cups-control is missing from connections list

[Peter Petrakis]

In the process of figuring out why brave doesn't print. I followed this guide to inform me how snaps work.

https://tutorials.ubuntu.com/tutorial/advanced-snap-usage#3

(cups-control actually shows up in this list)

I was intuitively looking for services named "lpr", or "printing", or something with the string "cups" in it. However on my 18.04 system, cups doesn't show up as an available connection.

ppetraki@vanguard:~/Sandbox/graphics$ snap connections | grep cups

It was only until after I knew what the answer looked like was I able to allow brave to print.

https://askubuntu.com/questions/886488/application-installed-as-snap-package-cant-see-printer/1167368#1167368

Now "cups-control" shows up as an option since I've made the connection.

ppetraki@vanguard:~/Sandbox/graphics$ snap connections | grep cups
cups-control brave:cups-control :cups-control manual

How is someone supposed to be able to reason their way through the problem if snapd is hiding the very connections you need to do the job?

[Paweł Stołowski (stolowski)]

'snap connections' only shows connected interfaces in the system (skips unconnected ones of the system, even if --all flag is given).

However, if you give it brave as an argument, it gives a hint:

$ snap connections brave
Interface Plug Slot Notes
content[icon-themes] brave:icon-themes gtk-common-themes:icon-themes -
content[sound-themes] brave:sound-themes gtk-common-themes:sound-themes -
cups-control brave:cups-control - -
...

It also reports cups-control as potential candidate if you say '--all', which also reports unconnected slots of all installed snaps:

$ snap connections --all
Interface Plug Slot Notes
avahi-observe brave:avahi-observe - -
browser-support brave:browser-sandbox :browser-support -
camera brave:camera - -
content - gtk-common-themes:gtk-2-themes -
content[gtk-3-themes] brave:gtk-3-themes gtk-common-themes:gtk-3-themes -
cups-control brave:cups-control - -
.....

I think what we're missing is a better help from 'snap connections --help'. Without brave installed in this example, the only way to learn about cups-control in the system is with 'snap connections system' ('snap connections --all' hides unconnected system slots by design), or with 'snap interfaces' (which is still present but deprecated).