Bug#898050: libitalccore is marked Multi-Arch: same but is not coinstallable

[Francois Gouget]

Package: libitalccore
Version: 1:3.0.3+dfsg1-3
Severity: normal

Dear Maintainer,

Trying to install the amd64 and i386 versions of this package results in the 
following error:

# apt-get install libitalccore:amd64 libitalccore:i386
[...]
Setting up libqt5svg5:i386 (5.10.1-2) ...
dpkg: dependency problems prevent configuration of libitalccore:i386:
 libitalccore:amd64 (1:3.0.3+dfsg1-3) breaks libitalc and is installed.
  libitalccore:i386 (1:3.0.3+dfsg1-3) provides libitalc.

dpkg: error processing package libitalccore:i386 (--configure):
 dependency problems - leaving unconfigured
Processing triggers for libc-bin (2.27-3) ...
Errors were encountered while processing:
 libitalccore:i386


So the source of the issue seems to be that libitalccore:
* Provides the libitalc virtual package
* Breaks + Replaces the libitalc virtual package

Apt seems to consider that this means libitalccore:amd64 breaks libitalccore:i386 
through the libitalc virtual package which prevents them from being coinstalled.


One strange thing is that, if I understand 7.6.1 of the Debian Policy Manual 
correctly, Breaks + Replaces is not supposed to be used on virtual packages:
http://www.chiark.greenend.org.uk/doc/debian-policy/policy.html/ch-relationships.html#s7.6.1

| For this usage of Replaces, virtual packages (see Virtual packages - Provides, 
| Section 7.5) are not considered when looking at a Replaces field. The packages 
| declared as being replaced must be mentioned by their real names.

Maybe that's why Apt is confused in this multi-arch configuration.


Note that, based on 7.6.2, the usual pattern for virtual packages would be 
Provides + Conflicts + Replaces:

|  In this situation, the package declared as being replaced can be a virtual 
|  package, so for example, all mail transport agents (MTAs) would have the 
|  following fields in their control files:
|
|     Provides: mail-transport-agent
|     Conflicts: mail-transport-agent
|     Replaces: mail-transport-agent
|
| ensuring that only one MTA can be unpacked at any one time

Seems like something to try to see if it fixes the issue.


-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libitalccore depends on:
ii  dpkg             1.19.0.5
ii  libc6            2.27-3
ii  libgcc1          1:8-20180425-1
ii  libjpeg62-turbo  1:1.5.2-2+b1
ii  libpng16-16      1.6.34-1
ii  libqt5core5a     5.10.1+dfsg-5
ii  libqt5gui5       5.10.1+dfsg-5
ii  libqt5network5   5.10.1+dfsg-5
ii  libqt5widgets5   5.10.1+dfsg-5
ii  libqt5xml5       5.10.1+dfsg-5
ii  libssl1.1        1.1.0h-2
ii  libstdc++6       8-20180425-1
ii  zlib1g           1:1.2.8.dfsg-5

libitalccore recommends no packages.

libitalccore suggests no packages.

-- no debconf information