rails--rails/railties/lib/rails/application/routes_reloader.rb

module Rails
  class Application
    class RoutesReloader < ::ActiveSupport::FileUpdateChecker
      def initialize
        super([]) { reload! }
      end

      def blocks
        @blocks ||= {}
      end

      def reload!
        clear!
        load_blocks
        load_paths
        finalize!
      ensure
        revert
      end

    protected

      def clear!
        routers.each do |routes|
          routes.disable_clear_and_finalize = true
          routes.clear!
        end
      end

      def load_blocks
        blocks.each do |routes, block|
          routes.draw(&block) if block
        end
      end

      def load_paths
        paths.each { |path| load(path) }
      end

      def finalize!
        routers.each do |routes|
          ActiveSupport.on_load(:action_controller) { routes.finalize! }
        end
      end

      def revert
        routers.each do |routes|
          routes.disable_clear_and_finalize = false
        end
      end

      def routers
        blocks.keys
      end
    end
  end
end