Attrs default factory is not used by default

[bilelomrani1]

🐛 Bug report

When using a factory to build a default value in a attrs dataclass, jsonargparse ignores the factory at configuration time and considers the field as empty.

To reproduce

from typing import List

from attrs import define, field
from jsonargparse import ArgumentParser


@define
class Configuration:
    name: List[str] = field(factory=lambda: ["hello", "world"])


if __name__ == "__main__":
    parser = ArgumentParser()
    parser.add_argument("--data", type=Configuration)
    cfg = parser.parse_args()
    print(parser.instantiate_classes(cfg))

$ python main.py
usage: main.py [-h] [--data CONFIG] [--data.name NAME]
main.py: error: Configuration check failed :: Parser key "data.name":
  Expected a <class 'list'>. Got value: _Nothing.NOTHING

Expected behavior

The default factory should be called and the following should be printed to stdout:

$ python main.py
Namespace(data=Configuration(name=['hello', 'world']))

Environment

• jsonargparse version: 4.21.2
• Python version: 3.10.9
• How jsonargparse was installed: pip install jsonargparse
• OS: MacOS 13.2.1

[mauvilsa]

Thank you very much for reporting! Good to know that there is interest for the attrs support. The field factory should be an easy fix. Will do it soon.

[mauvilsa]

@bilelomrani1 I have implemented a fix #303. You can try it out by installing as:

pip install "jsonargparse @ https://github.com/omni-us/jsonargparse/zipball/issue-299-attrs-field-factory"

[bilelomrani1]

Hi @mauvilsa, it works perfectly thank you very much.