Bug(?): FBT001 for a dataclass

[Spectre5]

In the __post_init__ method of a dataclass, the InitVar's cannot be passed by keyword argument, they must be positional. But in this case, FBT001 is trigged. For example:

from dataclasses import dataclass, InitVar

@dataclass
class Fit:
    force: InitVar[bool] = False

    def __post_init__(self, force: bool) -> None:
        print(force)

Fit(force=True)

And then with Ruff:

$ ruff --version
ruff 0.2.1
$ ruff check --isolated --select=FBT test.py 
test.py:7:29: FBT001 Boolean-typed positional argument in function definition
Found 1 error.

If we instead change the definition to def __post_init__(self, *, force: bool) -> None:, then FBT001 is no longer triggered, but the code will not work:

$ python test.py 
Traceback (most recent call last):
  File "<snip>/test.py", line 11, in <module>
    Fit(True)
  File "<string>", line 3, in __init__
TypeError: Fit.__post_init__() takes 1 positional argument but 2 were given

I suggest that dataclasses __post_init__ be added to an internal whitelist to be ignored by FBT001.

[charliermarsh]

👍 We should allow this.