From: furtive.clown@...
Date: 2008-02-29T02:49:59+09:00
Subject: Re: Proposed Solutions - Was [ Re: Monkeypatching is Destroying Ruby 	]


Topmost-level code could set up callbacks before the 'require' lines
for the needed libs.  It would be the client's responsibility to check
for changes and adapt to them.

SingletonListener.new(Array) { |singleton|
   singleton # => Array

   {
      :reopened_begin => lambda {
         # Encountered 'class Array' line ... probably only useful for
thread sync
         # ...
      },
      :reopened_end => lambda {
         # Encountered corresponding 'end' for the above 'class Array'
         # ...
      },
      :method_added_begin => lambda { |method_name|
         # Someone has begun adding a method, either with the line
         # 'def foo' or define_method or otherwise
         method_name # => String
         # ...
      },
      :method_added => lambda { |method|
         # Forwarded from Module's method_added
         method.class # => UnboundMethod
      },
      :method_removed => lambda { |method|
         # Forwarded from Module's method_removed
         # ...
      },
      :const_added => lambda { |const_name, value|
         # ...
      },
      :const_removed => lambda { |const_name, value|
         # ...
      },

      # ... other callbacks ...
   }
}

For example I plan to define Array#foo, but I get a callback from the
library when it defines foo.  After I've 'require'd everything I need,
but before I've required my libs, I could run a unit test on the
existing foo.  If the results are identical to the test results of my
implementation, I'd perhaps leave it alone.  If not, then at least I
know.

This could all be done without SingletonListener, but the idea is to
have a common idiom which people recognize and expect (if not
SingletonListener then something else).

--FC