Fix: Return an error when fail to enqueue

The functions that enqueue messages didn't had a return for the
handler, with this the error was only logged instead of returned which
may cause the user to have an ID for a message that was not published.

mqtt_client.c

@@ -1004,7 +1004,7 @@ static bool is_valid_mqtt_msg(esp_mqtt_client_handle_t client, int msg_type, int
     return false;
 }
 
-static void mqtt_enqueue_oversized(esp_mqtt_client_handle_t client, uint8_t *remaining_data, int remaining_len)
+static outbox_item_handle_t mqtt_enqueue_oversized(esp_mqtt_client_handle_t client, uint8_t *remaining_data, int remaining_len)
 {
     ESP_LOGD(TAG, "mqtt_enqueue_oversized id: %d, type=%d successful",
              client->mqtt_state.pending_msg_id, client->mqtt_state.pending_msg_type);
@@ -1018,16 +1018,14 @@ static void mqtt_enqueue_oversized(esp_mqtt_client_handle_t client, uint8_t *rem
     msg.remaining_data = remaining_data;
     msg.remaining_len = remaining_len;
     //Copy to queue buffer
-    outbox_enqueue(client->outbox, &msg, platform_tick_get_ms());
+    return outbox_enqueue(client->outbox, &msg, platform_tick_get_ms());
-
     //unlock
 }
 
-static void mqtt_enqueue(esp_mqtt_client_handle_t client)
+static outbox_item_handle_t mqtt_enqueue(esp_mqtt_client_handle_t client)
 {
     ESP_LOGD(TAG, "mqtt_enqueue id: %d, type=%d successful",
              client->mqtt_state.pending_msg_id, client->mqtt_state.pending_msg_type);
-    //lock mutex
     if (client->mqtt_state.pending_msg_count > 0) {
         outbox_message_t msg = { 0 };
         msg.data = client->mqtt_state.outbound_message->data;
@@ -1036,9 +1034,9 @@ static void mqtt_enqueue(esp_mqtt_client_handle_t client)
         msg.msg_type = client->mqtt_state.pending_msg_type;
         msg.msg_qos = client->mqtt_state.pending_publish_qos;
         //Copy to queue buffer
-        outbox_enqueue(client->outbox, &msg, platform_tick_get_ms());
+        return outbox_enqueue(client->outbox, &msg, platform_tick_get_ms());
     }
-    //unlock
+    return NULL;
 }
 
 
@@ -1635,8 +1633,12 @@ int esp_mqtt_client_subscribe(esp_mqtt_client_handle_t client, const char *topic
 
     client->mqtt_state.pending_msg_type = mqtt_get_type(client->mqtt_state.outbound_message->data);
     client->mqtt_state.pending_msg_count ++;
-    mqtt_enqueue(client); //move pending msg to outbox (if have)
+    //move pending msg to outbox (if have)
-    outbox_set_pending(client->outbox, client->mqtt_state.pending_msg_id, TRANSMITTED);
+    if (!mqtt_enqueue(client)) {
+        MQTT_API_UNLOCK(client);
+        return -1;
+    }
+    outbox_set_pending(client->outbox, client->mqtt_state.pending_msg_id, TRANSMITTED);// handle error
 
     if (mqtt_write_data(client) != ESP_OK) {
         ESP_LOGE(TAG, "Error to subscribe topic=%s, qos=%d", topic, qos);
@@ -1673,8 +1675,11 @@ int esp_mqtt_client_unsubscribe(esp_mqtt_client_handle_t client, const char *top
 
     client->mqtt_state.pending_msg_type = mqtt_get_type(client->mqtt_state.outbound_message->data);
     client->mqtt_state.pending_msg_count ++;
-    mqtt_enqueue(client);
+    if (!mqtt_enqueue(client)) {
-    outbox_set_pending(client->outbox, client->mqtt_state.pending_msg_id, TRANSMITTED);
+        MQTT_API_UNLOCK(client);
+        return -1;
+    }
+    outbox_set_pending(client->outbox, client->mqtt_state.pending_msg_id, TRANSMITTED); //handle error
 
     if (mqtt_write_data(client) != ESP_OK) {
         ESP_LOGE(TAG, "Error to unsubscribe topic=%s", topic);
@@ -1719,10 +1724,14 @@ static inline int mqtt_client_enqueue_priv(esp_mqtt_client_handle_t client, cons
         client->mqtt_state.pending_msg_count ++;
         // by default store as QUEUED (not transmitted yet) only for messages which would fit outbound buffer
         if (client->mqtt_state.mqtt_connection.message.fragmented_msg_total_length == 0) {
-            mqtt_enqueue(client);
+            if (!mqtt_enqueue(client)) {
+                return -1;
+            }
         } else {
             int first_fragment = client->mqtt_state.outbound_message->length - client->mqtt_state.outbound_message->fragmented_msg_data_offset;
-            mqtt_enqueue_oversized(client, ((uint8_t *)data) + first_fragment, len - first_fragment);
+            if (!mqtt_enqueue_oversized(client, ((uint8_t *)data) + first_fragment, len - first_fragment)) {
+                return -1;
+            }
             client->mqtt_state.outbound_message->fragmented_msg_total_length = 0;
         }
     }