Re: [Docutils-develop] Re: Directives branch

[David G. <go...@py...>]

[David Goodger]
> If we want to use inheritance for the option specs, let's use
> inheritance.  We could set up a set of classes for individual option
> specs, and include them in directive classes.  I worked up a proof of
> concept, attached.  Run it as a script to see the result.

I have reworked the proof of concept to make options simpler and
easier; attached.  Instead of using super() calls, it uses the option
spec class's __mro__ method to manually determine the superclasses and
calls their setup() methods in reverse MRO order.  This definitely
makes option spec inheritance easier to implement by factoring out the
bookkeeping.

I also removed the BunchDict/StructDict technique, which although
cool, is deep black magic and unnecessary.

I tried the autosuper metaclass mechanism described in the
descrintro_, but it didn't help enough to be useful.  It reduced
``super(OptionB, self).__init__()`` calls to
``self.__super.__init__()``, but these calls were still needed, and
they still had to be after the assignments to work.  Class-private
names were necessary for this to work, which means that we'd have had
to ensure that all OptionSpec subclasses had unique names.  Not worth
it.

.. _descrintro:
   http://www.python.org/download/releases/2.2.3/descrintro/#metaclasses

-- 
David Goodger <http://python.net/~goodger>