Symfony Entity Tree ( Hierarchy ) Form Type

EntityTreeType.php

<?php
/**
 * (c) Masoud Zohrabi <[email protected]>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Mdzzohrabi\Form;

use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\ChoiceList\View\ChoiceView;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\Form\FormView;
use Symfony\Component\OptionsResolver\OptionsResolver;

/**
 * Class EntityTreeType
 * @package Mdzzohrabi\Form
 */
class EntityTreeType extends AbstractType {

    public function buildView( FormView $view , FormInterface $form , array $options ) {

        $choices = [];

        foreach ( $view->vars['choices'] as $choice ) {
            if ( $choice->data->getParent() === null )
            $choices[ $choice->value ] = $choice->data;
        }

        $choices = $this->buildTreeChoices( $choices );

        $view->vars['choices'] = $choices;

    }

    /**
     * @param object[] $choices
     * @param int $level
     * @return array
     */
    protected function buildTreeChoices( $choices , $level = 0 ) {

        $result = array();

        foreach ( $choices as $choice ){

            $result[ $choice->getId() ] = new ChoiceView(
                $choice,
                (string)$choice->getId(),
                str_repeat( '--' , $level ) . ' ' . $choice->getName(),
                []
            );

            if ( !$choice->getChilds()->isEmpty() )
            $result = array_merge(
                $result,
                $this->buildTreeChoices( $choice->getChilds() , $level + 1 )
            );

        }

        return $result;

    }

    public function getParent() {
        return EntityType::class;
    }

}

FIX BUG

$result = array_merge(
        $result,
        [new ChoiceView(
                $choice,
                (string)$choice->getId(),
                str_repeat($options['prefix'], $level) . ' ' . $choice->getName(),
                []
            )]
        );
if (!$choice->$children_method_name()->isEmpty())
    $result = array_merge(
        $result,
        $this->buildTreeChoices($choice->$children_method_name(), $options, $level + 1)
    );

Hello!
Thank you for share this code!

It works fine when "multiple" and "expanded" are false, but:

'multiple' => true,
'expanded' => true,

Choices generated by this class are overridden by original EntityType class, losing hierarchy and order.
How can we do?
Thank you!