Possible bug

[pySilver]

Hi!

Here is a possible bug: https://github.com/estebistec/drf-compound-fields/blob/master/drf_compound_fields/fields.py#L105

Shouldn't it be(?):

self.list_field = ListField(item_field, *args, **kwargs)

Otherwise validators may report required field error for some circumstances. Consider example:

myfield = ListOrItemField(IntegerField(), required=False, blank=True)

so, it woud result into:

[] -> Error myfield is required

[estebistec]

so in your example, a list value would be optional but an integer value would be required?

[pySilver]

@estebistec yeah well thats not clear from my example.

here is a serializer:

class MySerializer(Serializer):
    authors = ListOrItemField(
        PrimaryKeyRelatedField(
            queryset=Authors.objects.all(),
            error_messages={
                'does_not_exist': _(u"Invalid Account: %s")
            },
        ),
        write_only=True,
        required=False,
        blank=True
    )

So, since requred=False, authors field expected to accept empty values, such as empty list. Thats how DRF would behave. But in reality it would behave like DRF if empty value won't be passed by api client at all. Otherwise it would result in error:

{
    "authors": ['Field `authors` is required', ]
}

This is happening because undelying ListField did not receive _args and *_kwargs that were defined for original authors field, so it fails while validating field value at DRF side:

rest_framework.fields.WritableField#validate:

def validate(self, value):
        if value in validators.EMPTY_VALUES and self.required:
            raise ValidationError(self.error_messages['required'])

And this problem exists just for ListOrItemField, since ListField normally constructs field using _args and *_kwargs passed from serializer.

[estebistec]

Okay, I see. I'll poke at a fix this evening. Thanks for reporting it!

[estebistec]

Sorry, i haven't forgotten this. Simply passing args and kwargs didn't fix this like I'd hoped, so I have to dig deeper.

[pySilver]

Hm, that worked for me just fine. So passing empty list as value to a ListOrItemField did not result in required error. However passing an empty string would result in some other error – but this is how DRF work (and will work until 3.0)

[estebistec]

@pySilver have you moved to DRF 3.0 yet? I'm thinking of upgrading this lib for it and if you're game I would ensure this bug is fixed or not present in that upgrade.

[pySilver]

@estebistec nop, our app is too big to make an easy upgrade to 3.0 :/

[estebistec]

Please see #27