ConstraintValidatorFactory.php

<?php

namespace Drupal\Core\Validation;

use Drupal\Core\DependencyInjection\ClassResolverInterface;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidatorFactory as BaseConstraintValidatorFactory;
use Symfony\Component\Validator\ConstraintValidatorInterface;

/**
 * Defines a constraint validator factory that works with container injection.
 *
 * @TODO Decide what to do with this class or how to reuse constraint
 * validators in https://drupal.org/project/drupal/issues/3097071
 */
class ConstraintValidatorFactory extends BaseConstraintValidatorFactory {
    
    /**
     * The class resolver.
     */
    protected $classResolver;
    
    /**
     * Constructs a new ConstraintValidatorFactory.
     *
     * @param \Drupal\Core\DependencyInjection\ClassResolverInterface $class_resolver
     *   The class resolver.
     */
    public function __construct(ClassResolverInterface $class_resolver) {
        $this->classResolver = $class_resolver;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getInstance(Constraint $constraint) : ConstraintValidatorInterface {
        $class_name = $constraint->validatedBy();
        // Constraint validator instances should always be initialized newly and
        // never shared, because the current validation context is getting injected
        // into them through setter injection and in a case of a recursive
        // validation where a validator triggers a validation chain leading to the
        // same validator the context of the first call would be exchanged with the
        // one of the subsequent validation chain.
        return $this->classResolver
            ->getInstanceFromDefinition($class_name);
    }

}