Custom constraint with dependencies needs an alias

[samuel4x4]

It seems that Symfony 2.7 still needs an alias for the service declared for a custom constraint. Otherwise, it's not loaded as a service from the container, so the dependencies are not injected.

A. Failing example, without alias

Service declaration:

validator.custom_less_than:
    class: AppBundle\Validator\Constraints\CustomLessThanValidator
    arguments: ['@service_container']
    tags:
        - { name: validator.constraint_validator}

Constraint:

class CustomLessThan extends Constraint
{
	public $message = 'The value should be lett than "%lessThan%".';
}

Validator:

class CustomLessThanValidator extends ConstraintValidator 
{
	use ContainerAwareTrait;

	public function __construct(ContainerInterface $service_container)
	{
		$this->setContainer($service_container);
	}

	public function validate($value, Constraint $constraint)
	{
		$lessThanValue = $this->container->getParameter('less_than_value');
			   
		if ($value > $lessThanValue)
		{
			$this->context->buildViolation($constraint->message)
					->setParameter('%lessThan%', $lessThanValue)
					->addViolation();
		}
	}
}

Result:

Catchable Fatal Error: Argument 1 passed to AppBundle\Validator\Constraints\CustomLessThanValidator::__construct() must be an instance of Symfony\Component\DependencyInjection\Container, none given, called in vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Validator\ConstraintValidatorFactory.php on line 71 and defined
500 Internal Server Error - ContextErrorException

B. Working example, using alias

Service declaration:

validator.custom_less_than:
    class: AppBundle\Validator\Constraints\CustomLessThanValidator
    arguments: ['@service_container']
    tags:
        - { name: validator.constraint_validator, alias: 'alias.validator.custom_less_than' }

Constraint:

class CustomLessThan extends Constraint
{
	public $message = 'The value should be lett than "%lessThan%".';

	public function validatedBy()
	{
		return 'alias.validator.custom_less_than';
	}
}

Validator:

class CustomLessThanValidator extends ConstraintValidator 
{
	use ContainerAwareTrait;

	public function __construct(ContainerInterface $service_container)
	{
		$this->setContainer($service_container);
	}

	public function validate($value, Constraint $constraint)
	{
		$lessThanValue = $this->container->getParameter('less_than_value');
			   
		if ($value > $lessThanValue)
		{
			$this->context->buildViolation($constraint->message)
					->setParameter('%lessThan%', $lessThanValue)
					->addViolation();
		}
	}
}

Result:

No exception, the field is validated, the constraint message is displayed, containing the parameters value taken from Container

[xabbuh]

This should not be necessary. Can you show an minimal example that would fail without the alias?

[samuel4x4]

Hi @xabbuh, please check the PR description, I put there some examples. Thanks.

[xabbuh]

@samuel4x4 Are your constraint and the validator in the same namespace? Could you fork the Symfony Standard Edition and make the changes that are needed to reproduce your issue?

[samuel4x4]

Hi @xabbuh, I'm not sure I understand your request. I get that exception on my project based on Symfony 2.7.9 framework, as it is, nothing is changed on it. What should should I change if I fork it? Thanks.

[xabbuh]

Well, we do not have access to your project to reproduce your issue. But if you can take the default Symfony Standard Edition and make the changes that replicate the behaviour in your application, we should be able to help you. By the way, the displayed error message has been improved in more recent 2.7 releases. Maybe that can help you too.

[samuel4x4]

Hi @xabbuh, I hoped the provided code lines will clarify the issue. If they're not enough, I'll create a project in on GitHub based on Symfony Standard Edition 2.7.9, then I'll create a simple form with a custom constraint that should replicate my issue.

[xabbuh]

@samuel4x4 Sorry, unfortunately it's not. So it would indeed be great if you could that.

[xabbuh]

@samuel4x4 Did you manage to get further with your issue?

[javiereguiluz]

There's some confusion about this "alias" thing. See symfony/symfony#21610 for an explanation about this feature. I'm closing this as duplicated of #6610 which we're trying to fix in #7489. Thanks!