[MqttValue] Return json content as default value

mqttdevice/mqttdevice.go

@@ -1,6 +1,7 @@
 package mqttdevice
 
 import (
+	"encoding/json"
 	"fmt"
 	"github.com/cyrilix/robocar-base/types"
 	MQTT "github.com/eclipse/paho.mqtt.golang"
@@ -107,9 +108,13 @@ func NewMqttValue(v interface{}) MqttValue {
 	case MqttValue:
 		return val
 	default:
-		log.Printf("invalid mqtt value: %v", val)
+		jsonValue, err := json.Marshal(v)
+		if err != nil {
+			log.Printf("unable to mashall to json value '%v': %v", v, err)
 			return nil
 		}
+		return jsonValue
+	}
 }
 
 func (m *MqttValue) IntValue() (int, error) {

mqttdevice/mqttdevice_test.go

@@ -66,14 +66,14 @@ func TestNewMqttValue(t *testing.T) {
 		{[]byte("test bytes"), []byte("test bytes")},
 
 		{struct {
-			content string
-		}{"invalid"}, nil},
+			Content string
+		}{"other"}, []byte(`{"Content":"other"}`)},
 	}
 
 	for _, c := range cases {
 		val := NewMqttValue(c.value)
 		if string(val) != string(c.expected) {
-			t.Errorf("NewMqttValue(%v): %v, wants %v", c.value, val, c.expected)
+			t.Errorf("NewMqttValue(%v): %v, wants %v", c.value, string(val), string(c.expected))
 		}
 	}
 }