[Jmap] Re: Mahesh Jethanandani's Discuss on draft-ietf-jmap-contacts-09: (with DISCUSS and COMMENT)

[Neil Jenkins <[e-mail]>]

On Mon, 3 Jun 2024, at 08:31, Mahesh Jethanandani wrote:
> Thanks for that explanation. How about this?
> 
> OLD:
> If false, any attempt to destroy an AddressBook that still has ContactCard in it will be rejected with an addressBookHasContentsSetError. If true, any ContactCards that were in the AddressBook will be removed from it, and if in no other AddressBooks they will be destroyed.
> 
> NEW:
> If false, any attempt to destroy an AddressBook that still has ContactCard in it will be rejected with an addressBookHasContentsSetError. If true, any ContactCard that is in the AddressBook that is set to be destroyed. will be removed from it, and if the ContactCard does not exist in any other AddressBooks it will be destroyed.

Thanks. I've tweaked it slightly but kept the substance of your rephrasing:

If false, any attempt to destroy an AddressBook that still has a ContactCard in it will be rejected with an `addressBookHasContents` SetError. If true, any ContactCard that is in the AddressBook will be removed from it, and if such a ContactCard does not belong to any other AddressBook it will be destroyed.

> My question is about a ContactCard that is present in multiple AddressBooks. Take your example above, Bill appears in two AddressBooks, Work and Personal. And I will take the example of Apple’s Contacts App that I use. I use the search capability in the App to find the ContactCard for Bill, find it, select it, and hit the delete button. What happens?

Well, the exact answer is that Apple's Contacts app currently only supports CardDAV, which does not support a contact card belonging to more than one address book. So this will destroy the card.

A server that supports both CardDAV and JMAP Contacts can choose either:
 • To limit contacts to also only being in one address book (via the maxAddressBooksPerCard capability <https://www.ietf.org/archive/id/draft-ietf-jmap-contacts-09.html#name-addition-to-the-capabilitie>).
 • To support an implementation-specific mapping. I would expect at Fastmail for example we would implement this as just removing it from the single address book, not destroying the card and thus removing it from both.
Similarly, if Apple's Contacts client added support for JMAP Contacts, it could make a UI decision of what to do in this instance, but that is independent of the API exposed.

> Based on all the explanations, what I understand is:
> remove: A ContactCard can be removed from an AddressBook, but MAY NOT be destroyed.
> destroy: Once a ContactCard is removed from the last AddressBook that it is existed it, it is destroyed

This doesn't make sense to me, perhaps because I'm coming from a JMAP core understanding first. JMAP is at it's heart a CRUD mapping. So if I have a ContactCard I can either update it (modify a property on the object) or destroy it. The AddressBook(s) that a ContactCard is in are modelled as a property on the ContactCard containing a set of AddressBook ids. A ContactCard MUST belong to at least one AddressBook.

Therefore, you can either:
 • Update the contact card to add or remove AddressBook ids, i.e. to add or remove it from an address book. But you can't violate the constraint that it MUST belong to at least one address book via an update.
 • Destroy the contact card.
Does that clarify?

Cheers,
Neil.