Support custom Symfony Validation Constraint

[Kocal]

Hello, I'm encountering an issue with custom Validation Constraint.

PhpStan returns me this error:

 ------ ----------------------------------------------------------------------------------- 
  Line   common/Bundle/Common/CoreBundle/Validator/Constraints/IsStringValidator.php        
 ------ ----------------------------------------------------------------------------------- 
  21     Access to an undefined property Symfony\Component\Validator\Constraint::$message.  
 ------ ----------------------------------------------------------------------------------- 

This is my code (just an example, not for production 😄) :

<?php
// packages/common/Bundle/Common/CoreBundle/Validator/Constraints/IsStringValidator.php

declare(strict_types=1);

namespace Yprox\Bundle\Common\CoreBundle\Validator\Constraints;

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

class IsStringValidator extends ConstraintValidator
{
    /**
     * {@inheritdoc}
     */
    public function validate($value, Constraint $constraint)
    {
        if (null === $value || is_string($value)) {
            return true;
        }

        $this->context->addViolation($constraint->message);

        return false;
    }
}

<?php
// packages/common/Bundle/Common/CoreBundle/Validator/Constraints/IsString.php

declare(strict_types=1);

namespace Yprox\Bundle\Common\CoreBundle\Validator\Constraints;

use Symfony\Component\Validator\Constraint;

/**
 * @Annotation
 */
class IsString extends Constraint
{
    public $message = 'Value must be a string';
}

And this is normal, because there is no property $message on abstrac class Symfony\Component\Validator\Constraint.

---

I tried to update my code to this:

/**
 * {@inheritdoc}
 */
public function validate($value, IsString $constraint)

but I can't because the declaration is not compatible with ConstraintValidatorInterface::validate($value, Constraint $constraint).

So I tried with a PHPDoc like this:

/**
 * {@inheritdoc}
 * @param IsString $constraint
 */
public function validate($value, Constraint $constraint)

but I still have the same error from PhpStan.

---

Is there any workaround for that? Should I ignore this error by configuring PhpStan?

Maybe PhpStan can automatically call Constraint#validatedBy()? I'm not sure about that 😕 ...

Thank you! 🙂

[lookyman]

For now, just ignore the error in PHPStan's config. But I will look into what can be done about it. Haven't really worked with the validation component before, so it may take a while..

[Kocal]

Okay thanks 👍

[lookyman]

Also, maybe you could probably just add something like assert($constraint instanceof IsString); into the IsStringValidator::validate() method..

[alcaeus]

Pretty much every Symfony constraint does exactly that: https://github.com/symfony/symfony/blob/2bfcaeb31ff3b878734b0951851d25abf2b3321e/src/Symfony/Component/Validator/Constraints/NotNullValidator.php#L28. There should not be any magic involved with this: I could easily create a FooConstraint that returns YourValidator::class in its validatedBy method, and all of a sudden YourValidator::validate would run into a fatal error because it receives a constraint class it doesn't expect or understand. In this case, you want to make sure you're given the correct type instead of assuming some magic to do so.

I suggest closing this issue as there's nothing to fix: asserting against the constraint class is exactly what should be done.

[Kocal]

Oh, I didn't know Symfony check for Constraint instance.
Well, I will do the same, thanks you guys!

[ismail1432]

Thanks @alcaeus 👍

[github-actions]

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