Split validation into multiple methods to simplify login and registration form customizations

[Berdir]

PR for https://www.drupal.org/node/2870783

In my project, I have this now, combined with an alter hook to switch out the class:

/**
 * Customized Login pane that allows registration by e-mail.
 */
class EmailLoginPane extends Login {

  /**
   * {@inheritdoc}
   */
  public function buildPaneForm(array $pane_form, FormStateInterface $form_state, array &$complete_form) {
    $pane_form = parent::buildPaneForm($pane_form, $form_state, $complete_form);
    $pane_form['returning_customer']['name']['#title'] = $this->t('E-mail or username');
    $pane_form['register']['name']['#access'] = FALSE;
    return $pane_form;
  }

  /**
   * {@inheritdoc}
   */
  protected function getAndValidateRegisterUserValues(array &$pane_form, FormStateInterface $form_state) {
    if ($user_values = parent::getAndValidateRegisterUserValues($pane_form, $form_state)) {
      $user_values['name'] = $user_values['mail'];
      return $user_values;
    }
  }

}

Not sure yet about spliting up the login method further.

[bojanz]

It's odd that we have a validateRegister() method that does no validation, the entire logic is in the oddly named getAndValidateRegisterUserValues, which is only used in one place. What's the reasoning behind that split?

[Berdir]

Yeah, the names are bad, suggestions welcome. The reason for the split is being able to change the user values, see my example. For that to work there needs to be a way to do something between bulding the values array and creating the entity. Another approach would be an "alter" method between or/and an event.