I have a snippet below which runs fine on python 3.7.0 but raises a ValueError exception on 3.7.1. I believe it's related to https://bugs.python.org/issue33805.

The error: c:\python\lib\dataclasses.py:1219: ValueError

The script:

from dataclasses import replace, dataclass, InitVar

@dataclass
class Test:
    a:int = 1
    b:InitVar[int] = None

    def __post_init__(self, b):
        if b is not None:
            self.a = b


if __name__ == '__main__':
    t = Test()
    t1 = Test(b=5)
    assert t1.a == 5

    t2 = replace(t1, **{})
    print(t2)

Fixed title

any updates on this? Would be great if any of the two candidate PRs was merged. It's basically impossible to use replace() with default InitVars..
Thank you in advace

New changeset 75220674c07abfc90c2cd7862d04cfa2e2354450 by Zackery Spytz in branch 'master':
bpo-36470: Allow dataclasses.replace() to handle InitVars with default values (GH-20867)
https://github.com/python/cpython/commit/75220674c07abfc90c2cd7862d04cfa2e2354450

New changeset bdee2a389e4b10e1c0ab65bbd4fd03defe7b2837 by Miss Islington (bot) in branch '3.8':
bpo-36470: Allow dataclasses.replace() to handle InitVars with default values (GH-20867) (GH-25201)
https://github.com/python/cpython/commit/bdee2a389e4b10e1c0ab65bbd4fd03defe7b2837

New changeset 013c30e5fcee449cee63354d34585d6111782c82 by Miss Islington (bot) in branch '3.9':
bpo-36470: Allow dataclasses.replace() to handle InitVars with default values (GH-20867) (GH-25200)
https://github.com/python/cpython/commit/013c30e5fcee449cee63354d34585d6111782c82

Thanks for the fix!