Merge pull request #16428 from craftcms/bugfix/16191-lazy-eager-loadi…

…ng-and-multi-instance-relation-field

When normalising relation field value, respect the empty array

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Fixed a bug where field layout elements’ action menus could have an empty action group.
 - Fixed a bug where Single section entries could be duplicated after running the `entry-types/merge` command. ([#16394](https://github.com/craftcms/cms/issues/16394))
 - Fixed a styling bug with the system message modal. ([#16410](https://github.com/craftcms/cms/issues/16410))
+- Fixed a bug where relational fields could eager-load elements from a different instance of the same field, if one of the instances had no relations. ([#16191](https://github.com/craftcms/cms/issues/16191))
 
 ## 5.5.9 - 2025-01-06
 

src/fields/BaseRelationField.php

@@ -669,12 +669,9 @@ public function normalizeValue(mixed $value, ?ElementInterface $element): mixed
 
         if (is_array($value)) {
             $value = array_values(array_filter($value));
+            $query->andWhere(['elements.id' => $value]);
             if (!empty($value)) {
-                $query
-                    ->andWhere(['elements.id' => $value])
-                    ->orderBy([new FixedOrderExpression('elements.id', $value, Craft::$app->getDb())]);
-            } else {
-                $query->andWhere('0 = 1');
+                $query->orderBy([new FixedOrderExpression('elements.id', $value, Craft::$app->getDb())]);
             }
         } elseif ($value === null && $element?->id && $this->isFirstInstance($element)) {
             // If $value is null, the element + field haven’t been saved since updating to Craft 5.3+,