NavigationMenuLinkTree.php

<?php

declare (strict_types=1);
namespace Drupal\navigation\Menu;

use Drupal\Core\Menu\MenuLinkTree;

/**
 * Extends MenuLinkTree to add specific theme suggestions for the navigation.
 *
 * @internal
 */
final class NavigationMenuLinkTree extends MenuLinkTree {
    
    /**
     * {@inheritdoc}
     */
    public function build(array $tree) : array {
        if (!$tree) {
            return [];
        }
        $build = parent::build($tree);
        if (empty($build['#items'])) {
            return [];
        }
        
        /** @var \Drupal\Core\Menu\MenuLinkInterface $link */
        $first_link = reset($tree)->link;
        // Get the menu name of the first link.
        $menu_name = $first_link->getMenuName();
        // Add a more specific theme suggestion to differentiate this rendered
        // menu from others.
        $build['#menu_name'] = $menu_name;
        $build['#theme'] = 'navigation_menu__' . strtr($menu_name, '-', '_');
        // Loop through menu items and add the plugin id as a class.
        foreach ($tree as $item) {
            if ($item->access
                ->isAllowed()) {
                $plugin_id = $item->link
                    ->getPluginId();
                $plugin_class = str_replace('.', '_', $plugin_id);
                $build['#items'][$plugin_id]['class'] = $plugin_class;
            }
        }
        return $build;
    }

}