Use InputUnionType for updating related existing resources

Author: alanpoulain

features/graphql/mutation.feature

@@ -122,6 +122,28 @@ Feature: GraphQL mutation support
     And the JSON node "data.createRelatedDummy.id" should be equal to "/related_dummies/2"
     And the JSON node "data.createRelatedDummy.clientMutationId" should be equal to "myId"
 
+  Scenario: Create an item and update a nested resource through a mutation
+    When I send the following GraphQL request:
+    """
+    mutation {
+      createRelationEmbedder(input: {paris: "paris", krondstadt: "Krondstadt", anotherRelated: {id: 2, symfony: "laravel"}, clientMutationId: "myId"}) {
+        id
+        anotherRelated {
+          id
+          symfony
+        }
+        clientMutationId
+      }
+    }
+    """
+    Then the response status code should be 200
+    And the response should be in JSON
+    And the header "Content-Type" should be equal to "application/json"
+    And the JSON node "data.createRelationEmbedder.id" should be equal to "/relation_embedders/1"
+    And the JSON node "data.createRelationEmbedder.anotherRelated.id" should be equal to "/related_dummies/2"
+    And the JSON node "data.createRelationEmbedder.anotherRelated.symfony" should be equal to "laravel"
+    And the JSON node "data.createRelationEmbedder.clientMutationId" should be equal to "myId"
+
   Scenario: Delete an item through a mutation
     When I send the following GraphQL request:
     """

src/GraphQl/Serializer/ItemNormalizer.php

@@ -23,13 +23,14 @@
 
 use ApiPlatform\Core\Metadata\Property\PropertyMetadata;
 use ApiPlatform\Core\Serializer\AbstractItemNormalizer;
+use ApiPlatform\Core\Serializer\ItemNormalizer as GenericItemNormalizer;
 
 /**
  * GraphQL normalizer.
  *
  * @author Kévin Dunglas <[email protected]>
  */
-final class ItemNormalizer extends AbstractItemNormalizer
+final class ItemNormalizer extends GenericItemNormalizer
 {
     const FORMAT = 'graphql';
     const ITEM_KEY = '#item';
@@ -39,7 +40,7 @@ final class ItemNormalizer extends AbstractItemNormalizer
      */
     public function normalize($object, $format = null, array $context = [])
     {
-        $data = parent::normalize($object, $format, $context);
+        $data = AbstractItemNormalizer::normalize($object, $format, $context);
         $data[self::ITEM_KEY] = serialize($object); // calling serialize prevent weird normalization process done by Webonyx's GraphQL PHP
 
         return $data;