sprockets ignores extensions after .js in build mode. closes #110

features/sprockets.feature

@@ -14,3 +14,8 @@ Feature: Sprockets
     Given the Server is running at "test-app"
     When I go to "/javascripts/multiple_engines.js"
     Then I should see "Hello One"
+    
+  Scenario: Multiple engine files should build correctly
+    Given a built app at "test-app"
+    Then "javascripts/multiple_engines.js" should exist at "test-app" and include "Hello One"
+    And cleanup built app at "test-app"

lib/middleman/core_extensions/sprockets.rb

@@ -7,6 +7,18 @@ module Middleman::CoreExtensions::Sprockets
     def registered(app)
       app.set :js_compressor, false
       
+      # Cut off every extension after .js (which sprockets eats up)
+      app.build_reroute do |destination, request_path|
+        if !request_path.match(/\.js\./i)
+          false
+        else
+          [
+            destination.gsub(/\.js(\..*)$/, ".js"),
+            request_path.gsub(/\.js(\..*)$/, ".js")
+          ]
+        end
+      end
+      
       app.after_configuration do
         js_env = Middleman::CoreExtensions::Sprockets::JavascriptEnvironment.new(app)