FactoryBasedController::prepareFieldsFromParams

protected function prepareFieldsFromParams(int $entityId, array $params): ?array
{
	$fields = null;
	if (isset($params['FIELDS']) && is_array($params['FIELDS']))
	{
		$fields = $params['FIELDS'];
	}

	if (empty($fields))
	{
		$item = $this->getFactory()->getItem($entityId);
		if (!is_null($item))
		{
			$fields = $item->getData();
		}
	}

	return $fields;
}