how to get full router path in middleware?

[bestgopher]

I want to get full router path in middleware before calling the handler.

[bestgopher]

like gin's ctx.FullPath() method

[js-everts]

Maybe with RoutePattern()?

chi.RouteContext(r.Context()).RoutePattern()

[bestgopher]

Maybe with RoutePattern()?

chi.RouteContext(r.Context()).RoutePattern()

I tried it, but failed. it only got /test1/* in my example.

[js-everts]

Apologies. I misunderstood you.

I am not that familiar with chi's internals. But I'm guessing what you want is not possible because of the way chi does routing. Since its based on a trie data structure, a middleware will have no knowledge of the full route pattern high up in the trie because chi has not yet resolved the full route pattern at this point in time. However if you were to attach the middleware as close to the final handlers as possible, then this could work. But that would mean attaching the middleware to every route handler using With().

For example something like the following. This will print /foo/bar/{slug} and /foo/baz/{slug} when calling the respective paths.

func PrintPattern(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		fmt.Println(chi.RouteContext(r.Context()).RoutePattern())
		next.ServeHTTP(w, r)
	}

	return http.HandlerFunc(fn)
}

func main() {
	r := chi.NewRouter()

	r.Route("/foo", func(r chi.Router) {
		r.With(PrintPattern).Get("/bar/{slug}", func(rw http.ResponseWriter, r *http.Request) {
			rw.Write([]byte("hello"))
		})

		r.With(PrintPattern).Get("/baz/{slug}", func(rw http.ResponseWriter, r *http.Request) {
			rw.Write([]byte("hello"))
		})
	})

	http.ListenAndServe(":3000", r)
}

[pkieltyka]

hey all, the pattern is determined at runtime as the request is traversing the router. As a result, you need to fetch the pattern after the call to next.ServeHTTP, see https://github.com/go-chi/chi/blob/master/context.go#L117-L118