Enumerate deferred scripts with a sprockets helper

app/views/common/_discourse_javascript.html.erb

@@ -1,11 +1,7 @@
 <script>
   window.assetPath = (function(){
 
-    // TODO: automate this to grab from the manifest, Rails voodoo should be able to get it
-    var map = {
-      'defer/html-sanitizer-bundle': <%= asset_path('defer/html-sanitizer-bundle.js').inspect.html_safe %>,
-      'defer/google_diff_match_patch': <%= asset_path('defer/google_diff_match_patch.js').inspect.html_safe %>
-    };
+    var map = <%= deferred_javascripts %>;
 
     return function(asset){ return map[asset]; };
   })();

config/initializers/deferred_javascripts_helper.rb

@@ -0,0 +1,20 @@
+module DeferredJavascriptsHelper
+
+  # Provides a javascript map of the files in the 'defer' directory
+  def deferred_javascripts
+    files = {}
+
+    Dir.glob("#{Rails.root}/app/assets/javascripts/defer/*.js").each do |file|
+      module_name = "defer/#{File.basename(file, '.js')}"
+      file_name = asset_path("defer/#{File.basename(file)}")
+      files[module_name] = file_name
+    end
+
+    return files.to_json.html_safe
+  end
+
+end
+
+module Sprockets::Rails::Helper
+  include DeferredJavascriptsHelper
+end