Exclude entities which have a redirect from the search api index

For a custom project, we use a taxonomy to tag nodes. Some terms have their own page, while others redirect to a node. The search on the site has one index which contains both nodes and terms, but the terms which are redirecting shouldn't show up when viewing a search results page. While it's possible to use hook_search_api_index_items_alter(), a nicer way to exclude them is by using a processor plugin so you can enable them in the UI per index. The relevant code is underneath. Adjust to your own likings - and maybe inject the service if you want to as well :)

<?php
namespace Drupal\project\Plugin\search_api\processor;

use
Drupal\search_api\IndexInterface;
use
Drupal\search_api\Processor\ProcessorPluginBase;

/**
 * Excludes entities which have a redirect.
 *
 * @SearchApiProcessor(
 *   id = "entity_redirect",
 *   label = @Translation("Entity redirect"),
 *   description = @Translation("Exclude entities which have a redirect from being indexed."),
 *   stages = {
 *     "alter_items" = 0,
 *   },
 * )
 */
class EntityRedirect extends ProcessorPluginBase {

 
/**
   * {@inheritdoc}
   */
 
public static function supportsIndex(IndexInterface $index) {
    foreach (
$index->getDatasources() as $datasource) {
     
$entity_type_id = $datasource->getEntityTypeId();
      if (!
$entity_type_id) {
        continue;
      }
      if (
$entity_type_id === 'node' || $entity_type_id == 'taxonomy_term') {
        return
TRUE;
      }
    }
    return
FALSE;
  }

 
/**
   * {@inheritdoc}
   */
 
public function alterIndexedItems(array &$items) {
   
$repository = \Drupal::service('redirect.repository');
   
$pathAliasmanager = \Drupal::service('path.alias_manager');
   
/** @var \Drupal\search_api\Item\ItemInterface $item */
   
foreach ($items as $item_id => $item) {
     
$object = $item->getOriginalObject()->getValue();
      try {
       
$path = $object->toUrl()->toString();
       
$path = $pathAliasmanager->getPathByAlias($path);
       
$path = ltrim($path, '/');
       
$redirect = $repository->findMatchingRedirect($path);
        if (!empty(
$redirect)) {
          unset(
$items[$item_id]);
        }
      }
      catch (
\Exception $ignored) {}
    }
  }

}
?>
Exclude entities which have a redirect from the search api index: https://realize.be/blog/exclude-entities-which-have-redirect-search-api-index