Intended way to define a mutually exclusive group inside a normal argument group with `with_annotated`

[neoniobium]

Question, Bug report or Feature Request

Is there an intended way to define a mutually exclusive argument group inside a normal argument group when using the with_annotated decorator?

I think this is supported by builtin argparse, while nested argument groups and normal argument groups inside mutually exclusive argument groups are not supported at least since Python 3.11. See argparse

[KelvinChung2000]

My current thinking is to keep supporting it and align it with argparse. However, I also think we should ban it, since this is never the intended use case for argparse. What is your thought @tleonhardt ?

[tleonhardt]

I'd say as long as we have a way of supporting a mutually exclusive group I think that is fine. I don't see the need to support a mutually exclusive group inside a normal argument group. But perhaps I am missing something?

[neoniobium]

I think this is the intended way to use a mutually exclusive group. This example is taken directly from the argparse documentation.

parser = argparse.ArgumentParser(prog='PROG')
group = parser.add_argument_group('Group title', 'Group description')
exclusive_group = group.add_mutually_exclusive_group(required=True)
exclusive_group.add_argument('--foo', help='foo help')
exclusive_group.add_argument('--bar', help='bar help')
parser.print_help()

[KelvinChung2000]

For your specific example, you can do it in the following way

from typing import Annotated

import cmd2
from cmd2.annotated import Group, Option, with_annotated


class App(cmd2.Cmd):
  @with_annotated(
      mutually_exclusive_groups=(Group("foo", "bar", required=True, title="Group title", description="Group description"),),
  )
  def do_prog(
      self,
      foo: Annotated[str | None, Option(help_text="foo help")] = None,
      bar: Annotated[str | None, Option(help_text="bar help")] = None,
  ) -> None:
      self.poutput(f"foo={foo} bar={bar}")


if __name__ == "__main__":
  App().cmdloop()

[KelvinChung2000]

I just noticed the title and description are not propagating to the help correctly. I will have this fixed.

[neoniobium]

To my understanding, argparse is intended to support any number of arguments and/or mutually exclusive groups within an argument group. This makes sense to me: normal argument groups label arguments, while mutually exclusive groups change the behavior of the parser.