BlockForm::validateForm

public BlockForm::validateForm(array &$form, FormStateInterface $form_state)

public function validateForm(array &$form, FormStateInterface $form_state) {
  parent::validateForm($form, $form_state);

  $form_state->setValue('weight', (int) $form_state->getValue('weight'));
  // The Block Entity form puts all block plugin form elements in the
  // settings form element, so just pass that to the block for validation.
  $this->getPluginForm($this->entity->getPlugin())->validateConfigurationForm($form['settings'], SubformState::createForSubform($form['settings'], $form, $form_state));
  $this->validateVisibility($form, $form_state);
}