[Zope-dev] ZPT: defer expression fix

[Christian Heimes]

PageTemplates have an undocumented features called defer:. It's a kind 
of lazy initialization of variables.

I've fixed to issues in my tiran-zpt-pydefer branch (svn):

  * DeferWrappers weren't working inside a python expression because 
PythonExpr didn't know about them

  * DeferWrapper didn't cache the result of the expression like ordinary 
vars do.

I would like to merge my branch into 2.7 and 2.8 if I get an ok.

Christian