[Feature request] Use `typing.Annotated` to redefine field types about djangorestframework-dataclasses

[oxan]

Without checking for Annotated types, I got this error:

I don't think this has anything to do with Annotated types, but instead with InMemoryUploadedFile not being a recognized type. Something like Annotated[int] should work fine already.

I was wondering if it's possible to implement discovery of fields from Annotated[...] on your side.

It's certainly possible, but I think the more important question is whether it's desirable. There's already support for specifying the serializer field type in the dataclass definition like this:

@dataclass
class UploadDocumentRequest:
    file: InMemoryUploadedFile = dataclasses.field(metadata={'serializer_field': fields.FileField()})

I suppose it's a bit more verbose, but it's also more generic: you can also add a serializer_kwargs key in the metadata to specify any arguments for the serializer field, which is harder to do with type annotations. If the verbosity bothers you, it's also possible to define a simple helper function to abbreviate it.

[MaksimZayats]

you can also add a serializer_kwargs key in the metadata to specify any arguments for the serializer field, which is harder to do with type annotations.

It is also possible with Annotated because it's not an annotation, but an instance of the field itself:

@dataclasses.dataclass
class Person:
    # email: str = dataclasses.field(metadata={'serializer_field': fields.EmailField()})
    email: Annotated[str, fields.EmailField()]
 
    # age: int = dataclasses.field(metadata={'serializer_kwargs': {'min_value': 0}})
    age: Annotated[int, fields.IntegerField(min_value=0)]

[oxan]

It is also possible with Annotated because it's not an annotation, but an instance of the field itself:

Ah yeah, that's true, though it's a bit more limited, as it requires you to specify all the required arguments of the field, instead of just the ones you want to override. My point remains standing though, we already have a way to override fields within the dataclass declaration, and I don't see a good reason to add another one (yet).

[MaksimZayats]

I don't see a good reason to add another one (yet).

In my case, I have a common type that used between couple serializers:

DocumentsType: TypeAlias = Annotated[
    list[models.Document],
    PrimaryKeyRelatedField(
        queryset=models.Document.objects.filter(deleted_at=None),
        many=True,
    ),
]

@dataclass
class A:
    documents: DocumentsType

@dataclass
class B:
    documents: DocumentsType