Symfony form extension to permit un-sorted "preferred_choices" option

ChoiceTypeExtension.php

<?php
declare(strict_types=1);

namespace AppBundle\Form\Extension;

use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\Form\FormView;
use Symfony\Component\OptionsResolver\OptionsResolver;

/**
 * Add option to choice field type to keep preferred_choices in the specified order
 */
class ChoiceTypeExtension extends AbstractTypeExtension
{

    /**
     * @return string
     */
    public function getExtendedType()
    {
        return ChoiceType::class;
    }

    /**
     * @param OptionsResolver $resolver
     */
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver
            ->setDefaults(['preferred_choices_unsorted' => false])
            ->setAllowedTypes('preferred_choices_unsorted', 'boolean');
    }

    /**
     * @param FormView      $view
     * @param FormInterface $form
     * @param array         $options
     */
    public function buildView(FormView $view, FormInterface $form, array $options)
    {
        parent::buildView($view, $form, $options);

        $parentDefinesUnsorted = $form->getParent()->getConfig()->getOption('preferred_choices_unsorted');

        // If preferred_choices are specified for this field, AND
        // If 'preferred_choices_unsorted' is specified by this field,
        // or by its parent (to support choices inside compound fields)
        if ($options['preferred_choices'] && ($options['preferred_choices_unsorted'] || $parentDefinesUnsorted))
        {
            $newPreferredChoices = array();

            foreach ($options['preferred_choices'] as $key)
            {
                $choice = $this->findChoiceView($view, $key);

                if (!$choice)
                {
                    continue;
                }

                $newPreferredChoices[$key] = $choice;
            }

            $view->vars['preferred_choices'] = $newPreferredChoices;
        }
    }

    /**
     * @param FormView $view
     * @param          $keyToFind
     *
     * @return null
     */
    private function findChoiceView(FormView $view, $keyToFind)
    {
        foreach ($view->vars['preferred_choices'] as $choice)
        {
            if ($choice->value == $keyToFind)
            {
                return $choice;
            }
        }

        return null;
    }

}

services.yml

AppBundle\Form\Extension\ChoiceTypeExtension:
  tags:
    - { name: form.type_extension, extended_type: Symfony\Component\Form\Extension\Core\Type\ChoiceType }