`list[str]` does not accept integer arguments.

[kzrnm]

Consider the following arguments. When I pass 1 to a str argument, it is correctly read as '1', but when you pass it to list[str], it results in “Input should be a valid string.”

class RootCommand(
    BaseSettings,
    cli_parse_args=True,
    cli_implicit_flags='toggle',
):
    a: CliPositionalArg[str]
    rem: CliPositionalArg[list[str]] = Field(default_factory=list)
    text: str
    param: list[str] = Field(default_factory=list)

    def cli_cmd(self):
        print('------pydantic-settings-------')
        print(self)
        print('------pydantic-settings help-------')
        CliSettingsSource[argparse.ArgumentParser](RootCommand).root_parser.print_help()


def main(args: list[str] | None = None):
    CliApp.run(RootCommand, cli_args=args)


def mainA():
    print('------------argparse-------------')
    parser = argparse.ArgumentParser()
    parser.add_argument('a', type=str)
    parser.add_argument('rem', type=str, nargs='*')
    parser.add_argument('--text', type=str)
    parser.add_argument('--param', type=str, nargs='*')
    print(parser.parse_args())
    print('------------argparse help-------------')
    parser.print_help()


if __name__ == '__main__':
    mainA()
    print('----------------------------------')
    main()

$ python app.py 1 b c --text 2 --param e
------------argparse-------------
Namespace(a='1', rem=['b', 'c'], text='2', param=['e'])
------------argparse help-------------
usage: app.py [-h] [--text TEXT] [--param [PARAM ...]] a [rem ...]

positional arguments:
  a
  rem

options:
  -h, --help           show this help message and exit
  --text TEXT
  --param [PARAM ...]
----------------------------------
------pydantic-settings-------
a='1' rem=['b', 'c'] text='2' param=['e']
------pydantic-settings help-------
usage: app.py [-h] [--text str] [--param list[str]] A [REM ...]

positional arguments:
  A
  REM                (default factory: list)

options:
  -h, --help         show this help message and exit
  --text str         (required)
  --param list[str]  (default factory: list)

$ python app.py 1 0 c --text 2 --param 3
------------argparse-------------
Namespace(a='1', rem=['0', 'c'], text='2', param=['3'])
------------argparse help-------------
usage: app.py [-h] [--text TEXT] [--param [PARAM ...]] a [rem ...]

positional arguments:
  a
  rem

options:
  -h, --help           show this help message and exit
  --text TEXT
  --param [PARAM ...]
----------------------------------
Traceback (most recent call last):
  File "/home/kzrnm/workspace/forks/pydantic-settings/app.py", line 60, in <module>
    main()
  File "/home/kzrnm/workspace/forks/pydantic-settings/app.py", line 42, in main
    CliApp.run(RootCommand, cli_args=args)
  File "/home/kzrnm/workspace/forks/pydantic-settings/pydantic_settings/main.py", line 683, in run
    return CliApp._run_cli_cmd(model_cls(**model_init_data), cli_cmd_method_name, is_required=False)
  File "/home/kzrnm/workspace/forks/pydantic-settings/pydantic_settings/main.py", line 198, in __init__
    super().__init__(
  File "/home/kzrnm/workspace/forks/pydantic-settings/.venv/lib/python3.10/site-packages/pydantic/main.py", line 250, in __init__
    validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
pydantic_core._pydantic_core.ValidationError: 2 validation errors for RootCommand
rem.0
  Input should be a valid string [type=string_type, input_value=0, input_type=int]
    For further information visit https://errors.pydantic.dev/2.12/v/string_type
param.0
  Input should be a valid string [type=string_type, input_value=3, input_type=int]
    For further information visit https://errors.pydantic.dev/2.12/v/string_type

[hramezani]

Thanks @kzrnm for reporting this issue.

I can confirm the bug.

@kschwab Please take a look when you have time.

[kschwab]

@hramezani @kzrnm this is similar to #675, but specific to the CLI instead of ENV, where the CliSettingsSource would need to coerce types prior to handing them over to the EnvSettingsSource layer.

Currently, the CLI makes no effort to coerce types. It simply parses lists into a JSON string format internally. As an example, if we're more explicit with the zero type on the CLI, it will work (for pydantic settings):

$ python example.py 1 '"0"' c --text 2 --param e
------pydantic-settings-------
a='1' rem=['0', 'c'] text='2' param=['e']
------pydantic-settings help-------
usage: example.py [-h] [--text str] [--param list[str]] A [REM ...]

positional arguments:
  A
  REM                (default factory: list)

options:
  -h, --help         show this help message and exit
  --text str         (required)
  --param list[str]  (default factory: list)

i.e., JSON list parsing looks like:

• python example.py 1 '"0"' c --text 2 --param e --> '["0", "c"]'
• python example.py 1 0 c --text 2 --param e --> '[0, "c"]'

To resolve the above, CliSettingsSource would need to coerce the type based on the field type. I've tried to avoid coercion at the CLI level to let the ENV layer handle it, but the above would necessitate changing that.

@kzrnm also makes me think this will likely be related to some of the changes needed for #743.