From a81add5d96a027fc96e5f5f164b26aa62e6133c8 Mon Sep 17 00:00:00 2001
From: Will Norris <will@willnorris.com>
Date: Sat, 22 Jan 2022 10:29:37 -0800
Subject: [PATCH] lint: improve error handling

---
 .golangci.yml                 | 1 +
 cmd/imageproxy-sign/main.go   | 2 +-
 cmd/imageproxy/main.go        | 2 +-
 imageproxy.go                 | 2 +-
 internal/gcscache/gcscache.go | 3 ++-
 internal/s3cache/s3cache.go   | 4 +++-
 6 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index fb41023..d08bcd5 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -2,6 +2,7 @@ linters:
   enable:
     - dogsled
     - dupl
+    - errorlint
     - goimports
     - gosec
     - misspell
diff --git a/cmd/imageproxy-sign/main.go b/cmd/imageproxy-sign/main.go
index 5024b20..3233418 100644
--- a/cmd/imageproxy-sign/main.go
+++ b/cmd/imageproxy-sign/main.go
@@ -53,7 +53,7 @@ func sign(key string, s string, urlOnly bool) ([]byte, error) {
 
 	k, err := parseKey(key)
 	if err != nil {
-		return nil, fmt.Errorf("error parsing key: %v", err)
+		return nil, fmt.Errorf("error parsing key: %w", err)
 	}
 
 	mac := hmac.New(sha256.New, k)
diff --git a/cmd/imageproxy/main.go b/cmd/imageproxy/main.go
index 7bf3f55..68bf2ae 100644
--- a/cmd/imageproxy/main.go
+++ b/cmd/imageproxy/main.go
@@ -161,7 +161,7 @@ func parseCache(c string) (imageproxy.Cache, error) {
 
 	u, err := url.Parse(c)
 	if err != nil {
-		return nil, fmt.Errorf("error parsing cache flag: %v", err)
+		return nil, fmt.Errorf("error parsing cache flag: %w", err)
 	}
 
 	switch u.Scheme {
diff --git a/imageproxy.go b/imageproxy.go
index a5686cd..37a779f 100644
--- a/imageproxy.go
+++ b/imageproxy.go
@@ -276,7 +276,7 @@ func (p *Proxy) serveImage(w http.ResponseWriter, r *http.Request) {
 // the content type.  Returns empty string if error occurs.
 func peekContentType(p *bufio.Reader) string {
 	byt, err := p.Peek(512)
-	if err != nil && err != bufio.ErrBufferFull && err != io.EOF {
+	if err != nil && !errors.Is(err, bufio.ErrBufferFull) && !errors.Is(err, io.EOF) {
 		return ""
 	}
 	return http.DetectContentType(byt)
diff --git a/internal/gcscache/gcscache.go b/internal/gcscache/gcscache.go
index 6eda139..951b334 100644
--- a/internal/gcscache/gcscache.go
+++ b/internal/gcscache/gcscache.go
@@ -9,6 +9,7 @@ import (
 	"context"
 	"crypto/md5"
 	"encoding/hex"
+	"errors"
 	"io"
 	"io/ioutil"
 	"log"
@@ -27,7 +28,7 @@ type cache struct {
 func (c *cache) Get(key string) ([]byte, bool) {
 	r, err := c.object(key).NewReader(ctx)
 	if err != nil {
-		if err != storage.ErrObjectNotExist {
+		if !errors.Is(err, storage.ErrObjectNotExist) {
 			log.Printf("error reading from gcs: %v", err)
 		}
 		return nil, false
diff --git a/internal/s3cache/s3cache.go b/internal/s3cache/s3cache.go
index abfd28a..cdf38d0 100644
--- a/internal/s3cache/s3cache.go
+++ b/internal/s3cache/s3cache.go
@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"crypto/md5"
 	"encoding/hex"
+	"errors"
 	"io"
 	"io/ioutil"
 	"log"
@@ -36,7 +37,8 @@ func (c *cache) Get(key string) ([]byte, bool) {
 
 	resp, err := c.GetObject(input)
 	if err != nil {
-		if aerr, ok := err.(awserr.Error); ok && aerr.Code() != "NoSuchKey" {
+		var aerr awserr.Error
+		if errors.As(err, &aerr) && aerr.Code() != "NoSuchKey" {
 			log.Printf("error fetching from s3: %v", aerr)
 		}
 		return nil, false