A quick review of `tyro`, a CLI library.

I recently discovered https://brentyi.github.io/tyro/ I've used `typer` for many years, so much that I wrote a band-aid project to fix up some of its feature deficiencies: https://pypi.org/project/dtyper/ I never used `click` but it apparently provides a full-featured CLI platform. `typer` was written on top of `click` to use Python type annotations on functions to automatically create the CLI. And it was a revolution when it came out - it made so much sense to use the same mechanism for both purposes. However, the fact that `typer` built around a function call means that the state that it delivers to you is a lot of parameters in a flat scope. Many real-world CLIs have dozens or even hundreds of parameters that can be set from the command line, so this rapidly becomes unwieldy. My `dtyper` helped a bit by allowing you to use a `dataclass`, and fixed a couple of other issues, but it was artificial, worked only on `dataclass` and none of the other data class types, and had only one level, and was incorrectly typed. (It spun off work I was doing elsewhere, it was very useful to me at the time.) `tyro` seems to fix all of the issues. It lets you use functions, almost any sort of data class, nested data classes, even constructors to automatically build a CLI. So far my one complaint is that the simplest possible CLI, [a command that takes zero or more filenames, is obscure](https://github.com/brentyi/tyro/issues/439). But I found the way to do it neatly, it's more a documentation issue. Looking at some of my old projects, there would have been whole chunks of code which would never have been written, passing command line flags down to sub-objects. (No, I won't rewrite them, they work fine.) Verdict: so far so good. If it continues to work as advertised I'll probably use it in new development.