Fix of astarte-platform#232

Fix of issue, now unsetting can be done passing "nil" to appengine devices send-data

Signed-off-by: Eddy Babetto <eddy.babetto@secomind.com>

cmd/appengine/device.go

@@ -1079,14 +1079,25 @@ func devicesSendDataF(command *cobra.Command, args []string) error {
 	}
 
 	var parsedPayloadData interface{}
+
+	fmt.Println(payloadData)
+
 	if err := payloadType.IsValid(); err == nil {
-		if parsedPayloadData, err = parseSendDataPayload(payloadData, payloadType); err != nil {
+
+		if payloadData == "nil" {
+			parsedPayloadData = nil
+		}else{
+			if parsedPayloadData, err = parseSendDataPayload(payloadData, payloadType); err != nil {
 			return err
 		}
+		}
+
+
 	} else {
 		// We have to treat it as an aggregate.
 		aggrPayload := map[string]interface{}{}
 		if err := json.Unmarshal([]byte(payloadData), &aggrPayload); err != nil {
+			fmt.Println("A")
 			return err
 		}
 
@@ -1099,6 +1110,7 @@ func devicesSendDataF(command *cobra.Command, args []string) error {
 			fullPath := fmt.Sprintf("%s/%s", interfacePath, k)
 			mapping, err := interfaces.InterfaceMappingFromPath(iface, fullPath)
 			if err != nil {
+				fmt.Println("B")
 				return err
 			}
 
@@ -1148,8 +1160,16 @@ func devicesSendDataF(command *cobra.Command, args []string) error {
 	var sendDataCall client.AstarteRequest
 
 	if !skipRealmManagementChecks {
-		// We can delegate the entirety of this to astarte-go
-		sendDataCall, err = astarteAPIClient.SendData(realm, deviceID, deviceIdentifierType, iface, interfacePath, parsedPayloadData)
+
+		if parsedPayloadData==nil {
+	// We can delegate the entirety of this to astarte-go
+	sendDataCall, err = astarteAPIClient.UnsetProperty(realm, deviceID, deviceIdentifierType, interfaceName, interfacePath)
+		}else{
+	// We can delegate the entirety of this to astarte-go
+	sendDataCall, err = astarteAPIClient.SendData(realm, deviceID, deviceIdentifierType, iface, interfacePath, parsedPayloadData)
+		}
+
+
 	} else {
 		// Don't risk it. Use raw functions and trust the server to fail, in case.
 		switch interfaceTypeString {