Pyright: Support for type hinting non specific dataclasses

[roeap]

Is your feature request related to a problem? Please describe.
I wanted to type hint a class to only accept dataclasses as inputs. Searching a bit on the web I found a (at least to me) reasonable solution on StackOverflow based on defining a Protocol.

From the same author, there is also an open issue on mypy, which might give even more context.

from dataclasses import dataclass
from typing import Dict, Protocol


class IsDataclass(Protocol):
    # checking for this attribute seems to currently be
    # the most reliable way to ascertain that something is a dataclass
    __dataclass_fields__: Dict


def dataclass_only(x: IsDataclass):
    ...  # do something that only makes sense with a dataclass


@dataclass
class A:
    pass


dataclass_only(A())  # a static type check should show that this line is fine

Describe the solution you'd like
Pyright should recognize that any class wrapped in @dataclass will support the above Protocol, and thus show that the last line is valid.

[erictraut]

Thanks for the suggestion. This will be implemented in the next published version of pyright.

[erictraut]

This is now implemented in version 1.1.33, which I just published.