Use prepend when available

Author: arthurnn

lib/sprockets/rails/route_wrapper.rb

@@ -1,15 +1,19 @@
 module Sprockets
   module Rails
     module RouteWrapper
+
+      def internal_assets_path?
+        path =~ %r{\A#{self.class.assets_prefix}\z}
+      end
+
+      def internal?
+        super || internal_assets_path?
+      end
+
       def self.included(klass)
-        klass.class_attribute(:assets_prefix)
         klass.class_eval do
-          def assets_prefix
-            self.class.assets_prefix
-          end
-
           def internal_with_sprockets?
-            internal_without_sprockets? || path =~ %r{\A#{assets_prefix}\z}
+            internal_without_sprockets? || internal_assets_path?
           end
           alias_method_chain :internal?, :sprockets
         end

lib/sprockets/railtie.rb

@@ -148,7 +148,13 @@ def self.build_manifest(app)
       app.assets_manifest = build_manifest(app)
 
       ActionDispatch::Routing::RouteWrapper.class_eval do
-        include Sprockets::Rails::RouteWrapper
+        class_attribute :assets_prefix
+
+        if defined?(prepend) && ::Rails.version >= '4'
+          prepend Sprockets::Rails::RouteWrapper
+        else
+          include Sprockets::Rails::RouteWrapper
+        end
 
         self.assets_prefix = config.assets.prefix
       end