Go oapi-codegen chi subrouters

Wed, Jan 25, 2023 2-minute read

Go oapi-codegen chi subrouters

I’m experimenting with open-api code generation. So far its pretty positive; write some yaml and it generates a bunch of interfaces. Those interfaces are where you write the handler business logic. It’ll handle missing data in and out and error if so.

As a chi user I’ve started making a simple todo app to test it all out. I was disappointed to learn that oapi-codegen doesn’t create the swagger UI for you but it will render the yaml file for you.

Except it doesn’t work out of the box for chi. In fact no other endpoint works - only those specified the specification.

To get around this you must create a subrouter and use that to do the specification validation else it’ll always fail for other routes. It makes sense in the end.

This is how I’ve done it in a simple way.

func main() {
	logger := httplog.NewLogger("mudmap", httplog.Options{
		JSON:     false,
		Concise:  true,
		LogLevel: "DEBUG",
	logger = logger.With().Caller().Logger()
	swagger, err := spec.GetSwagger()
	if err != nil {
		_, _ = fmt.Fprintf(os.Stderr, "Error loading swagger spec\n: %s", err)
	swagger.Servers = nil
	si := spec.NewTodoStore()

	r := chi.NewRouter()
	r.Get("/docs", func(w http.ResponseWriter, r *http.Request) {
  // Add n number of non-specification endpoints. But use sparingly.

	r.Mount("/", subRouter(swagger))

	spec.HandlerFromMux(si, r)

	s := &http.Server{
		Handler: r,
		Addr:    fmt.Sprintf(""),

	log.Println("starting server")

// subRouter holds the oapi-codegen validators which are 
// mounted to the parent chi router.
func subRouter(s *openapi3.T) http.Handler {
	r := chi.NewRouter()
	return r


#chi #go #openapi #codegen