[Zope-CMF] CMF 1.6

[Alec Mitchell]

On Wednesday 16 November 2005 01:41 pm, Florent Guillaume wrote:
> I'd like to have some clarifications from the Plone team about what
> they expect to do w.r.t. events in CMF 1.6.
>
> I see two possibilities:
> 1. you guys are prepared to do the work needed for Plone products to
> use super() in manage_afterAdd & co, in which case I can merge my
> branch into CMF 1.6
> 2. you feel that's too dangerous and, as Plone intends to use CMF
> 1.6, I'll merge for CMF 2.0 only.
>
> Be aware that if 2. is chosen, you won't be able to use Zope 3 events
> at all with CMF 1.6.

I'm a bit worried about the potential consequences here, so I'd say #2 is 
probably a necessity.  Even then, using super in a such a ubiquitously 
inherited class seems very dangerous.  Though I'm by no means an expert on 
the pitfalls of super(), my worry is that there are many products out there 
that subclass CMFCatalogAware, either directly or through 
BaseObject->CatalogMultiplex->CMFCatalogAware.  Even if we move to using 
super in BaseObject and CatalogMultiplex, we still have the problem of 
subclasses of BaseObject (i.e. nearly everything in the plone universe these 
days) needing to use super in any manage_after/before* methods (overriding 
e.g. manage_beforeDelete and delegating back to the parent class is quite 
common).

Am I misunderstanding here, or is this change going to break any 3rd party 
product that uses CMFCatalogAware and overrides manage_before* without using 
super()?  The fix for these products would be for them to also use super and 
possibly reorder their baseclasses so that the super users come first 
(though according to http://fuhm.org/super-harmful/, that still may result 
in unexpected behavior).  This would seem unacceptable for the next point 
release of Plone.  If this is going into CMF 2.0, then it's yet another 
reason for plone to stay clear of CMF 2.0 for a little while.

The big problem with this move is there's no way to give product developers 
warning.  They can't start using super now, because none of the base classes 
use it, but once super is in place in the base classes developers will need 
to start using it immediately or risk strange breakages.  Maintaining 
product compatibility between versions of CMF/Plone will become nearly 
impossible.  Doesn't look like there are any alternatives for getting 
add/delete/copy events working under zope2 though.

Alec