Build an asset manifest for iD

app/helpers/asset_helper.rb

@@ -0,0 +1,11 @@
+module AssetHelper
+  def assets(directory)
+    assets = {}
+
+    Rails.application.assets.index.each_logical_path("#{directory}/*") do |path|
+      assets[path.sub(/^#{directory}\//, "")] = asset_path(path)
+    end
+
+    assets
+  end
+end

app/views/site/id.html.erb

@@ -21,6 +21,7 @@
     var id = iD()
       .embed(true)
       .assetPath("/assets/iD/") <%# Can't use asset_path('iD/') in production. %>
+      .assetMap(<%= assets("iD").to_json.html_safe %>)
       .locale("<%= locale %>", "<%= asset_path("iD/locales/#{locale}.json") %>")
       .preauth({
         <% token = @user.access_token(ID_KEY) %>