[Telepathy] Channel-specific handles vs pending membership

[Robert McQueen]

Simon McVittie wrote:
> It's currently unclear what will happen when a channel has
> channel-specific handles (XMPP MUCs, in practice) and invitations happen.
> 
> Assume simon at srv, fred at srv and jim at srv are global handles, and
> room at conf.srv/Simon, room at conf.srv/Fred and room at conf.srv/Jim are
> the corresponding channel-specific handles in the MUC room at conf.srv.
> 
> * If Fred invites me to join room at conf.srv, will I see simon at srv or
>   room at conf.srv/Simon in the local-pending set, or is it unspecified?
> 
> * Also, will I see fred at srv or room at conf.srv/Fred in the members set, or
>   is it unspecified?
> 
> * When I accept the invitation and I get moved to the remote-pending
>   set, or if I'm trying to join a room without having been invited, which of
>   my handles will I see in the remote-pending set? (I assume it's the
>   same in both cases...)
> 
> * If I invite Jim by calling AddMembers(RequestHandles([jim at srv])), will I see
>   jim at srv or room at conf.srv/Jim in the remote-pending set, or is it unspecified?

It's unspecified, but implementation constraints should mean that they
all behave similarly. The main problem they all share is that you should
not or anyone else should not be given a room-specific handle until
they've actually joined the room, because until that's happened, you
don't know if your nick is available in the room (in the case of us
being invited), or you don't know what nick the 3rd party will take when
they join the room (in the case of inviting others).

Given this constraint, the most sane behaviour I can think of is that we
should make the pending members (local or remote) always have global
handles, and only issue the channel-specific handle when they become a
member. Its quite likely that Gabble doesn't do this
consistently/correctly, and in certain circumstances hypothesises a
channel-specific handle which either we might not be able to obtain, or
the invitee might not choose to.

We could make things a little more consistent by specifying that when
invites in rooms with channel-specific handles are accepted, the
MembersChanged signal will report only the invited global handle in
[removed], and the new channel-specific handle in [added].

Unfortunately, there's actually a situation where you can invite someone
to an anonymous room and never clear their remote pending global handle
because you never know what channel-specific handle they appear as. I
don't think there's anything we can do about that.

The alternative would be that we hypothesise a channel-specific handle
for the pending invited people (us or them) and rename them when the
invites are accepted. Without much thought, my gut feeling is that this
would be even crazier.

Thanks XMPP MUC. Thxmppmuc.

> 	Simon

Regards,
Rob