FieldWidgetConstraintValidator.php

<?php

declare (strict_types=1);
namespace Drupal\entity_test\Plugin\Validation\Constraint;

use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Validates the FieldWidgetConstraint constraint.
 */
class FieldWidgetConstraintValidator extends ConstraintValidator {
    
    /**
     * {@inheritdoc}
     */
    public function validate($field_item, Constraint $constraint) : void {
        $this->context
            ->addViolation($constraint->message);
    }

}