[Best Practices] ConstraintViolationList & i18n

[bpolaszek]

Hello there,

Consider the following entity:

use ApiPlatform\Core\Annotation\ApiResource;
use Symfony\Component\Validator\Constraints as Assert;

#[ApiResource]
class SomeResource {
   #[Assert\Count(max: 10)]
   public array $items;
}

Whenever an API consumer (the JS app) populates items with more than 10 elements, it gets the following response:

{
  "@context": "/api/contexts/ConstraintViolationList",
  "@type": "ConstraintViolationList",
  "hydra:title": "An error occurred",
  "hydra:description": "items: This collection should contain 10 elements or less.",
  "violations": [
    {
      "propertyPath": "items",
      "message": "This collection should contain 10 elements or less.",
      "code": "756b1212-697c-468d-a9ad-50dd783bb169"
    }
  ]
}

However, for non-english speakers, some validation error messages are pretty hard to understand (and make the reading inconsistent as different languages are mixed).
So, I thought about mapping violations[*].code to a set of xlated messages on the front-end side, except I cannot easily access the variable(s) that triggered the violation (here: max with a value of 10).

What's the best way to tackle this? I assume I'm not the 1st one to face that issue.

Thanks,
Ben

[alanpoulain]

Hello,
Symfony validation messages are all translated in a lot of languages.
If the locale is correctly set, the message will be translated.
If you really want to access the parameters, we could add it optionally in the AbstractConstraintViolationListNormalizer but I'm not sure it's really needed.
You can also decorate the ConstraintViolationListNormalizer to add the logic yourself.

[bpolaszek]

Hey @alanpoulain,

Thanks for the quick reply.

Looks like it doesn't care about the locale, as ConstraintViolationList responses are always in English (not only on my side, but I also have customers complaints about this).

Just checked against Chrome devtools, which properly sends Accept-Language: fr-FR,fr;q=0.9,en-US;q=0.8,en;q=0.7.
Is there something I misconfigured on the API side?

[alanpoulain]

You probably need to configure Symfony as well: https://symfony.com/blog/new-in-symfony-5-4-language-negotiation.

[bpolaszek]

Oh, didn't know about this one.

Unfortunately, it still doesn't work either. Could it be related to the API-Platform version I'm using (2.6.8 - forgot to mention that earlier)?

[alanpoulain]

It should probably work if you are using the right Symfony version.

[bpolaszek]

I actually do (5.4.17). 🤷

Will dig further and post updates here for the records, thanks for your precious help. 🙏

[norkunas]

except I cannot easily access the variable(s) that triggered the violation (here: max with a value of 10).

As a workaround to avoid customizing serialization you could set your max also in payload option and access it, just configure api_platform.validator. serialize_payload_fields: ~ option to expose it

[bpolaszek]

That's what I tried at first but it didn't work.

api_platform:
    validator:
        serialize_payload_fields:
            - max
            - limit

Same response produced as above.

[norkunas]

Did you define max on Assert\Count payload? Meaning Assert\Count(max: 10, payload: ['max' => 10])

[bpolaszek]

Oh, no I didn't - I thought values would be bound directly.

It works now! I'll probably use that if I don't manage to use @alanpoulain's solution (which would be way easier, actually...).

Thanks!
Ben