Handling field names that conflict with serializer attributes?

[Kangaroux]

I have a data structure I need to validate which has a field called label. However, serializers have an attribute on them called label. Trying to set the field is overwriting the attribute which mypy (correctly) complains about:

class FooSerializer(serializers.Serializer):
    # Error: Incompatible types in assignment (expression has type "CharField", 
    # base class "Field" defined the type as "Optional[str]")  [assignment] mypy
    label = serializers.CharField(max_length=10)

I can rename the field and change the source so that it will serialize the object correctly:

label_ = serializers.CharField(max_length=10, source="label")

However, the source argument only affects serializing, not deserializing:

>>> s = FooSerializer(data={"label": "test"})
>>> s.is_valid()
False
>>> s.errors
{'label_': [ErrorDetail(string='This field is required.', code='required')]}

Is it possible to do this without hacking together something in an override?

[TauPan]

Hi!

This is an old question, but I found this while looking for answers to my problem, so I'll add this for posterity. (Because of Wisdom of the Ancients)

I had a similar problem in my code recently. My model has a JSONField called data which is also a property on the serializer class and object. (The distinction between object and class is important in this case.)

This works fine in practice, since DRF moves all Fields in the object to _declared_fields so the serializer object still has data as a property, while the declared field lives in _declared_fields on the object. Of course neither mypy nor pyright can grok this.

What I did was to declare the field as a field, which satisfies both mypy and pyright:

data: serializers.Field = JSONField(required=False)

In the OP's case the following should help:

class FooSerializer(serializers.Serializer):
    # All serializer Fields are moved into _declared_fields when the
    # metaclass creates the Serializer object, but the type checker
    # will think that `data` is a property, because it is defined as
    # such, so we have to assure it, that, only in this subclass, it's
    # a field.
    label: serializers.Field = serializers.CharField(max_length=10)

Cheers!