remove relations for fields that are not part of the layout anymore

CHANGELOG-WIP.md

@@ -5,3 +5,9 @@
 
 ### Development
 - The `{% js %}` and `{% css %}` tags now support `.js.gz` and `.css.gz` URLs. ([#14243](https://github.com/craftcms/cms/issues/14243))
+
+### Extensibility
+- Added `craft\services\Relations::deleteLeftoverRelations()`. ([#13956](https://github.com/craftcms/cms/issues/13956))
+
+### System
+- Relations for fields that are no longer included in an element’s field layout are now deleted after element save. ([#13956](https://github.com/craftcms/cms/issues/13956))

src/base/Element.php

@@ -5182,6 +5182,11 @@ public function afterPropagate(bool $isNew): void
             $field->afterElementPropagate($this, $isNew);
         }
 
+        // Delete relations that don’t belong to a relational field on the element's field layout
+        if (!ElementHelper::isDraftOrRevision($this)) {
+            Craft::$app->getRelations()->deleteLeftoverRelations($this);
+        }
+
         // Trigger an 'afterPropagate' event
         if ($this->hasEventHandlers(self::EVENT_AFTER_PROPAGATE)) {
             $this->trigger(self::EVENT_AFTER_PROPAGATE, new ModelEvent([

src/services/Relations.php

@@ -12,6 +12,7 @@
 use craft\db\Command;
 use craft\db\Query;
 use craft\db\Table;
+use craft\fieldlayoutelements\CustomField;
 use craft\fields\BaseRelationField;
 use craft\helpers\Db;
 use Throwable;
@@ -125,4 +126,51 @@ public function saveRelations(BaseRelationField $field, ElementInterface $source
             }
         }
     }
+
+    /**
+     * Deletes relations that don’t belong to a relational field on the given element’s field layout.
+     *
+     * @param ElementInterface $element
+     * @since 4.8.0
+     */
+    public function deleteLeftoverRelations(ElementInterface $element): void
+    {
+        if (!$element->id) {
+            return;
+        }
+
+        $fieldLayout = $element->getFieldLayout();
+        if (!$fieldLayout) {
+            return;
+        }
+
+        $relationFieldIds = [];
+        foreach ($fieldLayout->getTabs() as $tab) {
+            foreach ($tab->getElements() as $layoutElement) {
+                if ($layoutElement instanceof CustomField) {
+                    $field = $layoutElement->getField();
+                    if ($field instanceof BaseRelationField) {
+                        $relationFieldIds[] = $field->id;
+                    }
+                }
+            }
+        }
+
+        // get those relations for the element that don't belong to any relational fields that are in the layout
+        $query = (new Query())
+            ->select(['id'])
+            ->from(Table::RELATIONS)
+            ->where(['sourceId' => $element->id]);
+
+        if (!empty($relationFieldIds)) {
+            $query->andWhere(['not', ['fieldId' => $relationFieldIds]]);
+        }
+
+        $leftoverRelationIds = $query->column();
+
+        // if relations were returned - delete them
+        if (!empty($leftoverRelationIds)) {
+            Db::delete(Table::RELATIONS, ['id' => $leftoverRelationIds]);
+        }
+    }
 }