bdns: replace direct type assertions with errors.As (letsencrypt#5122)

beautifulentropy · web-flow · commit feebb4017e7a · 2020-10-13T17:31:42.000-07:00
errors.As checks for a specific error in a wrapped error chain (see https://golang.org/pkg/errors/#As) as opposed to asserting that an error is of a specific type Part of letsencrypt#5010
diff --git a/bdns/dns_test.go b/bdns/dns_test.go
@@ -368,7 +368,8 @@ func TestDNSLookupHost(t *testing.T) {
 	t.Logf("%s - IP: %s, Err: %s", hostname, ip, err)
 	test.AssertError(t, err, "Should be an error")
 	expectedErr := DNSError{dns.TypeA, hostname, nil, dns.RcodeRefused}
-	if err, ok := err.(*DNSError); !ok || *err != expectedErr {
+	var dnserr *DNSError
+	if !(errors.As(err, &dnserr) && *dnserr == expectedErr) {
 		t.Errorf("Looking up %s, got %#v, expected %#v", hostname, err, expectedErr)
 	}
 }
@@ -379,13 +380,14 @@ func TestDNSNXDOMAIN(t *testing.T) {
 	hostname := "nxdomain.letsencrypt.org"
 	_, err := obj.LookupHost(context.Background(), hostname)
 	expected := DNSError{dns.TypeA, hostname, nil, dns.RcodeNameError}
-	if err, ok := err.(*DNSError); !ok || *err != expected {
+	var dnserr *DNSError
+	if !(errors.As(err, &dnserr) && *dnserr == expected) {
 		t.Errorf("Looking up %s, got %#v, expected %#v", hostname, err, expected)
 	}
 
 	_, err = obj.LookupTXT(context.Background(), hostname)
 	expected.recordType = dns.TypeTXT
-	if err, ok := err.(*DNSError); !ok || *err != expected {
+	if !(errors.As(err, &dnserr) && *dnserr == expected) {
 		t.Errorf("Looking up %s, got %#v, expected %#v", hostname, err, expected)
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -368,7 +368,8 @@ func TestDNSLookupHost(t *testing.T) {`
`368`	`368`	`t.Logf("%s - IP: %s, Err: %s", hostname, ip, err)`
`369`	`369`	`test.AssertError(t, err, "Should be an error")`
`370`	`370`	`expectedErr := DNSError{dns.TypeA, hostname, nil, dns.RcodeRefused}`
`371`		`- if err, ok := err.(DNSError); !ok \|\| err != expectedErr {`
	`371`	`+ var dnserr *DNSError`
	`372`	`+ if !(errors.As(err, &dnserr) && *dnserr == expectedErr) {`
`372`	`373`	`t.Errorf("Looking up %s, got %#v, expected %#v", hostname, err, expectedErr)`
`373`	`374`	`}`
`374`	`375`	`}`
`@@ -379,13 +380,14 @@ func TestDNSNXDOMAIN(t *testing.T) {`
`379`	`380`	`hostname := "nxdomain.letsencrypt.org"`
`380`	`381`	`_, err := obj.LookupHost(context.Background(), hostname)`
`381`	`382`	`expected := DNSError{dns.TypeA, hostname, nil, dns.RcodeNameError}`
`382`		`- if err, ok := err.(DNSError); !ok \|\| err != expected {`
	`383`	`+ var dnserr *DNSError`
	`384`	`+ if !(errors.As(err, &dnserr) && *dnserr == expected) {`
`383`	`385`	`t.Errorf("Looking up %s, got %#v, expected %#v", hostname, err, expected)`
`384`	`386`	`}`
`385`	`387`
`386`	`388`	`_, err = obj.LookupTXT(context.Background(), hostname)`
`387`	`389`	`expected.recordType = dns.TypeTXT`
`388`		`- if err, ok := err.(DNSError); !ok \|\| err != expected {`
	`390`	`+ if !(errors.As(err, &dnserr) && *dnserr == expected) {`
`389`	`391`	`t.Errorf("Looking up %s, got %#v, expected %#v", hostname, err, expected)`
`390`	`392`	`}`
`391`	`393`	`}`