It is. nautilus has:

Recommends:     glycin-thumbnailer%{_isa}

PackageKit or dnf should install Recommends on upgrade, yes?

I had to manually install it and other people are reporting the same thing:
- https://duckduckgo.com/?t=fpas&q=glycin-thumbnailer+fedora+43+reddit&ia=web
- https://duckduckgo.com/?q=thumbnails+%22fedora+43%22+&t=fpas&ia=web

might be a good idea to write for known issues blog post/forum post or such

@ngompa thinks this is a bug in PackageKit or dnf: Recommends are supposed to be installed on upgrade if the Recommends is new. He has recommended use of conditional dependencies.

We should also add this dependency to comps (which I will do now), but that may not be enough because Neal says that is broken too (new comps packages are supposed to be installed on upgrade, but apparently are not?).

It is already present in comps. :(

Neal mentioned this problem is fixed in PackageKit's dnf5 backend, but that's not going to do any good for users who are already missing the package.

We'll probably need to add a conditional Requires. The easiest such condition would be: use Requires for Fedora 43 or 44 (since we support skipping one version during upgrade), and use Recommends for Fedora 45 and above.

This is what I'd recommend:

%if 0%{?fedora} && 0%{?fedora} <= 45
Requires:       (glycin-thumbnailer%{_isa} or ffmpeg-thumbnailer%{?_isa})
Suggests:       glycin-thumbnailer%{_isa}
%else
Recommends:     glycin-thumbnailer%{_isa}
%endif

Red Hat Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2426436

We have two problems here:

• New Recommends not installed on upgrade. I think we need to either (a) altogether stop using Recommends in Fedora, because in current form it tricks packagers into thinking the package will be installed even though it won't, or (b) change the behavior of dnf. I've been unable to find any reference stating the expected behavior for dnf upgrades, only for new installs, but if new Recommends are not respected on upgrade then we basically always have to use Requires, and that surely does not make sense, so it must be a bug. Right? We would have to literally replace all Recommends with Requires if not changed.
• New comps package not installed on upgrade. I suppose this also requires a dnf bug report? Historically, we knew that comps was only for fresh installs and not for upgrades, but that changed at some point in the past and we have more recently been relying on it.

@ngompa would you be willing to help create bug reports for this, since you're especially familiar with dnf?

We can see how that bug report goes and add your proposed workaround to the spec file if the dnf maintainers do not agree.

Is there any reason not to just add the requires in F43 so it's not broken anymore? I had been wondering for months why it was broken before I took the time to root cause the problem. Less savvy users will just reinstall, or install another distribution.

The "Recommends" also makes no sense when prior to F43 the thumbnailer was part of the library so always installed.

Yes, we should do that as well. I just haven't gotten around to it yet. Feel free.

The "Recommends" also makes no sense when prior to F43 the thumbnailer was part of the library so always installed.

If not for this problem, it would make sense. Thumbnailers should be optional: always present by default, but removable for users who choose to do so. E.g. some users want to use ffmpeg-thumbnailer instead.

New Recommends not installed on upgrade.

The Recommends were simply never actually added, see https://bugzilla.redhat.com/show_bug.cgi?id=2426436. And that's my fault, since I am the developer who attempted to add them. Sorry. Presumably it will work with this fixed?

That leaves comps as a problem, though.

For me the problem is fixed with this nautilus change:

I'm not sure what your expectations were with comps changes, but, to me, it's always been clear that comps was only useful for installations, and that we always needed to have another solution for upgrades, that solution being dependencies (or weak dependencies).

That was true until a just a few years ago, but sometime more recently dnf has started updating comps groups as well. Apparently that no longer works.

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/workstation/tickets/issues/494

Please continue any further discussion there.