Fix debug pprof handler routing

[jace-ys]

Hey folks 👋🏻 Just started using goa.design and I really like it so far!

While using the clue debug handlers, I noticed that the pprof profile handlers like goroutine and mutex, other than cmdline, profile, symbol and trace, were not actually working and returned 404.

After some digging and testing, it seems that's because those profile handlers are not explicitly mounted on the mux. While this works for http.NewServeMux (like in debug_test.go), it doesn't actually work with chi.Mux or even gorilla mux.Router - not entirely sure why, but I'd bet it's something to do with how routing decisions are implemented in the stdlib vs. third-party libraries.

You can see that here in this test:

type ChiMuxWrapper struct {
	*chi.Mux
}

func (w *ChiMuxWrapper) HandleFunc(pattern string, handler func(http.ResponseWriter, *http.Request)) {
	w.Mux.HandleFunc(pattern, handler)
}

func TestMountPprofHandlers(t *testing.T) {
	mux := chi.NewRouter()
	MountPprofHandlers(&ChiMuxWrapper{mux})
	MountPprofHandlers(&ChiMuxWrapper{mux}, WithPrefix("test"))
	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/" {
			w.WriteHeader(http.StatusNotFound)
			return
		}
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("OK")) // nolint: errcheck
	})
	mux.Handle("/", handler)
	ts := httptest.NewServer(mux)
	defer ts.Close()

	status, resp := makeRequest(t, ts.URL)
	if status != http.StatusOK {
		t.Errorf("got status %d, expected %d", status, http.StatusOK)
	}
	if resp != "OK" {
		t.Errorf("got body %q, expected %q", resp, "OK")
	}

	paths := []string{
		"/debug/pprof/",
		"/test/",
		"/debug/pprof/allocs",
		"/debug/pprof/block",
		"/debug/pprof/cmdline",
		"/debug/pprof/goroutine",
		"/debug/pprof/heap",
		"/debug/pprof/mutex",
		// "/debug/pprof/profile?seconds=1", # Takes too long to run on each test
		"/debug/pprof/symbol",
		"/debug/pprof/threadcreate",
		// "/debug/pprof/trace", # Takes too long to run on each test
	}
	for _, path := range paths {
		status, resp = makeRequest(t, ts.URL+path)
		if status != http.StatusOK {
			t.Errorf("got status %d, expected %d", status, http.StatusOK)
		}
		if resp == "" {
			t.Errorf("got body %q, expected non-empty", resp)
		}
	}
}

I've proposed a fix for this by explicitly mounting each pprof handler, similar to what chi's middleware.Profiler does: https://github.com/go-chi/chi/blob/master/middleware/profiler.go

Let me know what you think!

[raphael]

Thank you for raising this issue and the great PR. It all makes sense. I've fixed the lint issue introduced by upgrading the linter tool in the main branch. Would you mind rebasing your PR on top? Thank you!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.79%. Comparing base (59e3094) to head (7ba93a3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #446      +/-   ##
==========================================
+ Coverage   85.74%   85.79%   +0.04%     
==========================================
  Files          36       36              
  Lines        1747     1753       +6     
==========================================
+ Hits         1498     1504       +6     
  Misses        225      225              
  Partials       24       24              

Flag	Coverage Δ
micro	85.79% <100.00%> (+0.04%)	⬆️

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[jace-ys]

Thank you for raising this issue and the great PR. It all makes sense. I've fixed the lint issue introduced by upgrading the linter tool in the main branch. Would you mind rebasing your PR on top? Thank you!

Done!

[raphael]

Thank you!