Strict ChoicesToValuesTransformer

ChoiceTypeExtension.php

<?php

namespace App\Form\TypeExtension;

use App\Form\DataTransformer\StrictChoicesToValuesTransformer;
use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Compoennt\Form\Extension\Core\DataTransformer\ChoicesToValuesTransformer;
use Symfony\Compoennt\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class ChoiceTypeExtension extends AbstractTypeExtension
{
    /**
     * {@inheritdoc}
     */
    public function getParent()
    {
        return ChoiceType::class;
    }
    
    /**
     * {@inheritdoc}
     */
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefault('strict', false);
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options = [])
    {
        if (!$options['strict'] || !$options['multiple']) {
            return;
        }

        $transformers = [];
        
        foreach($builder->getViewTransformers() as $transformer) {
            if ($transformer instanceof ChoicesToValuesTransformer) {
                $transformer = new StrictChoicesToValuesTransformer($transformer);
            }
            
            $transformers[] = $transformer;
        }
        
        $builder->resetViewTransformers();
        
        foreach($transformers as $transformer) {
            $builder->addViewTransformer($transformer);
        }
    }
}

services.yaml

services:
    App\Form\TypeExtension\StrictChoiceTypeExtension:
        tags:
            - name: form.type_extension
              extended_type: Symfony\Component\Form\Extension\Core\Type\ChoiceType

StrictChoicesToValuesTransformer.php

<?php

namespace App\Form\DataTransformer;

use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;
use Symfony\Component\Form\Extension\Core\DataTransformer\ChoicesToValuesTransformer;

class StrictChoicesToValuesTransformer implements DataTransformerInterface
{
    private $choicesToValuesTransformer;
    
    public function __construct(ChoicesToValuesTransformer $choicesToValuesTransformer)
    {
        $this->choicesToValuesTransformer = $choicesToValuesTransformer;
    }
    
    /**
     * {@inheritdoc}
     */
    public function transform($data)
    {
        if (null === $data || [] === $data) {
            return [];
        }

        $values = $this->choicesToValuesTransformer->transform($data);
        
        if (\count($data) !== \count($values)) {
            throw new TransformationFailedException('Count of choices and values mismatch.');
        }
        
        return $values;
    }
    
    /**
     * {@inheritdoc}
     */
    public function reverseTransform($data)
    {
        if (null === $data || [] === $data) {
            return [];
        }

        $choices = $this->choicesToValuesTransformer->reverseTransform($data);
        
        if (\count($data) !== \count($choices)) {
            throw new TransformationFailedException('Count of choices and values mismatch.');
        }

        return $choices;
    }
}