Mongo ODM Unique Assert

UniqueInCollection.php

<?php declare(strict_types=1);

namespace App\Validator\Constraints;

use Symfony\Component\Validator\Constraint;

/**
 * @Annotation
 */
class UniqueInCollection extends Constraint
{
    public string $message = 'The value "{{ value }}" is already taken.';
}

UniqueInCollectionValidator.php

<?php declare(strict_types=1);

namespace App\Validator\Constraints;

use Doctrine\ODM\MongoDB\DocumentManager;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
use Symfony\Component\Validator\Exception\UnexpectedValueException;

class UniqueInCollectionValidator extends ConstraintValidator
{
    public function __construct(private DocumentManager $dm) {}

    public function validate($value, Constraint $constraint)
    {
        if (null === $value || '' === $value) {
            return;
        }

        if (!is_string($value)) {
            throw new UnexpectedValueException($value, 'string');
        }

        if ($this->dm->getRepository($this->context->getClassName())
            ->findOneBy([$this->context->getPropertyName() => $value])) {
            $this->context->buildViolation($constraint->message)
                ->setParameter('{{ value }}', $value)
                ->addViolation();
        }
    }
}

YourClass.php

<?php declare(strict_types=1);

use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;
use Symfony\Component\Validator\Constraints as Assert;
use App\Validator\Constraints as AppAssert; // <-- this is the new custom assertion

/**
 * @ODM\Document(collection="guides")
 */
class YourClass
{
    /**
     * @ODM\Field(type="string")
     *
     * @AppAssert\UniqueInCollection
     * @Assert\NotBlank()
     * @Assert\Length(
     *     min=6,
     *     max=120
     * )
     */
    private string $propThatShouldBeUniqueInCollection = '';
}