[Jmap] Draft messages - mutability

[Bron Gondwana <[e-mail]>]

I'm starting this thread to discuss the mutability of fields in isDraft: true messages.

In Cyrus IMAPd right now, we create the "MSGID" field as the sha1 of the "RFC822" raw message content as would be delivered over IMAP.  That's lovely for non-draft messages (except that we'll probably switch to using blake2 for new messages soon).

But it sucks for drafts, because it means that every time you edit a draft, you get a new MSGID.  Futhermore, you can't edit a draft via JMAP with ['setMessages', {update:{}}] because the fields that you want to edit are immutable, so instead you are doing ['setMessages', {create:{all the fields}, destroy: ["the old id"]}] which is a horrible way to edit drafts.

A somewhat similar discussion is happening over in CalConnect around the idea of saving draft ICALENDAR items on a server without sending out scheduling messages about them until they have finished being edited.

So the question for JMAP becomes: is a "draft message" the same datatype as a "message", or do you handle them completely differently?  Clearly you want to show them in-thread with the message they are in reply to in an interface, but how does that look over the protocol?

Bron.

-- 
  Bron Gondwana
  [e-mail]