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Union[Literal, ...] is unusable #322
Description
To Reproduce
from dataclasses import dataclass
from typing import Literal, Union
import simple_parsing
@dataclass
class Foo:
bar: Union[Literal["a"], dict] = "a"
parser = simple_parsing.ArgumentParser()
parser.add_arguments(
Foo,
dest="foo",
default=Foo(),
)
parser.parse_args()Expected behavior
The code should run, just like it does if I replace Union[Literal["a"], dict] with Literal["a"]
Actual behavior
$ python issue.py
Couldn't parse value a, returning the value as-is. (exceptions: [TypeError('Cannot instantiate typing.Literal'), ValueError('dictionary update sequence element #0 has length 1; 2 is required')])
usage: test.py [-h] [--bar Literal|dict]
test.py: error: argument --bar: invalid Literal|dict value: 'a'Desktop (please complete the following information):
- simple-parsing = "^0.1.5"
- Python version: 3.11
Reacted by Flávio Lisbôa and Julian Lemmel
Activity
Revert "Adjust multifun"
Add test to repro #322
Attempt to work around lebrice/SimpleParsing#322
FranzKnut commentedon Jul 20, 2026
This issue is still unresolved, right?
lebrice commentedon Jul 27, 2026
Hi @FranzKnut , indeed I think this might have slipped my mind. There is a draft PR with a fix for this, (#325) I'll see if I can update it and merge it soon. Thanks for the reminder! :)
Merge origin/master and fix #322 (Union[Literal, ...] parsing)
Fix lebrice#322 (Union[Literal, ...]) (lebrice#325)