From 0c4e8aeb2b32d576f2408c888792721fbc5bd1f2 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Wed, 1 Jul 2020 00:02:02 +0300
Subject: [PATCH] all: use `errors.As` for inspecting errors that implement
 httpserver.ErrorWithStatusCode

---
 app/vmselect/main.go         | 4 +++-
 lib/httpserver/httpserver.go | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/app/vmselect/main.go b/app/vmselect/main.go
index 097fd59c7..837fec506 100644
--- a/app/vmselect/main.go
+++ b/app/vmselect/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"net/http"
@@ -318,7 +319,8 @@ func sendPrometheusError(w http.ResponseWriter, r *http.Request, err error) {
 
 	w.Header().Set("Content-Type", "application/json")
 	statusCode := http.StatusUnprocessableEntity
-	if esc, ok := err.(*httpserver.ErrorWithStatusCode); ok {
+	var esc *httpserver.ErrorWithStatusCode
+	if errors.As(err, &esc) {
 		statusCode = esc.StatusCode
 	}
 	w.WriteHeader(statusCode)
diff --git a/lib/httpserver/httpserver.go b/lib/httpserver/httpserver.go
index c4930c809..739b31d91 100644
--- a/lib/httpserver/httpserver.go
+++ b/lib/httpserver/httpserver.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"context"
 	"crypto/tls"
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -436,8 +437,9 @@ func Errorf(w http.ResponseWriter, format string, args ...interface{}) {
 
 	// Extract statusCode from args
 	statusCode := http.StatusBadRequest
+	var esc *ErrorWithStatusCode
 	for _, arg := range args {
-		if esc, ok := arg.(*ErrorWithStatusCode); ok {
+		if err, ok := arg.(error); ok && errors.As(err, &esc) {
 			statusCode = esc.StatusCode
 			break
 		}