Serializer incorrectly serializes Integer ArrayField as string

[Arthur Hanson]

If you define a model with an ArrayField of type Integer (PositiveSmallInteger, etc..) and use the built in serializer to json it will be serialized as an array of strings. Expected is that it will be serialized as an array of integers. For example, given the model below:

from django.db import models

# Create your models here.
from django.contrib.postgres.fields import ArrayField
from django.db import models

class Board(models.Model):
    pieces = ArrayField(
        base_field=models.PositiveSmallIntegerField()
    )

If you create an object with "pieces = [1, 3, 5, ]" and either create a fixture or call serialize directly you will get an array of strings. The following management command shows the issue:

from django.core.management.base import BaseCommand, CommandError
from serializertest.models import Board
from django.core.serializers import serialize
import json

class Command(BaseCommand):
    help = ''

    def handle(self, *args, **options):
        obj = Board.objects.first()
        if not obj:
            pieces = [1, 3, 5]
            obj = Board()
            obj.pieces = pieces
            obj.save()

        print(serialize('json', [obj]))
        print(json.dumps(obj.pieces))

Output will be:

[{"model": "serializertest.board", "pk": 1, "fields": {"pieces": "[\"1\", \"3\", \"5\"]"}}]
[1, 3, 5]

Note: the serialize output an array of strings, while calling json directly will give the expected array of integers.

[Arthur Hanson]

example model file with arrayfield

[Arthur Hanson]

management command that shows the issue

[Mariusz Felisiak]

Thanks for the report however (de-)serialization works for me with ArrayField(base_field=models.PositiveSmallIntegerField()). Are there any practical issues with the current approach (except for your preferences)? Other complex fields (such as JSONField) are also serialized as strings. I'm afraid that the proposed change is backward incompatible and you can always use a custom serializer, if you need a different format.

[Claude Paroz]

FWIW, I would be favorable to fix this, if not too complex to do.

[Mariusz Felisiak]

Replying to Claude Paroz:

FWIW, I would be favorable to fix this, if not too complex to do.

PoC is always welcome, I'm afraid that this will brake existing fixtures.

[Claude Paroz]

Arthur, would you like to work on a possible fix? (with no guarantee it will be accepted eventually)