Drupal\contextual\Plugin\views\field\ContextualLinks.php

<?php

namespace Drupal\contextual\Plugin\views\field;

use Drupal\Component\Serialization\Json;
use Drupal\Component\Utility\Html;
use Drupal\Component\Utility\UrlHelper;
use Drupal\Core\Routing\RedirectDestinationTrait;
use Drupal\Core\Url;
use Drupal\views\Plugin\views\field\Links;
use Drupal\views\ResultRow;

/**
 * Provides a handler that adds contextual links.
 *
 * @ingroup views_field_handlers
 *
 * @ViewsField("contextual_links")
 */
class ContextualLinks extends Links {

  /**
   * {@inheritdoc}
   */
  public function preRender(&$values) {
    // Add a row plugin css class for the contextual link.
    $class = 'contextual-region';
    if (!empty($this->view->style_plugin->options['row_class'])) {
      $this->view->style_plugin->options['row_class'] .= " $class";
    }
    else {
      $this->view->style_plugin->options['row_class'] = $class;
    }
  }

  /**
   * Overrides \Drupal\views\Plugin\views\field\FieldPluginBase::render().
   *
   * Renders the contextual fields.
   *
   * @param \Drupal\views\ResultRow $values
   *   The values retrieved from a single row of a view's query result.
   *
   * @see contextual_preprocess()
   * @see contextual_contextual_links_view_alter()
   */
  public function render(ResultRow $values) {
    $build = [];
    $links = $this->getLinks();

    $key = 'view.' . $this->view->id() . '.' . $this->view->getDisplay()->getPluginId() . '.' . $values->index;
    foreach ($links as $i => $link) {
      $build['#contextual_links'][$key . '.' . $i]['route_parameters'] = $link['url']->getRouteParameters();
    }

    return $build;
  }

}