[Zope-dev] Re: View component registration

[Jim Fulton]

On Jun 19, 2008, at 9:37 AM, Philipp von Weitershausen wrote:

> David Glick wrote:
>> On Jun 18, 2008, at 1:44 PM, Malthe Borch wrote:
>>> Martijn Faassen wrote:
>>>> There's one major problem that I see. What's the backwards  
>>>> compatibility story? I'm sure there are a lot of cases in lots of  
>>>> code where people look up views with a getMultiAdapter, and if we  
>>>> started registering views differently, wouldn't that code break?  
>>>> How to we get from A to B?
>>>
>>> It deserves consideration, but I don't think code will be prone to  
>>> break since we're merely providing more information to lookup a  
>>> view component, not less.
>> Exactly.  The interface passed to getMultiAdapter or  
>> queryMultiAdapter is a minimum requirement.  Making views provide  
>> IView won't stop them from providing Interface, which is the default.
>
> Well, true, view *lookup* for Interface will still work if we  
> register views for a more specific interface. But if Zope's browser  
> publication now starts looking up views with the more specific  
> interface and there are still views around that haven't been  
> registered for that but for Interface, we'll run into backward  
> compatibility problems.
>
> I suppose the browser publication would have to be smart about it  
> and do a legacy lookup for Interface if it can't find a view for the  
> specific one.
>
> Either way, it's not *that* simple...


I suggest:

- decide on and advertise the new interface

- continue to do look ups the way we do now

- update relevant zcml directives (view, page, resource. etc.) to use  
the new interface

- issue informative deprecation warnings when we register adapters  
providing Interface.

- Later, switch to looking up using the new interface.  Maybe make  
this an application option so that people can choose to use the new  
interface sooner.

Jim

--
Jim Fulton
Zope Corporation