materio-d8/web/modules/custom/materio_user/materio_user.module

<?php

/**
 * @file
 * Contains materio_user.module.
 */

use \Drupal\Core\Form\FormStateInterface;
use \Drupal\Core\Block\BlockPluginInterface;

/**
 * implements hook_form_FORM_ID_alter()
 *
 */
function materio_user_form_user_login_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  // Drupal::logger('materio_user')->notice(print_r($form, true));
  $form['name']['#attributes'] += array(
    "v-model" => "mail",
    "@keyup.enter" => "login"
  );

  $form['pass']['#attributes'] = array(
    "v-model" => "password",
    "@keyup.enter" => "login"
  );

  $form['actions']['submit']['#attributes'] = array(
    "@click.prevent" => "login"
  );

}

/**
 * implements hook_block_view_BASE_BLOCK_ID_alter()
 *
 * https://www.drupal.org/project/drupal/issues/2626224
 */
function materio_user_block_view_user_login_block_alter(array &$build, BlockPluginInterface $block) {
  $build['#pre_render'][] = '_materio_user_user_login_block_pre_render';
}

function _materio_user_user_login_block_pre_render(array $build){
  $user_links = &$build['content']['user_links'];
  $items = &$user_links['#items'];
  // ksm($items);
  $items['create_account']['#url']->mergeOptions(array(
    "attributes" => array(
      "@click.prevent" => "create_account"
    )
  ));
  $items['request_password']['#url']->mergeOptions(array(
    'attributes' => array(
      "@click.prevent" => "request_password"
    )
  ));
  return $build;
}