[Bug]: flatpak-session-helper is not stopped when logging out of the desktop session

[bertogg]

Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a bug that matches the one I want to file, without success.
• If this is an issue with a particular app, I have tried filing it in the appropriate issue tracker for the app (e.g. under https://github.com/flathub/) and determined that it is an issue with Flatpak itself.
• This issue is not a report of a security vulnerability (see here if you need to report a security issue).

Flatpak version

1.12.4

What Linux distribution are you using?

Arch Linux

Linux distribution version

No response

What architecture are you using?

x86_64

How to reproduce

In some cases flatpak-session-helper can stay alive after the graphical session has been closed.

If a new graphical session is started afterwards and has a different value for DISPLAY or XAUTHORITY (as is the case with SDDM) then the helper's HostCommand method can fail to run programs. The problem disappears if the user kills or restarts the flatpak-session-helper process.

The GNOME session works around this problem by restarting dbus on shutdown, thus ensuring that the new desktop session will have a new instance of the flatpak-session-helper.

Making the Flatpak session helper PartOf=graphical-session.target kills it when the session is closed and fixes this problem.

Expected Behavior

After running a Flatpak application and then closing the graphical session the flatpak-session-helper process is killed automatically.

Actual Behavior

The flatpak-session-helper process stays alive if DBus is not restarted.

Additional Information

The same problem was found with xdg-desktop-portal and fixed earlier this year: flatpak/xdg-desktop-portal#801

[bertogg]

I think flatpak-portal should have the same treatment