qtchooser should have a fallback mechanism (for version AND architecture)

[Julien Aubin]

HI,

Steps to reproduce :
DO : perform an upgrade of Kubuntu with latest updates of qdbus.
DO : remark that package qdbus-qt5 is normally not installed.
DO : logout of KDE
DO : login into KDE
EXPECT : login runs fine
ACTUAL : cannot login within KDE, with message "qdbus cannot be started"

Now install qdbus-qt5 and everything is working fine. Note that if that package is missing when trying to run qdbus from the command line it complains it is missing a qt5 qdbus.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: qdbus 4:4.8.5+git192-g085f851+dfsg-2ubuntu4
ProcVersionSignature: Ubuntu 3.13.0-18.38-generic 3.13.6
Uname: Linux 3.13.0-18-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.13.3-0ubuntu1
Architecture: amd64
CurrentDesktop: KDE
Date: Fri Mar 21 21:14:11 2014
ProcEnviron:
 LANGUAGE=fr_FR
 TERM=xterm
 PATH=(custom, no user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: qt4-x11
UpgradeStatus: Upgraded to trusty on 2014-03-20 (0 days ago)

[Matt Smith (melkor-orangepalantir)]

I had the same thing happen after I updated. I got into kde by linking /usr/bin/qdbus:

/usr/bin/qdbus -> /usr/lib/x86_64-linux-gnu/qt4/bin/qdbus

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dmitry Shachnev (mitya57)]

In fact, qtchooser should provide some kind of fallback when Qt4 version of some tool is installed and a Qt5 version is not.

[Rohan Garg (rohangarg)]

The package should most certainly not depend on qt5-default, because we still ship KDE SC built with Qt4.

I introduced a change in kde-workspace so that kde-workspace now uses qtchooser at run time to run qdbus in startkde. What needs fixing is that kde-workspace should depend on qtchooser.

[Rohan Garg (rohangarg)]

Argh wrong report, sorry about the noise :(

[Harald Sitter (apachelogger)]

Another fun version of this is bug #1312895

Since both qdbus:i386 and qdbus:amd64 would satisfy a qdbus dependency one can end up with the foreign architecture package (e.g. i386) which consequently fails to start because the config will want to look in the amd64 path rather than the i386 one.

also do note
https://launchpadlibrarian.net/175232479/03_QT_SELECT-notWorking.txt
for output of qdbus invocation

and
https://launchpadlibrarian.net/175232444/02_dpkg_qdbus.txt
for dpkg saying that there is only one qdbus and that's for the foreign arch

[Dmitry Shachnev (mitya57)]

FWIW I started work on this at https://codereview.qt-project.org/82702, but we didn't reach a consensus about how the blacklist/whitelist should look like.

[Launchpad Janitor (janitor)]

This bug was fixed in the package qtchooser - 39-g4717841-3ubuntu1

---------------
qtchooser (39-g4717841-3ubuntu1) utopic; urgency=medium

  * Add a proposed patch from upstream:
    - Implement-fallback-mechanism.patch (LP: #1295835)
 -- Timo Jyrinki <email address hidden> Mon, 06 Oct 2014 16:39:42 +0300