From: Caleb Clausen <vikkous@...>
Date: 2010-03-04T07:50:23+09:00
Subject: Re: Class vs Module in constant lookup

On 3/3/10, Peter McLain <peter.mclain@gemstone.com> wrote:
>    Well, the code isn't mine, but I'd still like to understand if
> there is a rationale for the difference in behavior, or if this is
> just another MRI implementation detail that's leaked out.  Currently,
> MagLev returns "constant" for both classes and modules, but that
> breaks third party code.  E.g,:
>
>      return unless defined? RDoc::VERSION # RDoc 1 does not have VERSION
>      # code that blows up if RDoc 1 being used...
>
> One could argue that the proper test, which works for both classes and
> modules in all ruby implementations, is:
>
>      return unless RDoc.const_defined? :VERSION
>
> But I'd still like to understand if the difference in behavior is
> intended or an implementation quirk, and if it is intended, what the
> rationale is.

Ok, I see your problem, and I sympathize.

Collisions of the toplevel constant VERSION with VERSIONs defined
inside classes are a repeated snafu. (It's bitten me.) This is
probably why MRI 1.9 no longer defines VERSION, but RUBY_VERSION
instead.

I'd suspect this is unintended, but for an authoritative answer you'll
have to get matz or another core maintainer to chime in. You might ask
on ruby-core; I suspect those guys don't pay a lot of attention to
this list nowadays.