[Fetchmail-devel] IMAP and UIDs

[Peter G. <pg...@gm...>]

Hi,

I'm thinking of taking a stab at the "Let IMAP code use UID and
UIDVALIDITY rather than relying on flags that everyone can alter" bug
since relying on the \Seen state is hurting my multi-client workflow.

I have a few questions before I get started

1. Do we need to tackle UIDVALIDITY storage and validation as part of
this? Since client-side handling UIDVALIDITY changes is had to do
correctly, most (all?) IMAP servers don't do this unless they
absolutely have to (e.g. there has been some sort of corruption in
their underlying storage layer). If we can punt on UIDVALIDITY, we can
store IMAP UIDs similarly to how we handle POP UIDs. Any advice here?

2. POP UIDs are alphanumeric strings. IMAP UIDs are unsigned 32-bit
integers. In order to re-use as much of the existing idlist code as
possible, I was thinking of storing UIDs as strings, e.g. via
sprintf(id, "%lu", uid). Not my favorite solution but it should be
less invasive than other ideas (e.g. making 'idlist.id' a union).

3. For the configuration impact of this, allowing --uidl to affect
IMAP sessions would be the natural choice except that it may have
unexpected consequences for users who were relying on that being a
no-op. In this case the consequence would be that they would have an
idfile get populated. I think this is probably okay as long as we
preserve the existing behavior that marks fetched messages as seen. I
think we should add a new --leave-unseen flag that allows uses to
opt-in to marking messages as un-seen after fetching.

Thanks,
Peter