Re: Gnus search engine returns "Group nnselect:nnselect-877cqbir7v.fsf contains no messages"

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Julien Cubizolles <j.cubizolles@free.fr> writes:

> "Loris Bennett" <loris.bennett@fu-berlin.de> writes:
>
>
>> I am also experiencing the same error.  My configuration had been
>> working fine for years, but after updating Debian from 11 to 12 and
>> hence Emacs from 27.1 to 28.2 I now have this problem.  The issue
>> arises with both imap and nntp groups.
>>
>> This is what appears in *Messages* with gnus-verbose set to 10:
>>
>>   Retrieving newsgroup: nnselect:nnselect-87v8dpn1ch.fsf...
>>   Opening server fu_exchange
>>   Searching nnimap+fu_exchange:HPC...done
>>   Group nnselect:nnselect-87v8dpn1ch.fsf contains no messages
>>
> Same problem here with Emacs 30.0.50.
>
> The relevant parts of my config are:
>
> (setq gnus-search-default-engines
>       '((nnml . gnus-search-notmuch)
> 	(nntp . gnus-search-notmuch)
> 	(nnimap . gnus-search-imap)
> 	(nnfolder . gnus-search-notmuch)
> 	(nndraft . gnus-search-notmuch)
> 	(nnarchive . gnus-search-notmuch)
>         (nnselect . gnus-search-nnselect)
> 	(nnmaildir . gnus-search-notmuch)))
>
> (setq gnus-search-use-parsed-queries t)
>
> (setq gnus-secondary-select-methods
>       '((nnmaildir "Academie" (directory "~/email/Maildir-mbsync/Academie")
> 		   (gnus-search-engine gnus-search-notmuch 
>  		     		           (remove-prefix "~/email/Maildir-mbsync/Academie")))))
>
>
> On a given group from the Academie maildir, I always get the "contains
> no messages" whatever the query. notmuch returns plenty of messages
> whose filenames, as given by ‘notmuch-show-stash-filename’ are of the
> form:
>
> Stashed: /home/wilk/email/Maildir-mbsync/Academie/General/cur/1692854503.M508606P40464Q3.sadhill,U=40:2,

Hey! What would be most helpful is to see what the notmuch process
returns to Emacs, so that we can see if it's a failure to parse that
output or what.

First of all, I've recently (just a few days ago) added a little bit of
extra logging around this code. If you're using Emacs from master and
have recently updated, you can set `gnus-verbose' >= 7, and it will
message how many results the search engine returned, and how many
results Gnus was able to extract from that. Look for strings like Search
engine returned %d results. So that might at least narrow down where to
look.

In your case, it sounds like notmuch is returning results. Perhaps the
easiest thing to do would be to run notmuch on the command line the same
way that Gnus runs it. That would look like:

notmuch --config=<config_file> search --output files --duplicate=1 <query_string>

That might show you something right there. If that looks correct, maybe
you could send me a sample of the results, either on- or off-list, and I
can confirm that Gnus is able to parse them.

gnus-search-notmuch-config-file defaults to ~/.notmuch-config, I'm
actually not sure what happens if that file doesn't exist, so that's
something to consider as well.

Thanks,
Eric