bug#36714: 27.0.50; Gnus nnmaildir taking long time to recursively visit sub-Maildirs

[Jean Louis]

* Eric Abrahamsen <eric@ericabrahamsen.net> [2019-07-18 21:01]:
> I think you're right, and in a sense it is definitely a bug, but a lot
> of people have run into this and I've seen some saying there's not much
> to be done. So that didn't sound very encouraging.
> 
> Could you do M-x toggle-debug-on-quit, start up Gnus, let it hang for a
> bit, then do C-g and post the resulting backtrace here? It's fairly
> obvious what's going on, but it would be good to
> see the specifics.

Debugger entered--Lisp error: (quit)
  
file-name-as-directory("/home/data1/protected/Maildir/info@codepink.org/.n...")
  nnmaildir--scan("info@codepink.org" nil #<hash-table equal 1913/47714 
0xd41cb5> nil "/home/data1/protected/Maildir/" directory-files)
  nnmaildir-request-scan(find-new-groups "")
  nnmaildir-request-list("")
  nnmaildir-request-newgroups("Thu, 18 Jul 2019 18:11:09 +0200" "")
  gnus-request-newgroups("Thu, 18 Jul 2019 18:11:09 +0200" (nnmaildir "" 
(directory "~/Maildir")))
  gnus-ask-server-for-new-groups()
  gnus-find-new-newsgroups()
  gnus-setup-news(nil nil nil)
  #f(compiled-function () #<bytecode 0x995efd>)()
  gnus-1(nil nil nil)
  gnus(nil)
  funcall-interactively(gnus nil)
  call-interactively(gnus record nil)
  command-execute(gnus record)
  execute-extended-command(nil "gnus" "gnus")
  funcall-interactively(execute-extended-command nil "gnus" "gnus")
  call-interactively(execute-extended-command nil nil)
  command-execute(execute-extended-command)

> The nnmaildir servers keep track of their directory modtime, which is
> both set and read only once, in `nnmaildir-request-scan'. So at least it
> should be fairly easy to see what's happening there. Gnus doesn't save
> the modtimes, though -- perhaps a potential solution could involve
> saving the maildir modtimes in newsrc.eld.

Can that scan be turned off as option?

I do not even need to list the folders. I just
want to read the main ~/Maildir folder but not
sub-Maildirs within Gnus.

And then when at some point of time, when I need
to access the Maildir folder I should be able to
have function to give it folder directory and that
folder is being read, and that I can view messages
and reply to them.

Any clues? I would like to have that feature from
plain Emacs without extra packages, just to list,
read Maildirs, refile Maildirs, and be able to
reply.

Does that functionality exists within Gnus or
nnmaildir, even if not plainly visible?

> > And my other question is, is there a way to quickly access
> > Maildir/email2@example.com by using Gnus? Some function maybe to just
> > write the email address or fetch it from database, and to open the
> > Maildir with nnmaildir?
> 
> I'm not entirely sure what you mean here, but one suggestion I have is
> to create four different nnmaildir select methods, one for each of your
> email addresses. I think that's how Gnus is expecting this sort of thing
> to be set up, and it might make it easier for you to access, as well.

Would that be possible on the fly?

For example I have email address on screen, find
it at point and quickly switch to Maildir by email
address?

Jean