collection-8.x-1.x-dev/modules/collection_pathauto/collection_pathauto.module

<?php

use Drupal\Core\Entity\ContentEntityInterface;

/**
 * Implements hook_pathauto_alias_alter().
 *
 * Checks for a canonical collection item and prepends the collection url to the
 * path. It also implements an alter hook so that other modules can further
 * modify the alias.
 */
function collection_pathauto_pathauto_alias_alter(&$alias, array &$context) {
  $collection_content_manager = \Drupal::service('collection.content_manager');
  $path_alias_manager = \Drupal::service('path_alias.manager');

  $entity = reset($context['data']);

  if (empty($entity) || !$entity instanceof ContentEntityInterface) {
    return;
  }

  foreach ($collection_content_manager->getCollectionItemsForEntity($entity) as $collection_item) {
    if ($collection_item->isCanonical()) {
      $collection_url = $path_alias_manager->getAliasByPath('/collection/' . $collection_item->collection->target_id);
      $context['original_alias'] = $alias;
      $alias = $collection_url . $alias;

      // Add relevant collection details to the context and allow other modules to
      // alter the alias.
      $context['collection_item'] = $collection_item;
      $context['canonical_collection'] = $collection_item->collection->entity;
      \Drupal::moduleHandler()->alter('collection_pathauto_alias', $alias, $context);
      break;
    }
  }
}