, :yield => true, &block)
       end
 
       def to_prepare_blocks