public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('category', EntityType::class, [
'class' => Category::class,
'query_builder' => function (CategoryRepository $er) {
return $er->getAllCategories();
}
]);
}

=======

class CategoryRepository extends EntityRepository
{
public function getAllCategories()
{
$qb = $this->getEntityManager()->createQueryBuilder()
->select('category')
->from('AppBundle:Category', 'category')
->leftjoin('category.translations', 'categoryTranslations')
->addSelect('categoryTranslations');
return $qb; //returns just QueryBuilder
}
}