Error when parsing config file with type=Path

[alealv]

How to reproduce

from jsonargparse import ArgumentParser
from pathlib import Path

parser = ArgumentParser()
parser.add_argument("--path", type=Path)
parser.parse_args(["--path", "any/path"])

Error

test.py: error: Parser key "output_dir": not enough values to unpack (expected 2, got 1)

Version

➜ pip list | grep jsonarg
jsonargparse                       3.19.3

Tracing

The error fails here and it's called from here.

[mauvilsa]

Thank you for reporting!

Note that pathlib.Path is not supported as a core type. What is happening when you add an argument with type=Path is that it creates a subclass argument, see https://jsonargparse.readthedocs.io/en/stable/#class-type-and-sub-classes. The not enough values to unpack error is a bug since it should be giving the same error as if you did parser.parse_args(["--path", "any/path.ext"]). Will look at this.

Also note that jsonargparse has specific types for checking paths, see https://jsonargparse.readthedocs.io/en/stable/#parsing-paths. If you specifically want pathlib.Path as a core type, then you can register it, see https://jsonargparse.readthedocs.io/en/stable/#registering-types.

from jsonargparse.typing import register_type
from pathlib import Path
register_type(Path, type_check=lambda v, t: isinstance(v, t))

[mauvilsa]

Even though pathlib.Path can be registered, it is not very useful. The issue is that pathlib.Path accepts any string, thus no validation and the point of the parser is that values are validated and fail if invalid. That is why there are path types in jsonargparse which do validation.

[alealv]

Thanks for the explanation.

I noticed that jsonargparse has specific Path type checking but I just wanted to have an object of type pathlib.Path and do the validation or dir creation afterward in the code.