I'm looking for a new CLI library. I like Click because it does very simple things very well. It gets hairy when you want to build more complex CLIs. For exa

I'm looking for a new CLI library. I like Click because it does very simple things very well. It gets hairy when you want to build more complex CLIs. For example, value options and validators don't play nicely because Click doesn't distinguish between the absence of a value and an invalid value, so you wind up dropping Click features and rewriting your own plumbing for that kind of stuff. The alternative is writing a more verbose CLI grammar, which leads to a really clunky UI.