Updated Drupal to 8.6. This goes with the following updates because it's possible...

[yaffs-website] / web / core / modules / serialization / src / Normalizer / EntityReferenceFieldItemNormalizerTrait.php

diff --git a/web/core/modules/serialization/src/Normalizer/EntityReferenceFieldItemNormalizerTrait.php b/web/core/modules/serialization/src/Normalizer/EntityReferenceFieldItemNormalizerTrait.php
new file mode 100644 (file)
index 0000000..1acfd70
--- /dev/null
+++ b/web/core/modules/serialization/src/Normalizer/EntityReferenceFieldItemNormalizerTrait.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Drupal\serialization\Normalizer;
+
+use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
+
+/**
+ * Converts empty reference values for entity reference items.
+ */
+trait EntityReferenceFieldItemNormalizerTrait {
+
+  protected function normalizeRootReferenceValue(&$values, EntityReferenceItem $field_item) {
+    // @todo Generalize for all tree-structured entity types.
+    if ($this->fieldItemReferencesTaxonomyTerm($field_item) && empty($values['target_id'])) {
+      $values['target_id'] = NULL;
+    }
+  }
+
+  /**
+   * Determines if a field item references a taxonomy term.
+   *
+   * @param \Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem $field_item
+   *
+   * @return bool
+   */
+  protected function fieldItemReferencesTaxonomyTerm(EntityReferenceItem $field_item) {
+    return $field_item->getFieldDefinition()->getSetting('target_type') === 'taxonomy_term';
+  }
+
+}