class ActionDispatch::Routing::RoutesInspector

def collect_engine_routes(route)
  name = route.endpoint
  return unless route.engine?
  return if @engines[name]
  routes = route.rack_app.routes
  if routes.is_a?(ActionDispatch::Routing::RouteSet)
    @engines[name] = collect_routes(routes.routes)
  end
end