Use application's generators defaults as engine defaults to not force users to manually set it

activerecord/lib/active_record/railtie.rb

@@ -14,7 +14,7 @@ class Railtie < Rails::Railtie
     config.active_record = ActiveSupport::OrderedOptions.new
 
     config.app_generators.orm :active_record, :migration => true,
-                                          :timestamps => true
+                                              :timestamps => true
 
     config.app_middleware.insert_after "::ActionDispatch::Callbacks",
       "ActiveRecord::QueryCache"

railties/lib/rails/engine/configuration.rb

@@ -10,6 +10,7 @@ class Configuration < ::Rails::Railtie::Configuration
       def initialize(root=nil)
         super()
         @root = root
+        @generators = app_generators
       end
 
       # Returns the middleware stack for the engine.

railties/test/railties/engine_test.rb

@@ -685,5 +685,22 @@ class Engine < ::Rails::Engine
       assert_equal :haml      , generators[:template_engine]
       assert_equal :rspec     , generators[:test_framework]
     end
+
+    test "engine should get default generators with ability to overwrite them" do
+      @plugin.write "lib/bukkits.rb", <<-RUBY
+        module Bukkits
+          class Engine < ::Rails::Engine
+            config.generators.test_framework :rspec
+          end
+        end
+      RUBY
+
+      boot_rails
+      require "#{rails_root}/config/environment"
+
+      generators = Bukkits::Engine.config.generators.options[:rails]
+      assert_equal :active_record, generators[:orm]
+      assert_equal :rspec        , generators[:test_framework]
+    end
   end
 end