UserWarning occurs when using None | str as type in dataclass and using scheam.load().

[yuji38kwmt]

Environment

• Python 3.11.2
• dataclasses-json 0.5.7

What's happen?

When I exected the following python file, UserWarning occurred.

from dataclasses import dataclass
from dataclasses_json import DataClassJsonMixin


@dataclass(frozen=True)
class Project(DataClassJsonMixin):
    project_id: str
    project_name: None | str = None


print("Use `Project.from_dict()`")
print(Project.from_dict({"project_id": "1"}))
print("Use `Project.schema().load()`")
print(Project.schema().load([{"project_id": "2"}], many=True))

$ python sample1.py 
Use `Project.from_dict()`
Project(project_id='1', project_name=None)
Use `Project.schema().load()`
/home/vagrant/.pyenv/versions/3.11.2/lib/python3.11/site-packages/dataclasses_json/mm.py:271: UserWarning: Unknown type <class 'NoneType'> at Project.project_name: None | str It's advised to pass the correct marshmallow type to `mm_field`.
  warnings.warn(
[Project(project_id='2', project_name=None)]

However I changed project_name's type from None | str to Optional[str], UserWarning did not occurre.

from dataclasses import dataclass
from dataclasses_json import DataClassJsonMixin
from typing import Optional


@dataclass(frozen=True)
class Project(DataClassJsonMixin):
    project_id: str
    project_name: Optional[str] = None


print("Use `Project.from_dict()`")
print(Project.from_dict({"project_id": "1"}))
print("Use `Project.schema().load()`")
print(Project.schema().load([{"project_id": "2"}], many=True))

What do I expect ?

I expect that even if I use None | str instead of Optional[str], the UserWarning should not occur. Both None | str and Optional[str] have the same meaning.

Supplementary

Related to https://qiita.com/yuji38kwmt/items/85a8bd836f06f3df8321 .

[george-zubrienko]

I see according to PEP they are indeed equivalent, I'll take a look at this

https://peps.python.org/pep-0604/

[george-zubrienko]

Alright I think problem is with typing-inspect lib, which we should really just replace as this one is really aimed at typing module, while the pipe overload is not coming from there.

I'll prepare a PR this week and create a follow-up to replace that lib.

[george-zubrienko]

Alright partially correcting myself here, issue is really much more simple than that. Linking a PR that should fix it :)