libnm-core: don't serialize empty address-labels

If no address in an NMSettingIP4Config has a label, then don't bother
serializing an array of empty strings.

libnm-core/nm-setting-ip4-config.c

@@ -304,16 +304,29 @@ ip4_address_labels_get (NMSetting    *setting,
                         const char   *property)
 {
 	NMSettingIPConfig *s_ip = NM_SETTING_IP_CONFIG (setting);
+	gboolean have_labels = FALSE;
 	GPtrArray *labels;
 	GVariant *ret;
 	int num_addrs, i;
 
-	labels = g_ptr_array_new ();
 	num_addrs = nm_setting_ip_config_get_num_addresses (s_ip);
 	for (i = 0; i < num_addrs; i++) {
 		NMIPAddress *addr = nm_setting_ip_config_get_address (s_ip, i);
 		GVariant *label = nm_ip_address_get_attribute (addr, "label");
 
+		if (label) {
+			have_labels = TRUE;
+			break;
+		}
+	}
+	if (!have_labels)
+		return NULL;
+
+	labels = g_ptr_array_sized_new (num_addrs);
+	for (i = 0; i < num_addrs; i++) {
+		NMIPAddress *addr = nm_setting_ip_config_get_address (s_ip, i);
+		GVariant *label = nm_ip_address_get_attribute (addr, "label");
+
 		g_ptr_array_add (labels, (char *) (label ? g_variant_get_string (label, NULL) : ""));
 	}
 

libnm-core/tests/test-general.c

@@ -350,6 +350,25 @@ test_setting_ip4_config_labels (void)
 	label = nm_ip_address_get_attribute (addr, "label");
 	g_assert (label == NULL);
 
+	/* The 'address-labels' property should be omitted from the serialization if
+	 * there are no non-NULL labels.
+	 */
+	conn = nmtst_create_minimal_connection ("label test", NULL, NM_SETTING_WIRED_SETTING_NAME, NULL);
+	nm_connection_add_setting (conn, nm_setting_duplicate (NM_SETTING (s_ip4)));
+	dict = nm_connection_to_dbus (conn, NM_CONNECTION_SERIALIZE_ALL);
+	g_object_unref (conn);
+
+	setting_dict = g_variant_lookup_value (dict, NM_SETTING_IP4_CONFIG_SETTING_NAME, NM_VARIANT_TYPE_SETTING);
+	g_assert (setting_dict != NULL);
+
+	value = g_variant_lookup_value (setting_dict, "address-labels", NULL);
+	g_assert (value == NULL);
+
+	g_variant_unref (setting_dict);
+	g_variant_unref (dict);
+
+	/* Now back to constructing the original s_ip4... */
+
 	/* addr 2 */
 	addr = nm_ip_address_new (AF_INET, "2.2.2.2", 24, &error);
 	g_assert_no_error (error);