From: Pit Capitain <pit@...>
Date: 2005-05-06T17:01:59+09:00
Subject: Method hooks in singleton classes

Hello Ruby-maintainers,

currently the hooks method_added, method_removed, method_undefined are 
*not* sent to singleton_classes. Instead, the corresponding singleton 
method hooks are sent to the "attached" instance.

Example from eval.c:

   if (FL_TEST(klass, FL_SINGLETON)) {
     rb_funcall(rb_iv_get(klass, "__attached__"), singleton_added, 1, 
ID2SYM(mid));
   }
   else {
     rb_funcall(klass, added, 1, ID2SYM(mid));
   }

Is there any chance to always execute the else clause, as in:

   if (FL_TEST(klass, FL_SINGLETON)) {
     rb_funcall(rb_iv_get(klass, "__attached__"), singleton_added, 1, 
ID2SYM(mid));
   }
   rb_funcall(klass, added, 1, ID2SYM(mid));

With this change, both the singleton method hooks and the method hooks 
would be called in the case of a singleton class.

The reason I'm asking: in a library I'm writing I'd like to be able to 
catch *every* method redefinition for a given object. Something like

   o = Object.new

   def o.singleton_method_added( m )
     puts "gotcha"
   end

Currently, this works only as long as the singleton_method_added method 
isn't overridden. If someone later redefines

   def o.singleton_method_added( m )
     puts "no more"
   end

the original method isn't called anymore. Changing Ruby as proposed 
would allow me to do

   class << o
     def method_added( m )
       puts "gotcha"
     end
   end

and get notified even when singleton_method_added is redefined.

I could send patches for this change, if you like.

Regards,
Pit