Questions on upgrading the FreeCAD snap to core24

[furgo]

We’re in the process of upgrading the FreeCAD snap to core24. The contributor who originally created the snap around 2018 did an excellent job but is no longer active. While reviewing which parts of the snapcraft.yaml are no longer needed, there were two snippets that came across as workarounds for features not implemented at the time. I’m wondering if they can be removed.

The foo-install-cups plug

The first one is this foo-install-cups plug:

FreeCAD/FreeCAD-snap/blob/5bf941306cbd90928e0358a79e4560d090962996/snap/snapcraft.yaml#L64-L70

I found a reference to this post from over 2 years ago:

The "cups" Interface

Introduction The cups interface should be plugged by all Snaps of software which prints, like LibreOffice, Chrome/Chromium, Firefox, Thunderbird, DarkTable, RawTherapee, … It allows them to print via CUPS but it blocks any administrative CUPS operations (like creating or modifying print queues or accessing other user’s jobs). Before the cups interface was introduced, you had to plug the cups-control interface for this, but as this interface does not only allow to list the available printers an…

Which states:

Note: Having to add these lines is only a temporary workaround. The default-provider functionality is planned to be added to the cups interface in snapd in the coming months.

My question is: has this functionality already been added to the cups interface? Can this plug be removed or rewritten in another way?

Stub chown

This part is defined here:

FreeCAD/FreeCAD-snap/blob/5bf941306cbd90928e0358a79e4560d090962996/snap/snapcraft.yaml#L135-L143

To build this source code here:

FreeCAD/FreeCAD-snap/blob/5bf941306cbd90928e0358a79e4560d090962996/snap/local/stub-chown/stub-chown.c#L1-L10

I could not find any reference to other snaps needing to build this chown stub. Neither how it’s used in the FreeCAD snap.

I’d like to understand its purpose. Perhaps someone more experienced in snaps has some feedback?

In any case, if someone more experienced with snaps wants to do a quick review of that PR and the snapcraft.yaml file in it, help from expert snapcrafters would be really appreciated. FreeCAD used to be one of the featured snaps in the App Store and it still is featured under the Art and Design apps banner, so it would be great for us to be able to provide a great experience to users.

Thanks!

[scarlettmoore]

AFAIK the cups one is still needed. Not sure about the other one.

[furgo]

Thank you (and for your help with this upgrade so far!). The first thing I noticed was that from a GitHub search Code search results · GitHub only 25 results were returned (some of which from FreeCAD forks). That and the note on that old forum post made me think that it might no longer be needed. But perhaps it still is and there are not many snaps that need the cups snap.

@till.kamppeter, you wrote the referenced forum post. Would you have more context? Thanks!