class UserName

class UserName extends User {
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        $entity_type = $this->entityTypeManager
            ->getDefinition('user');
        $form['multiple']['#options'] = [
            0 => $this->t('Single name', [
                '%type' => $entity_type->getLabel(),
            ]),
            1 => $this->t('One or more names separated by , or +', [
                '%type' => $entity_type->getLabel(),
            ]),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateArgument($argument) {
        if ($this->multipleCapable && $this->options['multiple']) {
            // At this point only interested in individual IDs no matter what type,
            // just splitting by the allowed delimiters.
            $names = array_filter(preg_split('/[,+ ]/', $argument));
        }
        elseif ($argument) {
            $names = [
                $argument,
            ];
        }
        else {
            return FALSE;
        }
        $accounts = $this->userStorage
            ->loadByProperties([
            'name' => $names,
        ]);
        // If there are no accounts, return FALSE now. As we will not enter the
        // loop below otherwise.
        if (empty($accounts)) {
            return FALSE;
        }
        // Validate each account. If any fails break out and return false.
        foreach ($accounts as $account) {
            if (!in_array($account->getAccountName(), $names) || !$this->validateEntity($account)) {
                return FALSE;
            }
        }
        return TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function processSummaryArguments(&$args) {
        // If the validation says the input is a username, we should reverse the
        // argument so it works for example for generation summary URLs.
        $uids_arg_keys = array_flip($args);
        foreach ($this->userStorage
            ->loadMultiple($args) as $uid => $account) {
            $args[$uids_arg_keys[$uid]] = $account->label();
        }
    }

}