class ShortcutForm

class ShortcutForm extends ContentEntityForm {
    
    /**
     * The entity being used by this form.
     *
     * @var \Drupal\shortcut\ShortcutInterface
     */
    protected $entity;
    
    /**
     * {@inheritdoc}
     */
    public function form(array $form, FormStateInterface $form_state) {
        $form = parent::form($form, $form_state);
        $form['#attached']['library'][] = 'core/drupal.form';
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function save(array $form, FormStateInterface $form_state) {
        $entity = $this->entity;
        $status = $entity->save();
        $url = $entity->getUrl();
        // There's an edge case where a user can have permission to
        // 'link to any content', but has no right to access the linked page. So we
        // check the access before showing the link.
        if ($url->access()) {
            $view_link = Link::fromTextAndUrl($entity->getTitle(), $url)
                ->toString();
        }
        else {
            $view_link = $entity->getTitle();
        }
        if ($status == SAVED_UPDATED) {
            $message = $this->t('The shortcut %link has been updated.', [
                '%link' => $view_link,
            ]);
        }
        else {
            $message = $this->t('Added a shortcut for %title.', [
                '%title' => $view_link,
            ]);
        }
        $this->messenger()
            ->addStatus($message);
        $form_state->setRedirect('entity.shortcut_set.customize_form', [
            'shortcut_set' => $entity->bundle(),
        ]);
    }

}