ForumNodeBreadcrumbBuilder.php

<?php

namespace Drupal\forum\Breadcrumb;

use Drupal\Core\Link;
use Drupal\Core\Routing\RouteMatchInterface;

/**
 * Breadcrumb builder for forum nodes.
 */
class ForumNodeBreadcrumbBuilder extends ForumBreadcrumbBuilderBase {
    
    /**
     * {@inheritdoc}
     */
    public function applies(RouteMatchInterface $route_match) {
        return $route_match->getRouteName() == 'entity.node.canonical' && $route_match->getParameter('node') && $this->forumManager
            ->checkNodeType($route_match->getParameter('node'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function build(RouteMatchInterface $route_match) {
        $breadcrumb = parent::build($route_match);
        $breadcrumb->addCacheContexts([
            'route',
        ]);
        $parents = $this->termStorage
            ->loadAllParents($route_match->getParameter('node')->forum_tid);
        if ($parents) {
            $parents = array_reverse($parents);
            foreach ($parents as $parent) {
                $breadcrumb->addCacheableDependency($parent);
                $breadcrumb->addLink(Link::createFromRoute($parent->label(), 'forum.page', [
                    'taxonomy_term' => $parent->id(),
                ]));
            }
        }
        return $breadcrumb;
    }

}