improvements-2.x-dev/modules/improvements_views/src/Plugin/Field/FieldWidget/ViewsWidget.php

<?php

namespace Drupal\improvements_views\Plugin\Field\FieldWidget;

use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\WidgetBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\views\Views;

/**
 * @FieldWidget(
 *   id = "views_widget",
 *   label = @Translation("Views"),
 *   field_types = {
 *     "views",
 *   },
 * )
 */
class ViewsWidget extends WidgetBase {

  /**
   * {@inheritDoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state): array {
    $element += [
      '#type' => 'select',
      '#options' => Views::getViewsAsOptions(FALSE, 'enabled', NULL, TRUE, TRUE),
      '#default_value' => $items[$delta]->value ?? NULL,
    ];

    return [
      'value' => $element,
    ];
  }

}