Alternative syntax for unions requires Python 3.10 or newer

[stolenzc]

Envirement data

• pylance version: 2020.10.2
• vscode version: 1.50.1
• python version: 3.8.5
• Djagno version: 3.0.3
• OS platform: MacOs 10.15.7

My django program also alert this and I don't know why, I want to know why and how to ignore this warning?

[Zajozor]

Experiencing the same issue, pylance version: 2020.10.2 (pyright d6db7c90), Python 3.7, Django 2.2

Same as the op, we are using Django Rest Framework.

The permission classes which contain the | between them inherit from this class

@six.add_metaclass(BasePermissionMetaclass)
class BasePermission(object):
    """
    A base class from which all permission classes should inherit.
    """

    def has_permission(self, request, view):
        """
        Return `True` if permission is granted, `False` otherwise.
        """
        return True

    def has_object_permission(self, request, view, obj):
        """
        Return `True` if permission is granted, `False` otherwise.
        """
        return True

Further related code can be found at https://github.com/encode/django-rest-framework/blob/master/rest_framework/permissions.py#L97 and near that.

Even manually adding a metaclass with defined __or__ property to the Permission classes does not remove the pylance error. Please let me know if further information is required.

[erictraut]

Thanks for the bug report. I've updated the logic so it detects the case where a class has a custom metaclass that supports the __or__ or __ror__ method and use that for the | operator rather than assuming a misuse of of PEP 614 prior to Python 3.10. This fix will be in the next version of pylance.

[cdce8p]

@erictraut The | operator for type annotations won't be exclusive to 3.10, since postponed evaluation of annotations is enough to support it, as long as the type checker understands it. It can even be used in type comments with Python 2. python/typing#429 (comment) and python/mypy#9647

It might be an idea to limit the warning to isinstance and issubclass calls, or check if from __future__ import annotations is used with type annotations.

[erictraut]

@cdce8p, that's a good point. I've changed the code to suppress that error in any situation where the evaluation of the type annotation is postponed (within quotes and with from __future__ import annotations enabled). The diagnostic will still be reported in cases where you're using <3.10 and the evaluation is not postponed (e.g. in a type alias declaration or an isinstance call).

[jakebailey]

This issue has been fixed in version 2020.10.3, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/master/CHANGELOG.md#2020103-28-october-2020

[Zajozor]

@jakebailey The problem is not fixed in 2020.10.3

[Info  - 9:19:46 AM] Pylance language server 2020.10.3 (pyright b881f28d) starting

The specific class is from DRF ( details in my comment above ).

Should I create a new issue, or can we reopen this?
Thank you.

[cdce8p]

Same with type annotations. It seems mostly fixed, however I'm encountering a wired edge case with . notation.
E.g. time | None works, whereas dt.time | None dosen't.