Add multilevel subcommands support to CLI

[rusmux]

🚀 Feature request

Currently jsonargparse.CLI can handle only one level of subcommands through classes. For example:

from jsonargparse import CLI

class mycli:
    @staticmethod
    def subcommand1(): ...


if __name__ == "__main__":
    CLI(components=[mycli])

But there is no easy way to add more subcommands, since embedding a class in another one will cause an error.:

from jsonargparse import CLI

class mycli:
    @staticmethod
    def subcommand1(): ...

    class subcommand2:
        @staticmethod
        def subsubcommand1(): ...


if __name__ == "__main__":
    CLI(components=[mycli])

ValueError: Invalid or unsupported input: class=<class '__main__.mycli'>, method_or_property=subcommand2

To add more subcommands, you need to use jsonargparse.ArgumentParser and implement all the logic manually.

Motivation

It would be great to be able to create multilevel subcommands easily.

Pitch

Add multilevel subcommands support to jsonargparse.CLI.

Alternatives

[mauvilsa]

A clarification. Two levels of subcommands is currently possible by having multiple classes. For example:

from jsonargparse import CLI

class level1_cmd_a:
    @staticmethod
    def level2_cmd_x(): ...

class level1_cmd_b:
    @staticmethod
    def level2_cmd_y(): ...

if __name__ == "__main__":
    CLI(components=[level1_cmd_a, level1_cmd_b])

Though, easier ways to implement can be added. For example similar to fire.Fire(<dict>). Two levels of subcommands could be defined as:

{
    "level1_cmd_a": {
        "level2_cmd_x": func_x,
    },
    "level1_cmd_b": {
        "level2_cmd_y": func_y,
    }
}

[rusmux]

Oh, yes, I missed it, thank you! But how to add more levels? The fire way of doing this seems nice.

[mauvilsa]

More than two levels currently is only possible by manually creating the ArgumentParser.

[rusmux]

Would it be possible to support fire-like dictionaries in the future?

[mauvilsa]

Yes.

[rusmux]

Thank you, will look forward to it!

[mauvilsa]

@rusmux @Borda I created a pull request (#346) that implements CLI subcommands via a dict. Please try it out.