Major QDBus regression in Qt6 with potential impact on KDE

[Bartosz Golaszewski]

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.

> And then i realized my distro doesn't seem to provide pydbus_manager so yep
> too hard to even try to reproduce for something that personally is not at all
> pressing for me yet.
>

Yeah the requirements.txt in the repo points to the relevant github repo.

Bart