[Zope-CMF] Proposal: Action expression contexts

[Miles]

Hi,

One of the things that we find slightly cumbersome here in our 
applications is that when defining actions, there's no easy way to 
adjust the variables available to an expression.  This tends to make the 
expressions longer and harder to read, plus commonly used variables are 
calculated multiple times.

For example, my application has a concept of a "page", and I would like 
to make this available as a variable rather than work it out each time.

Therefore I think it would be useful to adjust getExprContext in 
CMFCore.Expression so that it is pluggable, by using a factory to create 
the ExpressionContext.  In that way I can register different ones as 
required.

Is this a desirable change?

Miles