NullBooleanField returns boolean value False for empty QueryDict.

[cosmosgenius]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

Create a serializer as below with the test data

from django.http import QueryDict
from rest_framework import serializers

class TestSerializer(serializers.Serializer):
    is_active = serializers.NullBooleanField(required=False)

s_dict = TestSerializer(data={})
s_dict.is_valid()

s_qdict = TestSerializer(data=QueryDict())
s_qdict.is_valid()

Expected behavior

s_dict and s_qdict has the same value which is is_active: None

Actual behavior

s_dict returns is_active: None but s_qdict returns is_active: False

NullBooleanField was primarily used to avoid default_empty_html from BooleanField. Now that it is merged what is the alternative?

[amikrop]

I observe that https://github.com/encode/django-rest-framework/blob/master/rest_framework/fields.py#L432 is False for the first case (data={}) which raises SkipField here https://github.com/encode/django-rest-framework/blob/master/rest_framework/serializers.py#L476 and True for the second case (data=QueryDict()) which lets set_value to be called here https://github.com/encode/django-rest-framework/blob/master/rest_framework/serializers.py#L486
That is the difference between those 2 cases, which causes this, but I don't know if this is intended behavior or not.

[xordoquy]

This is likely because NullBooleanField doesn't override the BooleanField's default_empty_html value which is False.

If you alter your field definition as is_active = serializers.NullBooleanField(required=False, default=None) you'll get a consistent behaviour.

A PR with the appropriate test could fix that too.

[amikrop]

That's right, are we sure though that the developers' intentions are for NullBooleanField's default_empty_html to be None?
If yes, we can make that small PR, should be trivial.

[cosmosgenius]

That's right, are we sure though that the developers' intentions are for NullBooleanField's default_empty_html to be None?
If yes, we can make that small PR, should be trivial.

Yes that is the expectation. But @xordoquy alternate field definition works well with BooleanField which is the right way to do since NullBooleanField is deprecated.

This does feel like a breaking change though in my opinion. If we didn't have proper CI/CD tests, this won't have been caught.

[beesnotincluded]

We too were caught out by this change. Our CI/CD test noticed the regression and we spent quite a while getting to the bottom of it.

[jaredmcdonald]

Just ran across this when upgrading our project to to 3.12.x (from 3.11.x) and also only caught it because of tests.

A BooleanField with default=None is still a bit of a departure from the previous behavior, where e.g. in @cosmosgenius' example above, is_active would not be present in validated_data if it wasn't passed in at all in the QueryDict. Is there some reason that the key should be present?

[Safrone]

I faced this as well where I was expecting the empty query dict to not insert the boolean

seeing that NullBooleanField is deprecated for DRF and django and I didn't actually need the third state (just using it to know whether true or false was explicitly given since default_empty_html otherwise obfuscates that), my solution is to override BooleanField:

from rest_framework import fields, serializers

class DefaultEmptyBooleanField(fields.BooleanField):
    default_empty_html = fields.empty

class MySerializer(serializers.Serializer):
    boolean_field = DefaultEmptyBooleanField(required=False)

use case:

from django.http import QueryDict

serializer = MySerializer(data=QueryDict(''))
serializer.is_valid()
serializer.validated_data # OrderedDict()

serializer = MySerializer(data=QueryDict('boolean_field=true'))
serializer.is_valid()
serializer.validated_data # OrderedDict([('boolean_field', True)])

You can add allow_null=True to DefaultEmptyBooleanField() for the added null option

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[auvipy]

can any of you try #8614 and report back please? seems related to this issue