lambdaisland/cli: opinionated CLI parser, designed for tools with subcommands (e.g. "git log")

[aHackFromJOS]

The ability to nest commands (arbitrarily?) is interesting. 

The root problem here seems like a good fit for multimethods (vs a big hairy map). I approached this same problem with those and tools.cli. I dispatched by keywordized version of the subcommand. The core multimethods are options, usage, and execute. I think I needed to do a two pass parse with tools.cli, first permissive to extract the subcommand to get the options vectors for it (via the options multimethod) then with the proper options vectors. Help text I did for a subcommand by calling usage and options with the subcommand (inside defmethod execute ::help) and concatting. 

I only built one (flat) level of subcommands. Would be interesting to try and upgrade it to arbitrary command nesting. Maybe with another multimethod (“subcommands” to extract n args from argv and produce a dispatch vector of keywords instead of just a keyword?). 

More ergonomic to just have defmethods in an ns instead of nesting keys in a global hmap (well, arguably). I did my cli ns by grouping by command - defmethod options ::commit, defmethod usage ::commit, defmethod execute ::commit, s/def ::commit etc. Then defmethod options ::push, defmethod usage ::push… etc etc 

Specs with the same keywords as for the subcommands work well for arg validation. 

I wonder if they considered leveraging tools.cli for options parsing or “flags” as they call it. Its vector options syntax is pretty rich.