simple foreign key assignment with serializers

[jerinpetergeorge]

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.)

Suppose we have two models,

class Musician(models.Model):
    name = models.CharField(max_length=50)

    def __str__(self):
        return f'{self.name}'


class Album(models.Model):
    artist = models.ForeignKey(Musician, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)

    def __str__(self):
        return f'{self.name} : {self.artist}'

and to create Album instance I have created a AlbumSerializer

class AlbumSerializer(serializers.ModelSerializer):
    class Meta:
        fields = '__all__'
        model = Album

and executed the code as

s = AlbumSerializer(data={'artist': 1, 'name': 'Foo'})
s.is_valid(True)
s.save()
print(s.data)
# {'id': 1, 'name': 'Foo', 'artist': 1}

This will return the PK of Musicians instance. But, many developers looking for an alternate solution which return a nested serializer response ( related SO post-DRF: Simple foreign key assignment with nested serializers? )

So, the common workaround to this problem is overriding the to_representation(...) method (of AlbumSerializer class). But, I there would be a DRF field which takes care of this situation.

Something like this will probably suite in the situation

from rest_framework import serializers


class PrimaryKeySerializerField(PrimaryKeyRelatedField):
    def __init__(self, serializer, **kwargs):
        self.serializer = serializer
        super().__init__(**kwargs)

    def use_pk_only_optimization(self):
        return False

    def to_representation(self, instance):
        return self.serializer(instance, context=self.context).data