Major QDBus regression in Qt6 with potential impact on KDE

[Albert Astals Cid]

El divendres, 16 de desembre de 2022, a les 16:20:29 (CET), Bartosz 
Golaszewski va escriure:
> On Fri, Dec 16, 2022 at 4:05 PM Albert Astals Cid <aacid at kde.org> wrote:
> > El divendres, 16 de desembre de 2022, a les 15:45:17 (CET), Bartosz
> > 
> > Golaszewski va escriure:
> > > On Fri, Dec 16, 2022 at 3:27 PM Albert Astals Cid <aacid at kde.org> wrote:
> > > > El dijous, 15 de desembre de 2022, a les 19:55:59 (CET), Bartosz
> > > > Golaszewski>
> > > > 
> > > > va escriure:
> > > > > Hi!
> > > > > 
> > > > > I'm working on a piece of software that extensively uses QDBus. The
> > > > > project is based on Qt5. I'm trying to upgrade it to Qt6 but have
> > > > > encountered an issue with QDBus that's described in detail in my
> > > > > official bug report[1]. The report includes a link to a github repo
> > > > > with reproducible examples.
> > > > > 
> > > > > Short version is: it's impossible to connect to the InterfacesAdded
> > > > > or
> > > > > InterfacesRemoved signals (and potentially to any signals that have
> > > > > slightly more complex arguments) on the system bus with QDBus in Qt6
> > > > > (unless one enables QDBUS_DEBUG=1 in which case it's possible). I
> > > > > suspect some timing issue/race condition but don't know Qt enough to
> > > > > debug it.
> > > > > 
> > > > > While my project is not related to KDE, I thought I'd bring it to
> > > > > your
> > > > > attention (as KDE is scheduled to upgrade to Qt6). This bug
> > > > > definitely
> > > > > affects KDE as for instance the networkmanager-qt project subscribes
> > > > > for the InterfacesAdded signal of NetworkManager's paths and will no
> > > > > longer work with Qt6.
> > > > > 
> > > > > Has anyone in the KDE community encountered this bug yet? How does
> > > > > KDE
> > > > > deal with blockers like this? Seems like Qt is not eager to fix it
> > > > > on
> > > > > their side.
> > > > 
> > > > Remember Qt is Free Software, if you are blocked by it, you seem like
> > > > a
> > > > good person to try to fix it :)
> > > 
> > > Oh I tried and failed. :(
> > > 
> > > So instead I thought I'd find a) paying clients, b) projects with some
> > > serious stake in QDBus that could help and report it to them in hope
> > > of finding help. :)
> > 
> > Fair enough :)
> > 
> > As a suggestion next time attach the code, don't put it in comments (and
> > provide a full buildable example, yours doesn't have a buildsystem), makes
> > me super sad that i have to copy and paste and i was almost super close
> > to not even bothering trying it.
> 
> What are you talking about, there's a link to my github repo at the
> bottom and it includes requirements.txt for python and a .pro file for
> Qt.

For those that are not put off by his somewhat agressive manners and still want 
to invest their spare time to help him, the link to github repo is hidden in 
the "here" word of the "The examples I posted are available here." in a 250 
lines comment.

Cheers,
  Albert