ArrayField with JSONField and custom encoder raises error on serialization with "django.core.serializers.json".

[Anudeep Samaiya]

The encoder is not supported currently, which causes the serialization of uuid fields missing.

Current Implementation:

def value_to_string(self, obj):
    values = []
    vals = self.value_from_object(obj)
    base_field = self.base_field

    for val in vals:
        if val is None:
            values.append(None)
        else:
            obj = AttributeSetter(base_field.attname, val)
            values.append(base_field.value_to_string(obj))
    return json.dumps(values)

Suggested Implementation:

def value_to_string(self, obj, encoder=DjangoJSONEncoder):
    values = []
    vals = self.value_from_object(obj)
    base_field = self.base_field

    for val in vals:
        if val is None:
            values.append(None)
        else:
            obj = AttributeSetter(base_field.attname, val)
            values.append(base_field.value_to_string(obj))
    return json.dumps(values, cls=encoder)

How to reproduce:

import uuid
from django.contrib.postgres.fields import ArrayField, JSONField
from django.core.serializers.json import DjangoJSONEncoder

class Test(models.Model):
    uuid = models.UUIDField(unique=True, default=uuid.uuid4, editable=False)
    data = ArrayField(
        JSONField(encoder=DjangoJSONEncoder),
        max_length=200,
        blank=True,
        default=list,
    )

Now to test do the following:

from decimal import Decimal
from django.core import serializers
from test.models import Test

test = Test(data=[{'threshold_amount_usd': Decimal('0'), 'taint_percent_threshold': Decimal('0')}])
serializers.serialize("json", (test,))

test = Test(data=[{'id': uuid4()}])
serializers.serialize("json", (test,))

[Mariusz Felisiak]

Thanks for this report, however serialization works for me with:

• uuid = models.UUIDField(default=uuid.uuid4)
• array = ArrayField(models.UUIDField(), default=list)
• nested_array = ArrayField(ArrayField(models.UUIDField()), null=True)

I don't think you've explained the issue in enough detail to confirm a bug in Django. Please reopen the ticket if you can debug your issue and provide details about why and where Django is at fault. If you're having trouble understanding how Django works, see TicketClosingReasons/UseSupportChannels for ways to get help.

[Mariusz Felisiak]

Thanks for extra details. Unfortunately proposed change is backward incompatible, we also cannot fix this by changing to_python() and value_to_string() for JSONField (see discussions in ​PR9801, ​PR9809, and ​PR11538). JSONField can store JSON arrays so you should be able to use JSONField(encoder=DjangoJSONEncoder) instead of ArrayField(JSONField(encoder=DjangoJSONEncoder)). It also works with the db round-trip

>>> test = Test.objects.create(data=[{'id': uuid.uuid4()}])
>>> test.refresh_from_db()
>>> serializers.serialize('json', (test,))
'[{"model": "test_33086.test", "pk": 16, "fields": {"array": "[]", "nested_array": null, "data": "[{\\"id\\": \\"2a7cc8f4-a541-49ce-8310-c73c6cc2dc4c\\"}]"}}]'