Make TermWeightWidgetOrderProcessor respect the full hierarchy.

Uses all the ancestors of each term to create the full materialized path of the hierarchy, to be used in sorting.

src/Plugin/facets/processor/TermWeightWidgetOrderProcessor.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\facets\Plugin\facets\processor;
 
+use Drupal\Component\Utility\Number;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\UnchangingCacheableDependencyTrait;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
@@ -36,6 +37,13 @@ class TermWeightWidgetOrderProcessor extends SortProcessorPluginBase implements
    */
   protected $entityTypeManager;
 
+  /**
+   * The alpha-decimal representation of the taxonomy hierarchy in a flat array.
+   *
+   * @var array
+   */
+  protected array $hierarchy;
+
   /**
    * Constructs a new object.
    *
@@ -70,39 +78,27 @@ class TermWeightWidgetOrderProcessor extends SortProcessorPluginBase implements
    * {@inheritdoc}
    */
   public function sortResults(Result $a, Result $b) {
-    // Get the term weight once.
-    if ($a->get('termWeight') === NULL || $b->get('termWeight') === NULL) {
-      $ids = [];
-      if ($a->get('termWeight') === NULL) {
-        $a_raw = $a->getRawValue();
-        $ids[] = $a_raw;
+    /** @var \Drupal\taxonomy\TermStorageInterface $term_storage */
+    $term_storage = $this->entityTypeManager->getStorage('taxonomy_term');
+    foreach ([$a->getRawValue(), $b->getRawValue()] as $term_id) {
+      if (isset($this->hierarchy[$term_id])) {
+        continue;
       }
-      if ($b->get('termWeight') === NULL) {
-        $b_raw = $b->getRawValue();
-        $ids[] = $b_raw;
-      }
-      $entities = $this->entityTypeManager
-        ->getStorage('taxonomy_term')
-        ->loadMultiple($ids);
-      if ($a->get('termWeight') === NULL) {
-        if (empty($entities[$a_raw])) {
-          return 0;
-        }
-        $a->set('termWeight', $entities[$a_raw]->getWeight());
-      }
-      if ($b->get('termWeight') === NULL) {
-        if (empty($entities[$b_raw])) {
-          return 0;
-        }
-        $b->set('termWeight', $entities[$b_raw]->getWeight());
+      // Ancestors include the term itself.
+      $ancestors = $term_storage->loadAllParents($term_id);
+      // Reverse the order of the ancestors so that the root term is first.
+      $ancestors = \array_reverse($ancestors);
+
+      $materialised_weight = '';
+      foreach ($ancestors as $ancestor) {
+        // Build an alpha-decimal representation of the term's weight,
+        // which also considers the taxonomy hierarchy.
+        $materialised_weight .= '.' . Number::intToAlphadecimal($ancestor->getWeight());
+        $this->hierarchy[$ancestor->id()] = ltrim($materialised_weight,  '.');
       }
     }
 
-    // Return the sort value.
-    if ($a->get('termWeight') === $b->get('termWeight')) {
-      return 0;
-    }
-    return ($a->get('termWeight') < $b->get('termWeight')) ? -1 : 1;
+    return $this->hierarchy[$a->getRawValue()] <=> $this->hierarchy[$b->getRawValue()];
   }
 
   /**