Re: interested in writing a commandline option parser for ruby?

On Wed, May 12, 2010 at 11:44 AM, William Morgan
<[e-mail]> wrote:
> Reformatted excerpts from Michael Fellinger's message of 2010-05-11:
>> I have no idea what caused this rage of you,
>
> Suboptimal software.
>
>> but would you kindly tell me what's wrong with OptionParser
>> (optparse.rb in stdlib)?
>
> 1. Too many positional arguments. Which is the correct version?
>
> =C2=A0opts.on( '-f', '--float NUM', Float, "Convert to float" )
> =C2=A0opts.on( '-f', '--float NUM', "Convert to float", Float )
>
> If you have to look it up, optparse fails.

The first one on first glance, but I'm using that library for years now.

>
> 2. The use of blocks. 99% of the time you're just throwing stuff in a
> hash anyways, in which case you now have to maintain the mapping between
> hash keys and arguments. The rest of the time you're doing complicated
> stuff in the blocks, in which case you have code mixed in the middle of
> your argument list.

The first one is true, it used to be nicer in 1.8 when people abused
the block pipes ;)
You can put longer code into methods and use them as blocks:
o.on('-h', '--help', 'read me', &method(:help))
See http://github.com/manveru/ver/blob/master/bin/ver#L167 as an example.

> 3. No notion of default arguments. You have to explicitly write them
> into your code, e.g. by using a hash and initializing it.

You have to put your defaults somewhere, might as well be a Hash.

> 4. If optparse knows your argument is named '--float', why doesn't it
> automatically generate a short option '-f'? (Likewise, if optparse knew
> what your default value was, it could infer the type-checking for you.)

Because you'd rather not provide a short version for some stuff,
especially if there are two options called --float-min and
--float-max?
Again, a default value doesn't need to have anything to do with the
accepted values.

> 5. Complicated API. on_head, on_tail, make_switch, etc.

The API is actually very powerful, it takes a little effort to learn,
but you can go very far with it.
For example, I've implemented the ramaze binary using optparse so i
can actually handle subcommands without code duplication:
http://github.com/manveru/ramaze/blob/modular-bin/lib/ramaze/bin.rb
http://github.com/manveru/ramaze/blob/modular-bin/lib/ramaze/bin/start.rb
http://github.com/manveru/ramaze/blob/modular-bin/lib/ramaze/bin/stop.rb

> 6. I like for my help pages to be wrapped nicely, e.g.
>
> =C2=A0Options:
> =C2=A0 =C2=A0 --delete, -d: =C2=A0 Delete everything
> =C2=A0 =C2=A0--restore, -r: =C2=A0 Restore everything. Of course this doe=
sn't actually
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 wor=
k. What's gone is gone. But it might make the user
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 fee=
l hopeful for a second, and, after all, isn't that
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 val=
uable in and of itself? (default: true)
> =C2=A0 =C2=A0 =C2=A0 --help, -h: =C2=A0 Show this message
>
> Optparse just makes a big blob.

Formatting can be controlled when initializing:
http://github.com/ruby/ruby/blob/trunk/lib/optparse.rb#L784-791
And it can be even more controlled when you do the actual output:
http://github.com/ruby/ruby/blob/trunk/lib/optparse.rb#L359-371

Not that I ever cared about that, I don't even understand what you
mean with big blob,
just pointing out it might be possible to get your preferred formatting too=
 :)

> That's all I can think of now...

Thanks.

--=20
Michael Fellinger
CTO, The Rubyists, LLC