UserMailRequired.php

<?php

namespace Drupal\user\Plugin\Validation\Constraint;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\Core\Validation\Attribute\Constraint;
use Symfony\Component\Validator\Constraint as SymfonyConstraint;

/**
 * Checks if the user's email address is provided if required.
 *
 * The user mail field is NOT required if account originally had no mail set
 * and the user performing the edit has 'administer users' permission.
 * This allows users without email address to be edited and deleted.
 */
class UserMailRequired extends SymfonyConstraint {
    
    /**
     * Violation message. Use the same message as FormValidator.
     *
     * Note that the name argument is not sanitized so that translators only have
     * one string to translate. The name is sanitized in self::validate().
     *
     * @var string
     */
    public $message = '@name field is required.';

}