Don't reference Rails.application from inside a component

actionpack/lib/action_dispatch/middleware/reloader.rb

@@ -33,26 +33,22 @@ def self.to_cleanup(*args, &block)
     end
 
     def self.prepare!
-      if defined? Rails.application.reloader
-        Rails.application.reloader.prepare!
-      else
-        ActiveSupport::Reloader.prepare!
-      end
+      default_reloader.prepare!
     end
 
     def self.cleanup!
-      if defined? Rails.application.reloader
-        Rails.application.reloader.reload!
-      else
-        ActiveSupport::Reloader.reload!
-      end
+      default_reloader.reload!
     end
 
     class << self
+      attr_accessor :default_reloader # :nodoc:
+
       deprecate to_prepare: 'use ActiveSupport::Reloader.to_prepare instead',
         to_cleanup: 'use ActiveSupport::Reloader.to_complete instead',
         prepare!: 'use Rails.application.reloader.prepare! instead',
         cleanup!: 'use Rails.application.reloader.reload! instead of cleanup + prepare'
     end
+
+    self.default_reloader = ActiveSupport::Reloader
   end
 end

actionpack/lib/action_dispatch/railtie.rb

@@ -39,6 +39,8 @@ class Railtie < Rails::Railtie # :nodoc:
       config.action_dispatch.always_write_cookie = Rails.env.development? if config.action_dispatch.always_write_cookie.nil?
       ActionDispatch::Cookies::CookieJar.always_write_cookie = config.action_dispatch.always_write_cookie
 
+      ActionDispatch::Reloader.default_reloader = app.reloader
+
       ActionDispatch.test_app = app
     end
   end