feat: recoverer middleware

middlewarex/recoverer.go

@@ -0,0 +1,40 @@
+package middlewarex
+
+import (
+	"errors"
+	"net/http"
+)
+
+type ErrorHandler func(w http.ResponseWriter, r *http.Request, err error)
+
+func Recoverer(errorHandler ErrorHandler) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+			defer func() {
+				if rvr := recover(); rvr != nil {
+					if rvr == http.ErrAbortHandler {
+						// Don’t recover http.ErrAbortHandler so the response to
+						// the client is aborted.
+						panic(rvr)
+					}
+
+					var err error
+					switch x := rvr.(type) {
+					case string:
+						err = errors.New(x)
+					case error:
+						err = x
+					default:
+						err = errors.New("unknown panic")
+					}
+
+					errorHandler(w, r, err)
+				}
+			}()
+
+			next.ServeHTTP(w, r)
+		}
+
+		return http.HandlerFunc(fn)
+	}
+}

middlewarex/recoverer_test.go

@@ -0,0 +1,47 @@
+package middlewarex
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRecovererAbortHandler(t *testing.T) {
+	defer func() {
+		rcv := recover()
+		if rcv != http.ErrAbortHandler {
+			t.Fatalf("http.ErrAbortHandler should not be recovered")
+		}
+	}()
+
+	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		panic(http.ErrAbortHandler)
+	})
+
+	h := Recoverer(nil)(next)
+	r := httptest.NewRequest(http.MethodGet, "/", nil)
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, r)
+}
+
+func TestRecovererCustomErrorResponse(t *testing.T) {
+	plainTextErrorHandler := func(w http.ResponseWriter, r *http.Request, err error) {
+		w.WriteHeader(http.StatusInternalServerError)
+		_, _ = w.Write([]byte("internal server error: " + err.Error()))
+	}
+
+	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		panic("test panic")
+	})
+
+	h := Recoverer(plainTextErrorHandler)(next)
+	r := httptest.NewRequest(http.MethodGet, "/", nil)
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, r)
+
+	res := w.Result()
+	assert.Equal(t, res.StatusCode, http.StatusInternalServerError)
+	assert.Equal(t, w.Body.String(), "internal server error: test panic")
+}