No warning/error when removing dependency

[Michi Henning]

Our thumbnailer snap uses ubuntu-app-platform. With the thumbnailer snap installed and connected, I can remove ubuntu-app-platform without any problems whatsoever:

$ sudo snap remove ubuntu-app-platform
ubuntu-app-platform removed
$

That doesn't look like a good idea to me because I may not know that there are other snaps that I have just broken by mistake.

I do find out that I've done something wrong once I try to run our service:

$ thumbnailer.thumbnailer-service &
[2] 10587
michi@djembefola:~/src/thumbnailer/gstreamer-plugins$ You need to connect the ubuntu-app-platform package with your application
to reuse shared assets, please run:
snap install ubuntu-app-platform
snap connect thumbnailer:platform ubuntu-app-platform:platform

[2]- Exit 1 thumbnailer.thumbnailer-service

That's a nice error message, and it is very clear. But, unfortunately, it's too late. I might remove a snap and then not find out for weeks that I've broken something else...

I think I should get an error when I try to remove a snap that other snaps depend on. Maybe, if I want to insist on breaking things, a --force option could be used to let me live dangerously.

But, overall, I think it would be best to have something similar to apt, which tells me that, if I want to remove X, it'll also remove Y, Z if they depend on X.

[Michi Henning (michihenning)]

I just noticed that I can also install thumbnailer without ubuntu-app-platform being installed first. There is no error, even though there is no way that thumbnailer will work that way.

It seems that installing a snap should automatically install all the snaps it depends on. Without this, I only find out at run time when my service fails to start that a dependency is missing.