Drupal 8: Custom breadcrumbs for node with hierarchical taxonomy term reference

breadcrumb.services.yml

services:
 breadcrumb.breadcrumb:
   class: Drupal\breadcrumb\BreadcrumbBuilder
   tags:
    - { name: breadcrumb_builder, priority: 10001 }
   arguments: ['@router.request_context', '@access_manager', '@router.no_access_checks', '@path_processor_manager', '@config.factory', '@title_resolver', '@current_user', '@path.current']

BreadcrumbBuilder.php

<?php

namespace Drupal\breadcrumb;


use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
use Drupal\Core\Link;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Url;
use Drupal\system\PathBasedBreadcrumbBuilder;

/**
 * Build custom breadcrumb for Product node pages.
 *
 * Adds links to referenced taxonomy terms (product categories)
 * include all nested terms in pattern:
 *
 * Home->Category view->Category1->Category1.2->Category1.2.3
 *
 * Strings usage:
 * 'view.vyrobni_program.page_1' = route to view for breadcrumb level 2.
 * 'Výrobní program' = title for breadcrumb level 2.
 * 'field_product_category' = field name in node with reference to term.
 * 'produkt' = Content type (node bundle) machine name for Products.
 *
 * Class BreadcrumbBuilder
 *
 * @package Drupal\breadcrumb
 */
class BreadcrumbBuilder extends PathBasedBreadcrumbBuilder implements BreadcrumbBuilderInterface {

  /**
   * @var \Drupal\Core\Breadcrumb\Breadcrumb
   */
  protected $breadcrumb;

  /**
   * Apply breadcrumb only on node type "product".
   *
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match) {
    $node = $route_match->getParameter('node');
    if ($node) {
      $node_type = $node->bundle();
      if ($node_type == 'produkt') {
        return TRUE;
      }
    }
    return FALSE;
  }

  /**
   * Builds the breadcrumb.
   *
   * {@inheritdoc}
   */
  public function build(RouteMatchInterface $route_match) {
    $this->breadcrumb = new Breadcrumb();
    // Home - 1st level.
    $this->breadcrumb->addLink(Link::createFromRoute('Home', '<front>'));
    // Product view - 2nd level.
    $this->breadcrumb->addLink(Link::createFromRoute('Výrobní program', 'view.vyrobni_program.page_1'));

    // Get node and referenced term.
    $node = $route_match->getParameter('node');
    /** @var \Drupal\taxonomy\Entity\Term $categoryTerm */
    $categoryTerm = $node->get('field_product_category')->entity;

    // 3rd...n-th level: Add links to all parents.
    $this->addTermChainLink($categoryTerm);

    $this->breadcrumb->addCacheContexts(['route']);
    return $this->breadcrumb;
  }

  /**
   * Get parent taxonomy term.
   *
   * @param \Drupal\taxonomy\Entity\Term $term
   *   Taxonomy Term Entity.
   *
   * @return \Drupal\taxonomy\TermInterface|bool
   *   False if no parent.
   */
  protected function getParentTerm($term) {
    /** @var \Drupal\taxonomy\TermStorageInterface $termStorage */
    $termStorage = \Drupal::entityTypeManager()->getStorage('taxonomy_term');
    $termParents = $termStorage->loadParents($term->id());
    if ($termParents) {
      $termParent = reset($termParents);
      return $termParent;
    }
    return FALSE;
  }

  /**
   * @param \Drupal\taxonomy\Entity\Term $term
   */
  protected function addTermChainLink($term) {
    // Look for a parent of this term
    /** @var \Drupal\taxonomy\Entity\Term $parentTerm */
    if ($parentTerm = $this->getParentTerm($term)) {
      // Recursive call this method for the parent.
      $this->addTermChainLink($parentTerm);
    };
    /** @var Url $termUrl */
    $this->addLinkToTerm($term);
  }

  /**
   * @param \Drupal\taxonomy\Entity\Term $term
   */
  protected function addLinkToTerm($term) {
    /** @var Url $termUrl */
    $termUrl = $term->toUrl();
    $this->breadcrumb->addLink(Link::fromTextAndUrl($term->label(), $termUrl));
  }
}

miss spelling its product