Node with multiple taxonomies - can I pass value as URL param

You can implement hook_breadcrumb_alter to modify with custom code here's an example from a contrib module:

https://git.drupalcode.org/project/dynamic_breadcrumb/-/blob/master/dyna...

You can also try the substitute feature. In general, the breadcrumb matches the path. There is a setting to display taxonomy added to crumbs, I just don't know how it chooses which one to use when there are multiple.

Hey Greg, thanks for the tip around the custom code. I ended up using the new BreadcrumbBuilderInterface approach - and pulling the taxonomy ID either from the URL - or the first entry in the list of taxonomies I have on the product. Works a treat - thanks for the hint!

Awesome! If you can, it would be awesome if you could post your alter hook as an example for future folks before we close this.

~G

I can add it to the documentation.

Entry in services.yml

  neway_lintels.breadcrumb:
    class: Drupal\neway_lintels\BreadcrumbBuilder
    arguments: [ '@entity_type.manager', '@entity.repository' ]
    tags:
      - { name: breadcrumb_builder, priority: 1004 }

<?php
namespace Drupal\neway_lintels;

use Drupal;
use Drupal\commerce_product\Entity\Product;
use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
use Drupal\Core\Entity\EntityRepositoryInterface;
use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\Core\Link;
use Drupal\Core\Routing\LinkGeneratorTrait;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\StringTranslation\StringTranslationTrait;

class BreadcrumbBuilder implements BreadcrumbBuilderInterface {

  use StringTranslationTrait;

  public function __construct(EntityTypeManagerInterface $entity_type_manager, EntityRepositoryInterface $entity_repository) {

    $this->entityTypeManager = $entity_type_manager;
    $this->entityRepository = $entity_repository;

  }

  /**
   * By advent of there being a breadcrumb_builder name in the services.yml file - the Symphony framework runs
   * the below - to see if it is applicable - if it is - the bigger weight wins
   * 
   * Code by Wayne Foster, Neway Technology Ltd, UK
   * 
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match): bool {
    $allowedRoutes = [
      "entity.commerce_product.canonical",
    ];
    $routeName = $route_match->getRouteName();
    //dump("bread applies termID: " . $termID . ", routeName:" . $routeName);
    return (in_array($routeName, $allowedRoutes));
  }

  /**
   * {@inheritdoc}
   */
  public function build(RouteMatchInterface $route_match): Breadcrumb {
    $breadcrumb = new Breadcrumb();
    /** @var Product $entityProduct */
    $entityProduct = $route_match->getParameter('commerce_product');
    $termID = Drupal::request()->get('term');
    /** @var \Drupal\taxonomy\TermStorageInterface $parents */
    $parents;

    // We have found a term ID on the URL - use it
    if ($termID && $termID > 0) {
      $parents = $this->entityTypeManager->getStorage('taxonomy_term')
        ->loadAllParents($termID);
    } // if not - then get the first entry on the product category list of taxonomies
    else {
      $taxonomy_field_name = 'product_category';
      /** @var  \Drupal\taxonomy\Entity\Term $productCategory */
      $productCategory = $entityProduct->$taxonomy_field_name->entity;
      //dump("firstCategory", $productCategory);
      $parents = $this->entityTypeManager->getStorage('taxonomy_term')
        ->loadAllParents($productCategory->id());
    }

    // Add a home page link to the start of the breadcrumb render array
    $links[] = Link::createFromRoute(t("Home"), '<front>');
    $linksTax = [];
    // iterate up the taxonomy parents
    foreach ($parents as $parent) {
      $parent = $this->entityRepository->getTranslationFromContext($parent);
      $linksTax[] = $parent->toLink();
    }
    $links = array_merge($links, array_reverse($linksTax));
    $links[] = Link::createFromRoute($entityProduct->getTitle(), '<none>');
    $breadcrumb->setLinks($links);
    $breadcrumb->addCacheContexts(['route', 'url.path','url.query_args']);

    return $breadcrumb;
  }

}

Interesting approach to run a new builder restricted only for a certain path to selectively apply options. If you had used the taxonomy option in Easy Breadcrumb, it would apply to every route on the site instead of selectively to your commerce products. Super cool.

Might be worth to turn this into a Documentation Page