FormOptionReplacer.php

<?php

namespace CuatroOchenta\BackOfficeBundle\Form;

use Symfony\Component\Form\FormConfigInterface;
use Symfony\Component\Form\FormInterface;

class FormOptionReplacer
{
    /**
     * @param FormInterface $builder
     * @param $property
     * @param array $newOptions
     * @return void
     */
    public static function replace(FormInterface $builder, $property, array $newOptions)
    {
        /** @var FormConfigInterface $config */
        $config = $builder->get($property)->getConfig();
        $options = $config->getOptions();
        $type = $config->getType();

        $builder->add($config->getName(), $type->getName(), array_replace($options, $newOptions));
    }
}