From: Austin Ziegler <halostatue@...>
Date: 2005-02-05T07:28:30+09:00
Subject: Re: [BUG] RubyGems: "No such file to load -- rubygems/builder"

On Sat, 5 Feb 2005 06:20:15 +0900, Erik Veenstra
<google@erikveen.dds.nl> wrote:
>> This is a bug, and I'm not sure the best way to handle this --
>> but the real problem is the way that Debian-family Linuxes
>> package Ruby.
> I disagree. This example is a result of the strange Ruby packages
> on Debian systems. That's true. But the same problem can occur in
> other situations as well. The way the require method of RubyGems
> catches the LoadError exception is the real problem.

It's not the only one. Any time *anything* catches a LoadError, the
real exception can be hidden, which is why I said I'm not sure the
best way to handle this. I faced something similar to this in Ruwiki
(because I have a fairly sophisticated require technique to try to
discover things in various places since Ruwiki can be installed in
multiple fashions), and I'm not sure I'm happy with the result that
I managed there, either.

In part, one might argue that silently catching a LoadError is a bad
thing. In some testing code that I have for Text::Format, I do:

  begin
    require 'text/hyphen'
    hy = Text::Hyphen.new
  rescue LoadError
    begin
      require 'tex/hyphen'
      hy = TeX::Hyphen.new
    rescue LoadError
      print 'S'
      return true
    end
  end

This way, I can exercise the external interfacing of Text::Format
with one of the two available hyphenation libraries -- but I lie to
test/unit in order to do so, sort of. However, if the require of
text/hyphen failed for a reason *other* than text/hyphen not being
installed (e.g., text/hyphen required a library that it currently
doesn't but is broken because of Debian packaging decisions, for
example), this test program would hide that.

As I said, I'm not sure *how* it should deal with this. Perhaps a
variant of LoadError that chains the pieces together, e.g.,

  class GemLoadError < LoadError; end

and set it up to keep track of any other LoadError or GemLoadError
caught?

-austin
-- 
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca