The `choices` parameter of `add_argument()` is not functioning correctly.

[Rustam Khadipash]

🐛 Bug report

To reproduce

from jsonargparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument("--mode", type=int, default=1, choices=[0, 1])
cfg = parser.parse_args()

print(cfg.mode)

Output:

> python argparse_test.py --mode 1
usage: argparse_test.py [-h] [--mode {0,1}]
argparse_test.py: error: argument --mode: invalid choice: '1' (choose from 0, 1)

Expected behavior

Aligned with argparse.

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("--mode", type=int, default=1, choices=[0, 1])
cfg = parser.parse_args()

print(cfg.mode)

Output:

> python argparse_test.py --mode 1
1

Environment

• jsonargparse version (e.g., 4.8.0): 4.27.1
• Python version (e.g., 3.9): 3.8.17
• How jsonargparse was installed (e.g. pip install jsonargparse[all]): pip install jsonargparse[signatures,omegaconf,urls]>=4.25.0
• OS (e.g., Linux): Ubuntu 20.04.5 LTS

[Mauricio Villegas]

Thank you for reporting! As an update. I looked at this some time ago, and it seems to require quite a complex change to fix. Unfortunately this relates to the fact that argparse wasn't really designed for extending as much as it has been done here. A fundamental change in the core implementation is required. I am not saying it won't be fixed, but very likely it will take time.

For the time being, as a workaround, consider using an Enum as a type.