From: Gavin Sinclair <gsinclair@...>
Date: 2004-08-24T13:57:19+09:00
Subject: Re: optparse [feature request: subcommand support]

On Tuesday, August 24, 2004, 7:24:19 AM, Jim wrote:


> Brett Williams said:
> [...]
>> The feature is the ability to do what I call CVS-style subcommands, i.e.:
> [...]
>> Does this sound reasonable? Is there anyone else who'd like this kind of
>> thing? Or am I on my own?

> RubyGems uses CVS style commands, so it would have been useful there.

> One question: Is it worth loading up optparse with this functionality, or
> does it make sense to put it in a different object?

Different class, IMO.  I think the RubyGems implementation is quite
good, with the Command class.  Each command (admin, checkout, ...) is
a subclass of Command and specifies its own optparse options.  In
this way optparse and Command work together nicely.

In CVS there are some options shared across commands, so you can do
this, for instance:

  module LocalRecursiveOptions
    def add_local_recursive_options
      add_option('-L', 'Local command only, no recursion') do
        options[:domain] = :local
      end
      add_option('-r', 'Run command on all subdirectories recursively') do
        options[:domain] = :recursive
      end
    end
  end

  ...

  class UpdateCommand < Command
    include LocalRecursiveOptions
    def initialize
      add_option('-P', 'Prune empty directories') do ... end
      ...
      add_local_recursive_options                # <--------------
    end
  end

  class LogCommand < Command
    include LocalRecursiveOptions
    def initialize
      add_option('-h', 'Only print header') do ... end
      ...
      add_local_recursive_options                # <--------------
    end
  end

I plan to put this command framework into its own library and include
it in addlib -- sometime in the next 12 months.  If others are
interested in this approach or any other, please go ahead.

Cheers,
Gavin