Improve the registration of the Engines' assets path in propshaft

Author: rafaelfranca

lib/propshaft/railtie.rb

@@ -1,16 +1,6 @@
 require "rails"
-require "rails/railtie"
 require "active_support/ordered_options"
 
-# FIXME: There's gotta be a better way than this hack?
-class Rails::Engine < Rails::Railtie
-  initializer "propshaft.append_assets_path", group: :all do |app|
-    app.config.assets.paths.unshift(*paths["vendor/assets"].existent_directories)
-    app.config.assets.paths.unshift(*paths["lib/assets"].existent_directories)
-    app.config.assets.paths.unshift(*paths["app/assets"].existent_directories)
-  end
-end
-
 module Propshaft
   class Railtie < ::Rails::Railtie
     config.assets = ActiveSupport::OrderedOptions.new
@@ -23,6 +13,15 @@ class Railtie < ::Rails::Railtie
     ]
     config.assets.sweep_cache = Rails.env.development?
 
+    # Register propshaft initializer to copy the assets path in all the Rails Engines.
+    # This makes possible for us to keep all `assets` config in this Railtie, but still
+    # allow engines to automatically register their own paths.
+    Rails::Engine.initializer "propshaft.append_assets_path", group: :all do |app|
+      app.config.assets.paths.unshift(*paths["vendor/assets"].existent_directories)
+      app.config.assets.paths.unshift(*paths["lib/assets"].existent_directories)
+      app.config.assets.paths.unshift(*paths["app/assets"].existent_directories)
+    end
+
     config.after_initialize do |app|
       config.assets.output_path ||=
         Pathname.new(File.join(app.config.paths["public"].first, app.config.assets.prefix))