I have the same on 4.4.8

Cannot reproduce this on 4.4.8

I have the same on 4.4.8 with Required and Òptional constraint.
No error on 4.4.7.

Can anyone provide a small reproducer?

For me this works fine on 4.4.8:

<?php

require_once 'vendor/autoload.php';

use Symfony\Component\Validator\Constraints\All;
use Symfony\Component\Validator\Constraints\Choice;
use Symfony\Component\Validator\Constraints\Collection;
use Symfony\Component\Validator\Constraints\Email;
use Symfony\Component\Validator\Constraints\NotBlank;
use Symfony\Component\Validator\Constraints\Required;

$kernel = new AppKernel('dev', true);
$kernel->boot();

$violations = $kernel->getContainer()->get('validator')->validate([[]], new All([
    new Collection([
        'email' => [
            new NotBlank(),
            new Email(),
        ],
        'verified' => [
            new Required(),
            new Choice(['strict' => true, 'choices' => [1, 0, "1", "0", true, false]]),
        ],
    ]),
]));

dump($violations);

@dmaicher

<?php

require dirname(__DIR__).'/config/bootstrap.php';

use Symfony\Component\Validator\Constraints\Required;

$kernel = new \App\Kernel('dev', true);
$kernel->boot();

$violations = $kernel->getContainer()->get('validator')->validate(null, [
    new Required(),
]);

dump($violations);

In my case this prints for 4.4.8:

Constraint validator "Symfony\Component\Validator\Constraints\RequiredValidator" does not exist or is not enabled. Check the "validatedBy" method in your constraint class "Symfony\Component\Validator\Constraints\Required".

and for 4.4.7:

Symfony\Component\Validator\ConstraintViolationList {#712
  -violations: []
}

The best would be if one of you could provide a small example application allowing to reproduce the issue as suggested by @dmaicher.

@xabbuh Here reproducer for a bug! Reproducer

Status: reviewed

In my case the issue was reproduced on 4.4.8

the code created for symfony 3.3.36 and now updated to the 4.4.8. After this update I experienced the issue.

Just for test I downgraded 4.4.8 -> 4.4.7 and could not reproduce the issue.

After that I updated to 4.4.8 again. And everything works and the issue not reproduced

@R11baka Thank you, I was able to reproduce. The behaviour changes is related to #36365. I don't know how we could achieve both (the solved issue and the way the constraint is used in the example). However, using the Required constraint in the way as in the reproducer doesn't make much sense. So I am not sure if we really need to change anything.

/cc @HeahDude

@xabbuh I'm using the Required constraint in a form in the constraints array. Just modify the controller in @R11baka's reproducer to:

<?php

namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Validator\Validator\ValidatorInterface;
use Symfony\Component\Validator\Constraints\Required;
use Symfony\Component\Form\Extension\Core\Type\HiddenType;
use Symfony\Component\HttpFoundation\Request;

class Test extends AbstractController
{

    public function test(Request $request){
        $form = $this->get('form.factory')->createNamedBuilder('testForm')
                ->add('test', HiddenType::class, [ 'constraints' => [ new Required() ] ])
                ->getForm();
        $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
                dump('valid');
        }

        dump('not submitted');
    }

}

Then require symfony/form via composer, restart the symfony web server, openhttp://127.0.0.1:8000/?testForm[test]=foo and the output is:

Constraint validator "Symfony\Component\Validator\Constraints\RequiredValidator" does not exist or is not enabled. Check the "validatedBy" method in your constraint class "Symfony\Component\Validator\Constraints\Required". (500 Internal Server Error)

Is this an unsupported use case for constraints?

Basically yes, or to be more precise: Before the constraint placed in this way was just useless (i.e. there was no difference in having it or not). The Required constraint is meant to be used inside a Collection constraint: https://symfony.com/doc/current/reference/constraints/Collection.html#required-and-optional-field-constraints

@codegain I'm quite sure that your use case was actually to use NotBlank, not Required

@stof Currently I use the Optional constraint like this:

'constraints' => [
    (null === $someVariable) ? new NotBlank() : new Optional(),
]

I know there are other mechanisms like validation groups but that seemed to be the easiest option since null is not allowed. It seems I will have to rewrite some of these forms if this is no longer possible.

see #36894