[Zope-dev] relocating Zope 2 core interfaces - a proposal

[yuppie]

Hi again!


As discussed two days ago, I started working on integrating Five 
interfaces closer into Zope 2.8. I believe I understand the problem 
better now and like to propose a different way to resolve it:


Current State
=============

Five (now part of Zope 2.8) ships with one big interfaces.py file that 
contains z3 interfaces for Zope 2 core classes. (There are also some 
five specific interfaces in that file, but they are not subject of this 
proposal.)

interfaces.zcml states that Zope 2 implements these interfaces, but 
there are no tests to verify that and in fact many of these interfaces 
are broken in Five 1.0. (Yesterday I checked in some fixes to the Five 
trunk.) So if they are used at all in Five products, they are only used 
as marker interfaces, not to verify implementations.

I grepped through CMFonFive, SilvaDocBook and SilvaFlexibleXML: None of 
them use these interfaces.


Goals
=====

Step by step, Zope 2 should move to z3 interfaces. Where z2 interfaces 
exist, these should be improved and bridged to z3 interfaces. Missing 
interfaces should be added as z3 interfaces. Instead of maintaining 
competing interfaces, Five should support that process.

Interface locations are identifiers, so first of all I want to get these 
locations right before Zope 2.8 is released. Z3 interfaces should be 
located in an 'interfaces' module of the corresponding package. In the 
Five package they are unmaintainable.

So e.g. instead of

     Products.Five.interfaces.IObjectManager
     Products.Five.interfaces.IWriteLock

we would have

     OFS.interfaces.IObjectManager
     webdav.interfaces.IWriteLock


Proposed Solution
=================

1.) Adding ZCML that bridges existing z2 interfaces into the 
'interfaces' module of their package. [Zope 2.8.0]

2.) Copying z3 interfaces from Five.interfaces to the 'interfaces' 
module of the corresponding package. Marking those in Five as Zope 2.7 
backwards compatibility cruft. [Zope 2.8.0]

3.) Doing the same for Zope 2.7 with monkey patching code. [Five 1.0+]

4.) Making interfaces.zcml point to the new locations. [Five 1.0+]

5.) Adding unit tests that verify interfaces and implementations. [Zope 
2.8.0]


Risks
=====

I can't see a way to provide backwards compatibility for 
Products.Five.interfaces.*, but as explained above I'm hopeful this 
doesn't break many Five products.


Any comments?

Cheers,

	Yuppie