Snap accumulates content interface connections to multiple platform snaps

snapd
1

A strange case: kdenlive does not start and complains (on the console):

Cannot mix incompatible Qt library (5.15.3) with this library (5.15.2)

But how can that be? It uses the kde-neon extension, and its platform snap will surely not contain mixed Qt versions. Let’s check:

$ ls -al /snap/kdenlive/46/usr/lib/x86_64-linux-gnu/libQt5NetworkAuth.so.5
lrwxrwxrwx 1 root root 27 Mai 25 13:50 /snap/kdenlive/46/usr/lib/x86_64-linux-gnu/libQt5NetworkAuth.so.5 -> libQt5NetworkAuth.so.5.15.3

$ ls -al /snap/kdenlive/46/kf5/usr/lib/x86_64-linux-gnu/libQt5Multimedia.so.5
lrwxrwxrwx 1 root root 26 Dez  4  2020 /snap/kdenlive/46/kf5/usr/lib/x86_64-linux-gnu/libQt5Multimedia.so.5 -> libQt5Multimedia.so.5.15.2

Ok. It ships one 5.15.3 library that’s not included in the framework. But why does it see 5.15.2 libs? Does it declare the wrong framework plug?

The current version has:

$ grep "kde-framework" /snap/kdenlive/46/meta/snap.yaml 
  kde-frameworks-5-plug:
    content: kde-frameworks-5-qt-5-15-3-core20-all
    default-provider: kde-frameworks-5-qt-5-15-3-core20

But the connections show something very interesting:

$ snap connections kdenlive
Interface                                       Plug                            Slot                                                                      Notes
audio-playback                                  kdenlive:audio-playback         :audio-playback                                                           -
audio-record                                    kdenlive:audio-record           :audio-record                                                             -
content[icon-themes]                            kdenlive:icon-themes            gtk-common-themes:icon-themes                                             -
content[kde-frameworks-5-qt-5-14-core18-all]    kdenlive:kde-frameworks-5-plug  kde-frameworks-5-qt-5-14-core18:kde-frameworks-5-qt-5-14-core18-slot      -
content[kde-frameworks-5-qt-5-15-3-core20-all]  kdenlive:kde-frameworks-5-plug  kde-frameworks-5-qt-5-15-3-core20:kde-frameworks-5-qt-5-15-3-core20-slot  -
content[kde-frameworks-5-qt-5-15-core20-all]    kdenlive:kde-frameworks-5-plug  kde-frameworks-5-qt-5-15-core20:kde-frameworks-5-qt-5-15-core20-slot      -
content[sound-themes]                           kdenlive:sound-themes           gtk-common-themes:sound-themes                                            -
dbus                                            -                               kdenlive:session-dbus-interface                                           -
desktop                                         kdenlive:desktop                :desktop                                                                  -
desktop-legacy                                  kdenlive:desktop-legacy         :desktop-legacy                                                           -
home                                            kdenlive:home                   :home                                                                     -
network                                         kdenlive:network                :network                                                                  -
network-bind                                    kdenlive:network-bind           :network-bind                                                             -
opengl                                          kdenlive:opengl                 :opengl                                                                   -
removable-media                                 kdenlive:removable-media        :removable-media                                                          -
system-observe                                  kdenlive:system-observe         :system-observe                                                           -
wayland                                         kdenlive:wayland                :wayland                                                                  -
x11                                             kdenlive:x11                    :x11                                                                      -

It has three (!) different framework snaps connected to its “kde-frameworks-5-plug”. So how can that be? Is it possible that those have been steadily accumulated while kdenlive updated its kde-frameworks-5-plug? Shouldn’t obsolete connections be removed if they don’t have matching content attributes?

Edit: @jriddel tells me those might be artefacts from switching between risk levels (e.g. candidate → stable), but isn’t that a supported use-case that shouldn’t break the snap?

I’m most likely missing something important, so please enlighten me. At the very least, the correct platform snap should be mounted as $SNAP/kf5. At the moment, an outdated platform snap gets mounted as $SNAP/kf5 and the current one will get $SNAP/kf5-2 (or an even higher number).

$ snap version
snap    2.53+21.10ubuntu1
snapd   2.53+21.10ubuntu1
series  16
ubuntu  21.10
kernel  5.13.0-20-generic
2

Can you run snap changes kdenlive and attach the output? If snap list --all lists more than one revision of kdenlive, can you check what is the default provider listed in /snap/kdenvlive/<other-rev>/meta/snap.yaml ?

3 
$ snap changes kdenlive
ID    Status  Spawn               Ready               Summary
1546  Done    today at 10:59 CET  today at 11:00 CET  Refresh "kdenlive" snap

$ snap list --all | grep kdenlive
kdenlive                             21.08.2                       45     latest/stable     kde*              disabled
kdenlive                             21.08.3                       46     latest/stable     kde*              -

$ grep kde-framework /snap/kdenlive/45/meta/snap.yaml 
  kde-frameworks-5-plug:
    content: kde-frameworks-5-qt-5-15-3-core20-all
    default-provider: kde-frameworks-5-qt-5-15-3-core20
4

I could reproduce this by first installing kdenlive from stable, and then refreshing it with edge channel. It looks like we have a problem when content interface changes (in this case kde-frameworks-5-plug: the default provider and content tag changed).

As a workaround, removing old frameworks (e.g. kde-frameworks-5-qt-5-14-core18) and leaving only the last one should fix it (but please let me know). This is of course not ideal so this will be investigated, thanks for reporting.

5

Yes. I have another snap (my own, freecad-ppd) that changed its base from core18 to core20, which triggered a change of the default provider (same extension though). It was also connected to two different framework snaps as a consequence on this machine.

That would work, but I still have other snaps depending on that framework. Removing the snap and reinstalling works, but that’s also nothing I’d recommend to new users without a second thought because it loses data in $SNAP_USER_COMMON.

6

Right, that doesn’t work if other snaps use the old framework snaps of course.

7

The gnome extensions avoid this by versioning the plug name itself, not just the content attribute, correct? That could be a simple solution in the short term for the kde-neon extension then.

8

Yes, that’s correct.

9

Alright then: https://github.com/snapcore/snapcraft/pull/3596