Hi--

I recently cam across an interesting conflict between open-uri.rb and
Facets rendition of kernel/metaid.rb. Facets defines a general
extension Kernel#meta, and open-uri defines OpenURI::Meta#meta. open-
uri uses OpenURI::Meta to extend StringIO via singleton. This is all
fine, but then open-uri checks to see if a StringIO object has been
extended by doing:

  io.respond_to? :meta

And that's where the problem lies, b/c if you've loaded 'facets/kernel/
metaid' you're going to get a false positive here. Now the best remedy
is open-uri to be more precise:

  io.is_a? OpenURI::Meta

That fixes the the problem. But it raises an interesting question.
I've used #respond_to? myself from time to time thinking it was oh, so
duck-type kosher; never realizing that it might clash with general
extensions.

So where lies the fault in this conflict? Are extensions the bad guy,
or is respond_to? really not a good oop concept? Or..?

T.