class MenuLinkEditForm

class MenuLinkEditForm extends FormBase {
    
    /**
     * The class resolver.
     *
     * @var \Drupal\Core\DependencyInjection\ClassResolverInterface
     */
    protected $classResolver;
    
    /**
     * Constructs a MenuLinkEditForm object.
     *
     * @param \Drupal\Core\DependencyInjection\ClassResolverInterface $class_resolver
     *   The class resolver.
     */
    public function __construct(ClassResolverInterface $class_resolver) {
        $this->classResolver = $class_resolver;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('class_resolver'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'menu_link_edit';
    }
    
    /**
     * {@inheritdoc}
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     * @param \Drupal\Core\Menu\MenuLinkInterface $menu_link_plugin
     *   The plugin instance to use for this form.
     */
    public function buildForm(array $form, FormStateInterface $form_state, MenuLinkInterface $menu_link_plugin = NULL) {
        $form['menu_link_id'] = [
            '#type' => 'value',
            '#value' => $menu_link_plugin->getPluginId(),
        ];
        $class_name = $menu_link_plugin->getFormClass();
        $form['#plugin_form'] = $this->classResolver
            ->getInstanceFromDefinition($class_name);
        $form['#plugin_form']->setMenuLinkInstance($menu_link_plugin);
        $form += $form['#plugin_form']->buildConfigurationForm($form, $form_state);
        $form['actions'] = [
            '#type' => 'actions',
        ];
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Save'),
            '#button_type' => 'primary',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        $form['#plugin_form']->validateConfigurationForm($form, $form_state);
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $link = $form['#plugin_form']->submitConfigurationForm($form, $form_state);
        $this->messenger()
            ->addStatus($this->t('The menu link has been saved.'));
        $form_state->setRedirect('entity.menu.edit_form', [
            'menu' => $link->getMenuName(),
        ]);
    }

}