Move assets route internal decoration.

We can't depend on assets_prefix outside sprockets.

Author: arthurnn

lib/sprockets/rails/route_wrapper.rb

@@ -0,0 +1,19 @@
+module Sprockets
+  module Rails
+    module RouteWrapper
+      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}
+          end
+          alias_method_chain :internal?, :sprockets
+        end
+      end
+    end
+  end
+end

lib/sprockets/railtie.rb

@@ -6,6 +6,7 @@
 require 'sprockets'
 require 'sprockets/rails/context'
 require 'sprockets/rails/helper'
+require 'sprockets/rails/route_wrapper'
 require 'sprockets/rails/version'
 
 module Rails
@@ -146,6 +147,12 @@ def self.build_manifest(app)
       end
       app.assets_manifest = build_manifest(app)
 
+      ActionDispatch::Routing::RouteWrapper.class_eval do
+        include Sprockets::Rails::RouteWrapper
+
+        self.assets_prefix = config.assets.prefix
+      end
+
       ActiveSupport.on_load(:action_view) do
         include Sprockets::Rails::Helper