The control email got bounced before unarchiving, here are the details of new findings.
----- Mail original ----- > unarchive 921220 > reopen 921220 > retitle 921220 xchat.desktop makes invalid use of %U, breaks at least > lxqt and flwm > affects 921220 + lxqt flwm > severity 921220 grave > thanks > I've switched away from lxqt and forgot to follow up on this issue, > but now I'm stumbling on a configure error of flwm, > which qualifies as grave under the "breaks other package" rule. > E: Sub-process /usr/bin/dpkg returned an error code (1) > Setting up flwm (1.02+git2015.10.03+7dbb30-6) ... > Exec key for 'XChat IRC' contains '%F', '%U' or '%D' at the wrong > place > dpkg: error processing package flwm (--configure): > installed flwm package post-installation script subprocess returned > error exit status 255 > Errors were encountered while processing: > flwm > Note that the freedesktop standard  says "Field codes must not be > used inside a quoted argument, the result of field code expansion > inside a > quoted argument is undefined", this could possibly be the reason for > any complaint. > If I replace the faulty line by just "Exec=xchat --existing --url %U" > the flwm configure step does succeed, which seems to confirm this > diagnostic. > Probably the better solution would be to use a wrapper script, which > could have saner behaviour (the current behaviour lauches "exec > xchat" > on any error of the first try, where it looks like what we really > want is to launch it if %U is empty. > https://specifications.freedesktop.org/desktop-entry-spec/latest/ar01s07.html > ----- Mail original ----- > > De: "Gianfranco Costamagna" <locutusofb...@debian.org> > > > À: ydir...@free.fr, 921220-d...@bugs.debian.org > > > Envoyé: Mardi 5 Février 2019 11:13:35 > > > Objet: Re: Bug#921220: xchat stops autoconnecting, complaining > > about > > "%U" and "host unknown", broken .desktop entry ? > > > Hello, > > > >OTOH when launched from cmdline the problem does not appear. > > > > > > > >And indeed the provided .desktop file shows: > > > > > > > >Exec=sh -c "xchat --existing --url %U || exec xchat" > > > > > > > >Could it be that there was a fix in a recently-dropped patch ? > > > I didn't drop any patch (you didn't even tell me which was your > > previous version, so its difficult to say) > > > but looks like a network error to me > > I guess at that time I made assumptions on not-so-recent "Drop old > and useless patch" changelog entry, my bad.