Support data field

Your array function

'fields' => fn() => $subFields,

Needs to have array keys. The key is the field name.

You're returning:

[
  0 => ['type'..., 'description'],
  1 => ['type'..., 'description'],
]

You need to return something like.

[
  $name => ['type'..., 'description'],
]

Try this:

        $types[$field->getTypeSdl()] = new ObjectType([
          'name' => $field->getTypeSdl(),
          'description' => (string) $this->t('A data field is a specialty field provided by the CMS.'),
          'fields' => function () use ($field) {
            $columns = array_keys($field->getFieldDefinition()->getSetting('columns'));
            $subFields = [];
            foreach ($columns as $column) {
              $subFields[$column] = [
                'type' => static::type($field->getSubfieldTypeSdl($column)),
                'description' => (string) $this->t('The @field value of the data field', ['@field' => $column]),
              ];
            }
            return $subFields;
          },
        ]);

This makes it appear in the schema.

You'll then need to do a bit of work in your `DataFieldItem` class to return the correct value.

thanks i change to

        $subFields = array_combine($columns, array_map(function ($name) use ($field) {
          return [
            'type' => static::type($field->getSubfieldTypeSdl($name)),
            'description' => (string) $this->t('The @field value of the data field', ['@field' => $name]),
          ];
        }, $columns));

Error gone.
I got values brut, Now i need to convert id of entity reference, file to object, uri id to link, it must do logic in resolveFieldItem

  public function resolveFieldItem(FieldItemInterface $item, FieldContext $context) {
    $columns = array_keys($this->getFieldDefinition()->getSetting('columns'));
    $subfields = [];
    foreach ($columns as $subfield) {
      $subfields[$subfield] = $this->getSubField($subfield, $item, $context) ?: NULL;
    }
    return $subfields;
  }

do you have any service or helper to convert to graphql compose format?

Hello,
I tried the data field with the subfield as the entity reference. It only shows the nid but I want all the node's field value like jsonapi. i try converting object node to array.
In explorer it shows NULL in subfield, what did I do wrong?

  protected function getSubField(string $subfield, FieldItemInterface $item, FieldContext $context) {
    $value = $item->{$subfield};

    // Attempt to load the plugin for the field type.
    $plugin = $this->getSubfieldPlugin($subfield);
    if (!$plugin) {
      return $value;
    }
    $storageSettings = $item->getFieldDefinition()->getSetting('columns')[$subfield];
    $fieldSettings = $item->getFieldDefinition()->getSetting('field_settings')[$subfield];
    if ($storageSettings["type"] == 'entity_reference' && is_numeric($value)) {
      $entity = \Drupal::entityTypeManager()->getStorage($fieldSettings["entity_reference_type"])->load($value);
      $value = [];
      foreach ($entity->getFields() as $name => $field) {
        $value[$name] = $field->getString();
      }
      return $value;
    }

Please support datafield with entity
I try but it doesn't work smothly
https://git.drupalcode.org/project/datafield/-/blob/2.x/src/Plugin/Graph...

protected function getSubField(string $subfield, FieldItemInterface $item, FieldContext $context) {
    $value = $item->{$subfield};

    // Attempt to load the plugin for the field type.
    $plugin = $this->getSubfieldPlugin($subfield);
    if (!$plugin) {
      return $value;
    }
    $storageSettings = $item->getFieldDefinition()->getSetting('columns')[$subfield];
    $fieldSettings = $item->getFieldDefinition()->getSetting('field_settings')[$subfield];
    if ($storageSettings["type"] == 'entity_reference' && is_numeric($value)) {
      $entity = \Drupal::entityTypeManager()->getStorage($fieldSettings["entity_reference_type"])->load($value);
      $item->set('entity', $entity);
      $value = $entity->uuid();
    }
    if ($storageSettings["type"] == 'file' && is_numeric($value)) {
      $entity = \Drupal::entityTypeManager()->getStorage('file')->load($value);
      $item->set('entity', $entity);
    }
    // Check if it has a resolver we can hijack.
    $class = new \ReflectionClass($plugin['class']);
    if (!$class->implementsInterface(FieldProducerItemInterface::class)) {
      return $value;
    }

    // Create an instance of the graphql plugin.
    $instance = $this->gqlFieldTypeManager->createInstance($plugin['id'], []);

    // Clone the current item into a new object for safety.
    $clone = clone $item;

    // Generically set the value. Relies on magic method __set().
    $clone->value = $value;

    // Call the plugin resolver on the subfield.
    return $instance->resolveFieldItem($clone, $context);
  }