[GraphQL] How to create relation objects in mutation?

[oleg-brizy]

I want to create child entities (fields) in the same mutation

mutation {
  createCollectionType (input: {
      title: "Hello world",
      fields: [
        {
          title: "Field 1",
          type: text
        }
      ]
    }
  ) {
    collectionType { id }
  }
}

but I get error

{
  "errors": [
    {
      "debugMessage": "Nested documents for attribute \"fields\" are not allowed. Use IRIs instead.",
    }
  ]
}

I can't and don't want to use IRIs because it will require multiple mutations (server requests).

• Entity/Resource

/**
 * @ApiResource(
 *  graphql={
 *     "create"={
 *         "mutation"=CollectionTypeMutationResolver::class,
 *         "args"={
 *             "title"={"type"="String!"},
 *             "fields"={"type"="[CollectionTypeFieldInput!]"},
 *         },
 *     }
 *   }
 * )
 *
 * @ORM\Entity(...)
 */
class CollectionType
{
    ...

    /**
     * @ORM\OneToMany(targetEntity="CollectionTypeField", mappedBy="collectionType", cascade={"persist", "remove"})
     * @ORM\OrderBy({"priority": "DESC"})
     *
     * @Assert\Valid()
     */
    private $fields;

CollectionTypeMutationResolver is empty (just return).

• collectionTypeFieldInput type (not so relevant)

final class CollectionTypeFieldInputType extends InputObjectType implements TypeInterface
{
    public function __construct(array $config = [])
    {
        $config['fields'] = [
            'title' => Type::nonNull(Type::string()),
            'type' => Type::nonNull(MyTypeRegistry::collectionFieldType()),
        ];

        parent::__construct($config);
    }
}

---

I tried to rename arg to "createFields" to not match entity property, to bypass the "Nested documents are not allowed".

```php
/**
 * @ApiResource(
 *  graphql={
 *     "create"={
 *         "args"={
 *             "createFields"={"type"="[CollectionTypeFieldInput!]"},
 *         },
 *     }
 *   }
 * )
 */

Then in resolver to populate entity fields property from createFields mutation arg

final class CollectionTypeMutationResolver implements MutationResolverInterface
{
    public function __invoke($item, array $context)
    {
        $fields = new ArrayCollection();
        foreach ($context['args']['input']['createFields'] as $fieldArgs) { print_r($fieldArgs);
            $field = new CollectionTypeField();
            $field->setCollectionType($item);
            $field->setTitle($fieldArgs['title']);
            $field->setType($fieldArgs['type']);
            if (isset($fieldArgs['priority'])) {
                $field->setPriority($fieldArgs['priority']);
            }
            if (isset($fieldArgs['required'])) {
                $field->setRequired($fieldArgs['required']);
            }
        }
        $item->setFields($fields);

        return $item;
    }
}

The entity is created but child entities are not validated and not created. Seems like resolver is executed right before save after $item was persisted (I have read the docs but still don't understand when exactly, after/before what stage, the resolver is executed).

---

How to create a mutation that creates nested relations (one/any level) ?

[oleg-brizy]

#3258 (comment)