Migration::saveQueuedMessages() is not called for records that are skipped via prepareRow()

In #1421974: Allow messages to be saved in prepareRow() the queue message options was added, but as far I can tell this doesn't work for rows skipped via prepareRow(). I think that inside MigrateSource::prepareRow() we need to clean the existing messages (wipe old messages) and save the queued ones before setting currentRow and currentKey to NULL.

Right now the queued message are saved inside Migration::import(), but skipped records don't go that far into processing (they are skipped inside MigrationSource::next() function).

This is the code I have inside MyMigration::prepareRow() and doesn't work. The messages are saved after a valid row is found with the id of the valid row.

  function prepareRow() {
    // ...
    if (!$this->hasAllMandatoryFields()) {
      $this->queueMessage(t('Row skipped because is missing essential information'), MigrationBase::MESSAGE_INFORMATIONAL);
      return FALSE;
    }
    // ...
  }

Right now I fixed by adding changing Migration::saveQueuedMessages():

  /**
   * Save any messages we've queued up to the message table.
   *
   * @param $wipe
   *   Boolean value indicating if the old messages should be wiped before save.
   */
  public function saveQueuedMessages($wipe = FALSE) {
    if ($wipe) {
      $this->map->delete($this->currentSourceKey(), TRUE);
    }

    foreach ($this->queuedMessages as $queued_message) {
      $this->saveMessage($queued_message['message'], $queued_message['level']);
    }
    $this->queuedMessages = array();
  }

And calling it inside MigrationSource::prepareRow():

  /**
   * Give the calling migration a shot at manipulating, and possibly rejecting,
   * the source row.
   *
   * @return bool
   *  FALSE if the row is to be skipped.
   */
  protected function prepareRow($row) {
    migrate_instrument_start(get_class($this->activeMigration) . ' prepareRow');
    $return = $this->activeMigration->prepareRow($row);
    migrate_instrument_stop(get_class($this->activeMigration) . ' prepareRow');
    // We're explicitly skipping this row - keep track in the map table
    if ($return === FALSE) {
      $this->activeMigration->getMap()->saveIDMapping($row, array(),
        MigrateMap::STATUS_IGNORED, $this->activeMigration->rollbackAction);
      $this->activeMigration->saveQueuedMessages(TRUE); // Save queued messages
      $this->numIgnored++;
      $this->currentRow = NULL;
      $this->currentKey = NULL;
    }
    else {
      $return = TRUE;
    }
    $this->numProcessed++;
    return $return;
  }