[8.6](backport #33720) x-pack/filebeat/input/http_endpoint: canonicalise tls consistency error

x-pack/filebeat/input/http_endpoint/input.go

@@ -164,16 +164,32 @@ func (p *pool) serve(ctx v2.Context, e *httpEndpoint, pub stateless.Publisher) e
 }
 
 func checkTLSConsistency(addr string, old, new *tlscommon.ServerConfig) error {
+	if old == nil && new == nil {
+		return nil
+	}
 	if (old == nil) != (new == nil) {
-		return fmt.Errorf("inconsistent TLS usage on %s: mixed TLS and unencrypted", addr)
+		return invalidTLSStateErr{addr: addr, reason: "mixed TLS and unencrypted", old: old, new: new}
 	}
 	if !reflect.DeepEqual(old, new) {
-		return fmt.Errorf("inconsistent TLS configuration on %s: configuration options do not agree: old=%s new=%s",
-			addr, renderTLSConfig(old), renderTLSConfig(new))
+		return invalidTLSStateErr{addr: addr, reason: "configuration options do not agree", old: old, new: new}
 	}
 	return nil
 }
 
+type invalidTLSStateErr struct {
+	addr     string
+	reason   string
+	old, new *tlscommon.ServerConfig
+}
+
+func (e invalidTLSStateErr) Error() string {
+	if e.old == nil || e.new == nil {
+		return fmt.Sprintf("inconsistent TLS usage on %s: %s", e.addr, e.reason)
+	}
+	return fmt.Sprintf("inconsistent TLS configuration on %s: %s: old=%s new=%s",
+		e.addr, e.reason, renderTLSConfig(e.old), renderTLSConfig(e.new))
+}
+
 func renderTLSConfig(tls *tlscommon.ServerConfig) string {
 	c, err := conf.NewConfigFrom(tls)
 	if err != nil {

x-pack/filebeat/input/http_endpoint/input_test.go

@@ -162,7 +162,7 @@ var serverPoolTests = []struct {
 				},
 			},
 		},
-		wantErr: errors.New("inconsistent TLS usage on 127.0.0.1:9001: mixed TLS and unencrypted"),
+		wantErr: invalidTLSStateErr{addr: "127.0.0.1:9001", reason: "mixed TLS and unencrypted"},
 	},
 	{
 		name: "inconsistent_tls_config",
@@ -198,10 +198,7 @@ var serverPoolTests = []struct {
 				},
 			},
 		},
-		wantErr: errors.New(`inconsistent TLS configuration on 127.0.0.1:9001: ` +
-			`configuration options do not agree: ` +
-			`old={"ca_sha256":[],"certificate":"","certificate_authorities":[],"cipher_suites":[],"client_authentication":0,"curve_types":[],"key":"","key_passphrase":"","supported_protocols":[],"verification_mode":1} ` +
-			`new={"ca_sha256":[],"certificate":"","certificate_authorities":[],"cipher_suites":[],"client_authentication":0,"curve_types":[],"key":"","key_passphrase":"","supported_protocols":[],"verification_mode":3}`),
+		wantErr: invalidTLSStateErr{addr: "127.0.0.1:9001", reason: "configuration options do not agree"},
 	},
 }
 
@@ -241,7 +238,7 @@ func TestServerPool(t *testing.T) {
 			case err := <-fails:
 				if test.wantErr == nil {
 					t.Errorf("unexpected error calling serve: %#q", err)
-				} else if test.wantErr.Error() != err.Error() {
+				} else if !errors.Is(err, test.wantErr) {
 					t.Errorf("unexpected error calling serve: got=%#q, want=%#q", err, test.wantErr)
 				}
 			default:
@@ -272,6 +269,18 @@ func TestServerPool(t *testing.T) {
 	}
 }
 
+// Is is included to simplify testing, but is not exposed to avoid unwanted error
+// matching outside tests.
+func (e invalidTLSStateErr) Is(err error) bool {
+	if err, ok := err.(invalidTLSStateErr); ok { //nolint:errorlint // "An Is method should only shallowly compare err and the target and not call Unwrap on either."
+		// However for our purposes here, we will abuse
+		// the Is convention and also consider the addr
+		// and reason fields.
+		return e.addr == err.addr && e.reason == err.reason
+	}
+	return false
+}
+
 func newCtx(log, id string) (_ v2.Context, cancel func()) {
 	ctx, cancel := context.WithCancel(context.Background())
 	return v2.Context{