Is it possible to merge a Model/Form validator in Django-Rest-Framework?

Question

I've noticed that Django form and model validators should raise a django.core.exceptions.ValidationError, which is an immediate subclass of Exception.

In DRF, however, my validator is expected to raise rest_framework.exceptions.ValidationError, which is not a descendant of Django's (it derives from rest_framework.exceptions.APIException(Exception)).

Keeping myself DRY, how can I write a validator once, and use it in both, say, Django forms and a DRF serializer?

Here is a related question where DRF does not catch a Django core ValidationError

Answer 1

I'm using django==1.8 and DRF==3.3.2 and I've just written custom validator in my project and have noticed that both django.core and restframework's ValidationError exceptions works equally fine in DRF. I think this is due to this code in rest_framework.fields:

from django.core.exceptions import ValidationError as DjangoValidationError
from rest_framework.exceptions import ValidationError
...
def run_validators(self, value):
    """
    Test the given value against all the validators on the field,
    and either raise a `ValidationError` or simply return.
    """
    errors = []
    for validator in self.validators:
        if hasattr(validator, 'set_context'):
            validator.set_context(self)

        try:
            validator(value)
        except ValidationError as exc:
            # If the validation error contains a mapping of fields to
            # errors then simply raise it immediately rather than
            # attempting to accumulate a list of errors.
            if isinstance(exc.detail, dict):
                raise
            errors.extend(exc.detail)
        except DjangoValidationError as exc:
            errors.extend(exc.messages)
    if errors:
        raise ValidationError(errors)

As you can see, both exceptions can be caught by DRF, so you can use django.core.exceptions.ValidationError in both django forms and DRF.