composer.json

@@ -16,9 +16,9 @@
   },
   "license": "GPL-2.0+",
   "require-dev": {
-    "drupal/search_api": "^1.25||1.x-dev",
-    "drupal/jquery_ui_slider": "~1.1",
-    "drupal/jquery_ui_touch_punch": "~1.0"
+    "drupal/search_api": "^1.28||1.x-dev",
+    "drupal/jquery_ui_slider": "~2.0",
+    "drupal/jquery_ui_touch_punch": "~1.1"
   },
   "suggest": {
     "drupal/jquery_ui_slider": "Required for the 'Facets Range Widget' module to work",

facets.post_update.php

+<?php
+
+/**
+ * @file
+ * Post-update functions for the Facets module.
+ */
+
+/**
+ * Add the hierarchy processor to facets that have the hierarchy enabled.
+ */
+function facets_post_update_8001_8001_8001_8001_8001_8001_8001_8001_add_hierarchy_processor() {
+  $config_factory = \Drupal::configFactory();
+
+  // Find all facets that have the hierarchy enabled, but do not use the
+  // hierarchy processor.
+  foreach ($config_factory->listAll('facets.facet.') as $facet_config_name) {
+    $facet = $config_factory->getEditable($facet_config_name);
+    if ($facet->get('use_hierarchy')) {
+      $processor_configs = $facet->get('processor_configs');
+      if (!isset($processor_configs['hierarchy_processor'])) {
+        // Enable the hierarchy processor.
+        $processor_configs['hierarchy_processor'] = [
+          'id' => 'hierarchy_processor',
+          'weights' => [
+            'build' => 100,
+          ],
+          'settings' => [],
+        ];
+        $facet->set('processor_configs', $processor_configs);
+        $facet->save(TRUE);
+      }
+    }
+  }
+}

src/Plugin/facets/processor/CombineFacetProcessor.php

@@ -18,7 +18,7 @@ use Symfony\Component\DependencyInjection\ContainerInterface;
  * @FacetsProcessor(
  *   id = "combine_processor",
  *   label = @Translation("Combine facets"),
- *   description = @Translation("Combine the results of two or more facets. The raw value of a result item is used to identify a resuls item. It is up to you to ensure that the combination of the result sets makes sense. As the combination bases on the raw calues it makes sense to place this processor on an early position, especially before the URL handler"),
+ *   description = @Translation("Combine the results of two or more facets. The raw value of a result item is used to identify a results item. It is up to you to ensure that the combination of the result sets makes sense. As the combination bases on the raw values it makes sense to place this processor on an early position, especially before the URL handler"),
  *   stages = {
  *     "build" = 5
  *   }