Issue #3498459: Incorrect condition groups nesting leads to incorrect facets count

modules/jsonapi_search_api_facets/tests/src/Functional/IndexFacetsTest.php

@@ -272,7 +272,7 @@ final class IndexFacetsTest extends BrowserTestBase {
         'condition' => [
           'path' => 'keywords',
           'operator' => 'IN',
-          'value' => ['grape', 'strawberry'],
+          'value' => ['grape', 'strawberry', 'banana', 'apple'],
         ],
       ],
     ];

src/Resource/IndexResource.php

@@ -21,6 +21,8 @@ use Drupal\search_api\IndexInterface;
 use Drupal\search_api\Item\ItemInterface;
 use Drupal\search_api\ParseMode\ParseModeInterface;
 use Drupal\search_api\ParseMode\ParseModePluginManager;
+use Drupal\search_api\Query\ConditionGroupInterface;
+use Drupal\search_api\Query\ConditionInterface;
 use Drupal\search_api\Query\QueryInterface;
 use Drupal\search_api\SearchApiException;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -170,7 +172,18 @@ final class IndexResource extends EntityResourceBase implements ContainerInjecti
     }
     try {
       $filter = Filter::createFromQueryParameter($filter);
-      $query->addConditionGroup($filter->queryCondition($query));
+
+      $root_group = $query->getConditionGroup();
+      $new_group = $filter->queryCondition($query);
+
+      foreach ($new_group->getConditions() as $element) {
+        if ($element instanceof ConditionInterface) {
+          $root_group->addCondition($element->getField(), $element->getValue(), $element->getOperator());
+        }
+        elseif ($element instanceof ConditionGroupInterface) {
+          $root_group->addConditionGroup($element);
+        }
+      }
     }
     catch (\Exception $exception) {
       throw new CacheableBadRequestHttpException($cacheability, $exception->getMessage());