1 files changed, 67 insertions, 7 deletions

diff --git a/actionpack/lib/action_controller/middleware_stack.rb b/actionpack/lib/action_controller/middleware_stack.rb
index 1864bed23a..2bccba2ba1 100644
--- a/actionpack/lib/action_controller/middleware_stack.rb
+++ b/actionpack/lib/action_controller/middleware_stack.rb
@@ -1,14 +1,47 @@
 module ActionController
   class MiddlewareStack < Array
     class Middleware
-      attr_reader :klass, :args, :block
+      def self.new(klass, *args, &block)
+        if klass.is_a?(self)
+          klass
+        else
+          super
+        end
+      end
+
+      attr_reader :args, :block
 
       def initialize(klass, *args, &block)
-        @klass = klass.is_a?(Class) ? klass : klass.to_s.constantize
+        @klass = klass
+
+        options = args.extract_options!
+        if options.has_key?(:if)
+          @conditional = options.delete(:if)
+        else
+          @conditional = true
+        end
+        args << options unless options.empty?
+
         @args = args
         @block = block
       end
 
+      def klass
+        if @klass.is_a?(Class)
+          @klass
+        else
+          @klass.to_s.constantize
+        end
+      end
+
+      def active?
+        if @conditional.respond_to?(:call)
+          @conditional.call
+        else
+          @conditional
+        end
+      end
+
       def ==(middleware)
         case middleware
         when Middleware
@@ -21,22 +54,49 @@ module ActionController
       end
 
       def inspect
-        str = @klass.to_s
-        @args.each { |arg| str += ", #{arg.inspect}" }
+        str = klass.to_s
+        args.each { |arg| str += ", #{arg.inspect}" }
         str
       end
 
       def build(app)
-        klass.new(app, *args, &block)
+        if block
+          klass.new(app, *args, &block)
+        else
+          klass.new(app, *args)
+        end
       end
     end
 
+    def initialize(*args, &block)
+      super(*args)
+      block.call(self) if block_given?
+    end
+
+    def insert(index, *objs)
+      index = self.index(index) unless index.is_a?(Integer)
+      objs = objs.map { |obj| Middleware.new(obj) }
+      super(index, *objs)
+    end
+
+    alias_method :insert_before, :insert
+
+    def insert_after(index, *objs)
+      index = self.index(index) unless index.is_a?(Integer)
+      insert(index + 1, *objs)
+    end
+
     def use(*args, &block)
-      push(Middleware.new(*args, &block))
+      middleware = Middleware.new(*args, &block)
+      push(middleware)
+    end
+
+    def active
+      find_all { |middleware| middleware.active? }
     end
 
     def build(app)
-      reverse.inject(app) { |a, e| e.build(a) }
+      active.reverse.inject(app) { |a, e| e.build(a) }
     end
   end
 end