Is this an issue with PySide6 or Pyright?

[mmerlo]

I ran across this false negative and I'm not sure if this is an issue with PySide6 (6.8.0) or Pyright. Below is an example where I expect a type error at self.b.write_bytes(data) in the write_float method, but no error is reported. If @Slot(bytes) is removed in BytesObject, Pyright correctly detects the typing error.

Is this an issue with PySide6 or Pyright?

from PySide6.QtCore import QObject, Slot


class FloatObject(QObject):
    def __init__(self):
        super().__init__()
        self.b = BytesObject()

    def write_float(self, data: float):
        self.b.write_bytes(data)  # expect type error here


class BytesObject(QObject):
    @Slot(bytes)  # removing this line will trigger type error
    def write_bytes(self, data: bytes):
        pass

[erictraut]

When I install the latest version of Pyside6 (6.8.1.1), pyright gives me a type checking error in the code above:

Argument of type "(self: Self@BytesObject, data: bytes) -> None" cannot be assigned to parameter "function" of type "(Any) -> Any" in function "__call__"
  Type "(self: Self@BytesObject, data: bytes) -> None" is not assignable to type "(Any) -> Any"
    Extra parameter "data"

Are you seeing this error?

[mmerlo]

Yes, I see that error with Pyside6 (6.8.1.1).

That error started when I upgraded from Pyside6 (6.8.0). I could not figure out how to define a slot with an argument in 6.8.1.1 without Pyright giving a typing error so I downgraded to 6.8.0 with the assumption that 6.8.1.1 had a regression in type hinting.

Is the false negative in 6.8.0 and the type error you're pointing out in 6.8.1.1 related?

[erictraut]

Pyside6 6.8.0 wouldn't install for me. It appears it's not compatible with Python 3.13. I was able to get it to install by reverting to an older version of Python.

The Pyside6 6.8.0 library defines the Slots class in a way that obscures all type information if you apply the class as a decorator. That's why you're not seeing an type error here. This isn't a bug in pyright; it's arguably a bug in the library's type annotations. And it appears that it has been fixed in a later version (6.8.1.1).

[mmerlo]

Thanks. As it stands, I do not know how to define the @Slot() decorator for write_bytes without getting a typing error (in 6.8.1.1). It helps to know that this is not a bug with Pyright. At worst, I'll just use # type: ignore for that line.

[erictraut]

I don't know anything about Pyside6, so you I'm not able to help you there. You could maybe post a question to the maintainers of that library and get their advice.

[mmerlo]

Sounds good. Thanks.

[mmerlo]

Update: This is a known issue with Pyside 6.8.1 - PYSIDE-2942

PYSIDE-2977 is a duplicate issue that I find more concise.