From: Trans <transfire@...>
Date: 2005-08-12T18:41:11+09:00
Subject: Re: Dear RubyGems: Perhaps a better way to override require...


Ryan Leavengood wrote:

> This does seem better, but only if everytime someone overrides require in
> an included module they be sure to call super.
>
> Also it seems to be the alias method is fine, as long as everyone uses a
> unique name for the old method:
>
> module Kernel
>   alias :_old_require_ :require
>   def require(s)
>     puts 'New require, now calling _old_require_...'
>     _old_require_(s)
>   end
> end
>
> module Kernel
>   alias :_some_old_require_ :require
>   def require(s)
>     puts 'New require, now calling _some_old_require_...'
>     _some_old_require_(s)
>   end
> end
>
> require 'English'
> puts $PID
> __END__
>
> C:\_Ryan\ruby>ruby require_test.rb
> New require, now calling _some_old_require_...
> New require, now calling _old_require_...
> 3408
>
> If unique names aren't used, the result is an infinite loop.

That's what I expected too. But when I tried, it didn't work so well.
My aliased version was working fine until I installed RubyGems.
Appaerently it was running my version twice. Thus escaping twice, "[]"
-> "%5B%5D" -> "%255B%255D". Perhaps this is b/c RubyGems uses a rescue
clause and retries and so ends up passing the name to my routine again.
Not sure.

But you also make a good point about my inheritance chain version.
Someone else using the alias technique after mine would by pass mine
altogether. It works with RubyGems only b/c RubyGems loads first.

In thinking it over some, I suspect the best solution is either to
change the built-in require to support an observer-type pattern, so one
can tap into it. Or we simply need to agree on a standard, which I
imagine would be basically:

  module Kernel
    # Always available bypass.
    # This should be built into ruby.
    alias __require__ require
  end

  module ARequireOverider
    def require( path )
      # ...
      begin
        super( newpath )  #  <----.
      rescue LoadError    #    or vise-versa
        super( path )     #  <----'
      end
    end
  end

  class Object
    inculde ARequireOverider
  end

T.