From: Rein Henrichs <reinh@...>
Date: 2010-06-14T11:50:05+09:00
Subject: Re: State of the union for Ruby CLI libraries?

On 2010-06-13 09:07:31 -0700, John Feminella said:

> I am starting construction on a somewhat complicated internal
> application whose primary interface will be the command line. In the
> past, for similar projects, I've just used OptionParser, but I think I
> need something a little beefier. Specifically, I think I need these
> features:
> 
> * colorized output
> * sensible option parsing
> * sensible enumeration of options for help output
> * support for `git`-like subcommands, e.g., `app create`, `app
> delete`, etc., that can be intuitively and cleanly mapped to methods
> * ability to be insensitive to option ordering, e.g. `app create --foo
> quux --bar` should be semantically identical to `app create --bar
> --foo quux`
> 
> Does that sort of thing exist? I've noticed there are some apparently
> more powerful alternatives like Thor, which is more of a full-stack
> scripting framework, and I'm wondering what else might be useful to
> take a look at.
> 
> Any and all suggestions would be much appreciated. Thanks!

After recently reviewing the state of the art for Ruby CLI tools myself 
as we moved Puppet to a sub-command-based executable structure, I 
couldn't find a single, cohesive library that provides all of these 
features. The domain is a full of NIH and wheel reinvention. There also 
doesn't seem to be much thought given to combining multiple tools in a 
unix-like fashion (small tools chained together to provide more 
complete functionality). They all seem to want to do a bit of 
everything but not enough of anything.

OptionParser is convenient because it's available in the standard 
library. There are a number of other option parsing tools but they 
(imo) don't provide significant benefit to offset the cost of an 
additional dependency.

As far as subcommands go, there is rake (which can be used as a 
stand-alone application DSL), thor (by Yehuda Katz), main (by Ara 
Howard), the Command code that is a part of the github gem (by Chris 
Wanstrath), the Application code that is a part of Puppet and I'm sure 
at least a dozen other reimplementations hidden in various gems and 
libraries.

I found Rake, Thor and Main gave me too much friction for the type of 
CLI tool I was interested in. Option parsing DSLs that were cumbersome, 
cryptic error handling and unweildy API design for my use case. That 
said, please try them and see if they work for you.

There are probably another dozen tools I haven't found yet or forgot 
didn't mention. Github queries for "Ruby CLI" and similar return a 
staggering number of results. I'd welcome any suggestions for my own 
use as well.

Finally I recently wrote a very small sub-command DSL gem[1] in a fit 
of my own NIH. It almost certainly doesn't do what you wantbut you are 
welcome to try it. The design goal was to do one thing (subcommands) 
and do it well, and to get out of your way and let you use your own 
tools for everything else. I would welcome feedback.

[1] http://github.com/reinh/commandant


-- 
Rein Henrichs
http://puppetlabs.com
http://reinh.com