[Zope-CMF] Re: GenericSetup list property purge

[yuppie]

Florent Guillaume wrote:
> On 17 Jan 2006, at 10:28, yuppie wrote:
>> The handlers for other sequences (like skin paths and object managers) 
>> just add new sequence items if the item doesn't exist already. 
>> Wouldn't that also work for list properties?
> 
> Yes but other sequences have an implicit semantics which is that 
> elements cannot appear twice. Whereas here for properties that are lists 
> we don't know the underlying semantics. It could be desired or not to 
> have an element present twice. Not in my use case admittedly, but you 
> never know.
> 
> Up to know I just added elements to the list, without removing identical 
> ones already present.
> 
> What I can do is, for now, make purge=False have the exact semantics 
> than for skins or objects (remove the old element first if it exists), 
> but we know that at some point we may have to extend that semantic to 
> provide things like append="True" or append="always" and 
> append="once"... We can probably avoid deciding that now.

Either we make sure that importing an extension profile twice doesn't 
create duplicated settings. Or we support an append="always" mode. We 
can't do both.

So I really hope we'll never have to extend the semantic in a way like that.

Cheers, Yuppie