Queryset argument is ignored on reverse related fields

[pawelad]

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

I believe that the queryset argument on reverse relationships is ignored.

class Competition(models.Model):
    active = models.BooleanField(verbose_name="active")

class Season(models.Model):
    competition = models.ForeignKey(
        verbose_name="competition",
        to=Competition,
        related_name="seasons",
        on_delete=models.PROTECT,
    )


class CompetitionSerializer(serializers.ModelSerializer):
    seasons = serializers.PrimaryKeyRelatedField(
        queryset=Season.objects.filter(active=True),
        many=True,
    )

    class Meta:
        model = Competition
        fields = ["id", "seasons"]

Expected behavior

I'd expect the CompetitionSerializer.seasons to only include linked seasons that have active set to True.

Actual behavior

I get all the linked seasons.

More importantly, using something like queryset="foobar" doesn't result in an error and still returns all linked seasons.

[pawelad]

I'm using this as a workaround, but it's very non-ideal because of the number of needed SQL queries:

    seasons = serializers.SerializerMethodField()

    def get_seasons(self, obj):
        return Season.objects.filter(competition_id=obj.id, active=True).values_list("id", flat=True)

[pawelad]

After more debugging and digging in, this is probably (and unfortunately) a duplicate of #1228

[no-dap]

Guess this is an usage question.

[pawelad]

And the actual long term solution I found that ticks all the boxes:

class CompetitionViewSet(viewsets.ModelViewSet):
    queryset = Competition.objects.prefetch_related(
        Prefetch('seasons', queryset=Season.objects.filter(active=True))
    )

Source: https://stackoverflow.com/a/55315566/3023841

Do you guys think it would be worth it to update the docs to say:

• queryset argument is ignored on reverse relationships
• the above is the suggested way of filtering reverse relationships

I can try and do the PR.

[no-dap]

As docs said, queryset argument used for model instance lookups when validating the field input, not for filtering.
Wouldn't this change makes people confused?
I think this is just a good stackoverflow answer, not a good documentation :)

[pawelad]

I think this kinda of question comes up quite often so could be touched on in the docs more, but I absolutely understand your point.

Thanks for chiming in, I appreciate it a lot!