bug#41530: 28.0.50; gnus-cloud-download-all-data does not mark articles as read

[Kévin Le Gouguec]

Hello,

I'm having trouble setting up gnus-cloud.  Here are the steps I
follow:

0. Clean the slate.
    - On my IMAP server's webmail:
        - delete all mails generated by gnus-cloud,
        - delete the Emacs-Cloud folder.
    - In system 1's .newsrc.eld:
        - remove all gnus-cloud-* variables,
        - remove Emacs-Cloud from gnus-newsrc-alist.
    - On system 2: remove .newsrc.eld.

On both systems 1 and 2, gnus-cloud-method is customized to
"nnimap:gmail".

1. On system 1: upload a CloudSynchronizationDataPack™.
    - Start Emacs & Gnus.
    - In the *Server* buffer:
        - hit i on NNTP servers.
    - In the *Group* buffer:
        - hit ~ u, enter & confirm passphrase.

So far, things seem to be working… maybe?  I have a new mail from
nobody@gnus.cloud.invalid in the Emacs-Cloud group, entitled

> (sequence: UNKNOWN type: :full storage-method: epg)

(Looking at gnus-cloud.el, i have no idea how this "UNKNOWN" ends up
here, since I see no reason for gnus-cloud-sequence to be nil.)

If I decrypt this mail, I can see one Lisp form per subscribed group,
of the form

> (:type :newsrc-data :name "…" :contents (…) :timestamp "…")

Moving on…

2. On system 2: try to download the CloudSynchronizationDataPack™.
    - Start Emacs & Gnus.
    - In the *Server* buffer:
        - hit i on NNTP servers,
        - subscribe to groups system 1 is subscribed to.
    - In the *Group* buffer:
        - hit ~ d.

At this point I'd expect

1. to be prompted for the passphrase entered in step 1,
2. NNTP articles I've read on system 1 to be marked read on system 2.

Instead, nothing happens: no passphrase prompt, and all articles in the
NNTP groups I subscribed to remain unread.  I just get this in
*Messages*:

> nnimap read 0k from [IMAP server].

I tried to dig into this; all I could figure out is that
gnus-cloud-available-chunks returns nil.

I *think* this is not linked to bug#40280; I applied the patch and not
much changed.  From what I understand, the patch fixes a problem that
happens later, when processing whatever gnus-cloud-available-chunks is
supposed to return.

I don't know if this might be linked to bug#28845.


Let me know if there is anything I can do to help debug this.


Thank you for your time.


In GNU Emacs 28.0.50 (build 11, x86_64-pc-linux-gnu, GTK+ Version 3.22.30, 
cairo version 1.15.10)
 of 2020-05-25 built on klegouguec-HP-ProBook-450-G1
Repository revision: 0cdedf612b9da14fccc39c4a4e81cbf400e4552f
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12005000
System Description: Ubuntu 18.04.4 LTS

Configured using:
 'configure --with-xwidgets --with-cairo'

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS JSON
PDUMPER LCMS2 GMP

Important settings:
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix