bug#70054: 30.0.50; Unknown ids in References: break threading

[Eli Zaretskii]

> Cc: Eric Abrahamsen <eric@ericabrahamsen.net>, Jose A Ortega Ruiz 
> <jao@gnu.org>
> From: Andrew Cohen <acohen@ust.hk>
> Date: Thu, 09 May 2024 15:55:11 +0800
> 
> >>>>> "EZ" == Eli Zaretskii <eliz@gnu.org> writes:
> 
> [...]
> 
>     EZ> Ping!  Can we make some further progress with this bug report?
> 
> I worked with Jose to track everything down. This isn't a gnus bug and
> the bug report can be closed.

Thanks, done with this message.

> Slightly more detail: the protonmail bridge adds non-existent ids to the
> references header of messages (presumably used in some internal way by
> the protonmail bridge). 'gnus is resilient in handling these: if
> collecting threads by subject (the default) everything "just works". And
> in case you (optionally) want to only use the references header for
> threading, gnus has a way to alter the headers for exactly this
> occasion: 'gnus-alter-header-function.  So the following:
> 
> (setq gnus-alter-header-function 'fix-protonmail-references)
> 
> (defun fix-protonmail-references (header)
>   (setf (mail-header-references header)
>         (mapconcat
>          #'(lambda (x) (if (string-search "protonmail.internalid" x) "" x))
>          (gnus-split-references (mail-header-references header)) " "))
>   header)
> 
> will work.
> 
> I think this deserves to be in the gnus manual.  I have a commit in my local
> tree to do this, which I will push to master.

Thanks again.