Fields with source from related model not inheriting model field properties

[mschoettle]

I just realized that when using a ModelSerializer and adding additional fields from related models directly as fields by specifying the source argument on a field, the field does not inherit the field properties as regular fields for models do.

For example

class Foo(models.Model):
    some_field = models.CharField(max_length=100)
    bar = models.ForeignKey(to=Bar)

class FooSerializer(serializers.ModelSerializer):
    bar_field = CharField(source='bar.bar_field')

    class Meta:
        model = Foo
        fields = ['id', 'some_field', 'bar_field']

The serializer field for some_field has max_length=100 whereas bar_field does not "inherit" the properties from Bar.bar_field.

I understand that the intended way is to use a nested serializer. I am wondering though if there is a way to achieve this with fields specifying the source argument.

[browniebroke]

You can use the extra_kwargs option:

class FooSerializer(serializers.ModelSerializer):
    class Meta:
        model = Foo
        fields = ['id', 'some_field', 'bar_field']
        extra_kwargs = {'bar_field': {'source': 'bar.bar_field'}}