ForumListingBreadcrumbBuilder::build

public ForumListingBreadcrumbBuilder::build(RouteMatchInterface $route_match)

public function build(RouteMatchInterface $route_match) {
  $breadcrumb = parent::build($route_match);
  $breadcrumb->addCacheContexts(['route']);

  // Add all parent forums to breadcrumbs.
  /** @var \Drupal\Taxonomy\TermInterface $term */
  $term = $route_match->getParameter('taxonomy_term');
  $term_id = $term->id();
  $breadcrumb->addCacheableDependency($term);

  $parents = $this->forumManager->getParents($term_id);
  if ($parents) {
    foreach (array_reverse($parents) as $parent) {
      if ($parent->id() != $term_id) {
        $breadcrumb->addCacheableDependency($parent);
        $breadcrumb->addLink(Link::createFromRoute($parent->label(), 'forum.page', [
          'taxonomy_term' => $parent->id(),
        ]));
      }
    }
  }

  return $breadcrumb;
}