Brad Jones
--- a/core/lib/Drupal/Core/Field/EmptyFieldItemListCacheabilityInterface.php 0 → 100644
+++ b/core/lib/Drupal/Core/Field/EmptyFieldItemListCacheabilityInterface.php 0 → 100644
+<?php
+
+namespace Drupal\Core\Field;
+
+use Drupal\Core\Cache\CacheableMetadata;
+
+/**
+ * Interface for field item lists which have cacheable metadata for empty state.
+ *
+ * Field item lists should implement this interface when their being empty
+ * results from a condition with cacheability distinct from its parent. For
+ * instance, computed fields may change their value due to entity CRUD events
+ * orthogonal to the parent entity itself. Non-empty lists would continue to
+ * yield cacheable metadata (e.g., during serialization) via their items.
+ */
+interface EmptyFieldItemListCacheabilityInterface {
--- a/core/modules/jsonapi/src/JsonApiResource/ResourceIdentifier.php
+++ b/core/modules/jsonapi/src/JsonApiResource/ResourceIdentifier.php
   * @return string
   *   The property name which has an entity as its value.
   */
-  protected static function getDataReferencePropertyName(EntityReferenceItem $item) {
+  public static function getDataReferencePropertyName(EntityReferenceItem $item) {
--- a/core/modules/jsonapi/src/Normalizer/FieldNormalizer.php
+++ b/core/modules/jsonapi/src/Normalizer/FieldNormalizer.php
    $normalized_items = $this->normalizeFieldItems($field, $format, $context);
    assert($context['resource_object'] instanceof ResourceObject);
    return $context['resource_object']->getResourceType()->getFieldByInternalName($field->getName())->hasOne()
-      ? array_shift($normalized_items) ?: CacheableNormalization::permanent(NULL)
+      ? array_shift($normalized_items)
+        ?: new CacheableNormalization(
+          $field instanceof EmptyFieldItemListCacheabilityInterface
+            ? $field->getEmptyListCacheability()
+            : new CacheableMetadata(),
+          NULL
+        )