ignore unknown monitor type in FindMonitors

monitors.go

@@ -325,7 +325,12 @@ func (c *Client) FindMonitors() ([]Monitor, error) {
 	for _, rawmes := range data.Monitors {
 		m, err := decodeMonitor(rawmes)
 		if err != nil {
-			return nil, err
+			switch err.(type) {
+			case *unknownMonitorTypeError:
+				break
+			default:
+				return nil, err
+			}
 		}
 		ms = append(ms, m)
 	}
@@ -397,6 +402,14 @@ func (c *Client) DeleteMonitor(monitorID string) (Monitor, error) {
 	return decodeMonitorReader(resp.Body)
 }
 
+type unknownMonitorTypeError struct {
+	Type string
+}
+
+func (e *unknownMonitorTypeError) Error() string {
+	return fmt.Sprintf("unknown monitor type: %s", e.Type)
+}
+
 // decodeMonitor decodes json.RawMessage and returns monitor.
 func decodeMonitor(mes json.RawMessage) (Monitor, error) {
 	var typeData struct {
@@ -419,6 +432,8 @@ func decodeMonitor(mes json.RawMessage) (Monitor, error) {
 		m = &MonitorExpression{}
 	case monitorTypeAnomalyDetection:
 		m = &MonitorAnomalyDetection{}
+	default:
+		return nil, &unknownMonitorTypeError{Type: typeData.Type}
 	}
 	if err := json.Unmarshal(mes, m); err != nil {
 		return nil, err

monitors_test.go

@@ -661,6 +661,27 @@ func TestDecodeEncodeMonitor(t *testing.T) {
 	}
 }
 
+func TestDecodeUnknownMonitor(t *testing.T) {
+	json := `{
+		"id"  : "2cSZzK3XfmE",
+		"type": "unknown",
+		"unknownField": "unknownValue"
+	}`
+	gotMonitor, err := decodeMonitorReader(strings.NewReader(json))
+	if gotMonitor != nil {
+		t.Errorf("gotMonitor should be nil but: %v", gotMonitor)
+	}
+	if err == nil {
+		t.Errorf("err should be unknownMonitorTypeError but: %v", err)
+	} else {
+		switch err.(type) {
+		case *unknownMonitorTypeError:
+		default:
+			t.Errorf("err should be unknownMonitorTypeError but: %v", err)
+		}
+	}
+}
+
 func equalJSON(x, y string) bool {
 	var xval, yval interface{}
 	json.Unmarshal([]byte(x), &xval) //nolint