Subparsing issue with Union types

[pculbertson]

Hi Brent,

We hit another issue with some nested configs we're using -- basically something is going awry (I think) due to a type Union.

Here's a MWE:

import dataclasses
import dcargs

from typing import Tuple, Union

@dataclasses.dataclass(frozen=True)
class Subtype:
    data: int = 1
    
@dataclasses.dataclass(frozen=True)
class TypeA:
    subtype: Subtype = Subtype(1)

@dataclasses.dataclass(frozen=True)
class TypeB:
    subtype: Subtype = Subtype(2)
    
@dataclasses.dataclass(frozen=True)
class Wrapper:
    supertype: Union[TypeA, TypeB] = TypeA()
    
if __name__ == "__main__":
    wrapper = dcargs.cli(Wrapper) # errors when running with supertype:type-a
    print(wrapper)

If you put this in a module subparsers.py and run $ python subparsers.py, everything works; if you run $ python subparsers.py supertype:type-a, it throws the following error:

File "/opt/conda/lib/python3.7/site-packages/dcargs/_cli.py", line 272, in _cli_impl
    avoid_subparsers=avoid_subparsers,
  File "/opt/conda/lib/python3.7/site-packages/dcargs/_calling.py", line 169, in call_from_args
    avoid_subparsers=avoid_subparsers,
  File "/opt/conda/lib/python3.7/site-packages/dcargs/_calling.py", line 117, in call_from_args
    assert len(parser_definition.subparsers_from_name) > 0
AssertionError

Thanks again for the great package + sorry to raise obscure issues! No problem if this isn't high-priority.

[brentyi]

Thanks for the detailed reproduction instructions!!

This was actually already fixed in a different branch, I just pulled the changes into master and did a release. Should be resolved now. 🙂