Strange warning from PyCharm: Unexpected type(s): (Dict[str, String]) Possible type(s): (Union[SchemaABC, type, str, () -> SchemaABC]) (Union[SchemaABC, type, str, () -> SchemaABC])

I get this warning in PyCharm when using webargs to create a nested dictionary object:

data_args = {
    "name": fields.Nested(
        {"first": fields.Str(required=True), "last": fields.Str(required=True)}
    )
}

It happens for this line:

{"first": fields.Str(required=True), "last": fields.Str(required=True)}

Code is taken from the official webargs tutorial:

Why is PyCharm warning me about this and what should be the correct course of action?

[lafrech]

Yeah, we should remove Nested here but this requires bumping minimum marshmallow version, so I suppose it’ll wait until next major webargs version.

[sirosen]

In the past few days, marshmallow has done a release which should resolve this issue. You will need to ensure that pycharm (or any other type checker) is using the latest marshmallow version.

We also may have cleanup to do in webargs, but it should not impact users.