class ViewsMenuLinkForm

class ViewsMenuLinkForm extends MenuLinkDefaultForm {
    
    /**
     * The edited views menu link.
     *
     * @var \Drupal\views\Plugin\Menu\ViewsMenuLink
     */
    protected $menuLink;
    
    /**
     * {@inheritdoc}
     */
    public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
        // Put the title field first.
        $form['title'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Title'),
            // @todo Ensure that the view is not loaded with a localized title.
            //   https://www.drupal.org/node/2309507
'#default_value' => $this->menuLink
                ->getTitle(),
            '#weight' => -10,
        ];
        $form['description'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Description'),
            '#description' => $this->t('Shown when hovering over the menu link.'),
            // @todo Ensure that the view is not loaded with a localized description.
            //   https://www.drupal.org/node/2309507
'#default_value' => $this->menuLink
                ->getDescription(),
            '#weight' => -5,
        ];
        $form += parent::buildConfigurationForm($form, $form_state);
        $form['info']['#weight'] = -8;
        $form['path']['#weight'] = -7;
        $view = $this->menuLink
            ->loadView();
        $id = $view->storage
            ->id();
        $label = $view->storage
            ->label();
        if ($this->moduleHandler
            ->moduleExists('views_ui')) {
            $message = $this->t('This link is provided by the Views module. The path can be changed by editing the view <a href=":url">@label</a>', [
                ':url' => Url::fromRoute('entity.view.edit_form', [
                    'view' => $id,
                ])->toString(),
                '@label' => $label,
            ]);
        }
        else {
            $message = $this->t('This link is provided by the Views module from view %label.', [
                '%label' => $label,
            ]);
        }
        $form['info']['#title'] = $message;
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function extractFormValues(array &$form, FormStateInterface $form_state) {
        $definition = parent::extractFormValues($form, $form_state);
        $definition['title'] = $form_state->getValue('title');
        $definition['description'] = $form_state->getValue('description');
        return $definition;
    }

}