Bug 2209402

Do I understand correctly that dnf5 package will provide /usr/bin/dnf program? In other words, the official interface will be a dependency on dnf5 and execution of dnf?

If it is so, adapting perl-CPAN-Plugin-Sysdeps has to wait on the dfn5 change. If I adapted perl-CPAN-Plugin-Sysdeps sooner, it would execute nonexistent "dnf" command because until then dnf5 package won't provide dnf executable.

To explain my question: Should we start telling users and upstreams that instead of executing "dnf" they should execute "dnf5" program?

> Do I understand correctly that dnf5 package will provide /usr/bin/dnf program? In other words, the official interface will be a dependency on dnf5 and execution of dnf?

Correct!

> Should we start telling users and upstreams that instead of executing "dnf" they should execute "dnf5" program?

No, although for a little while, software may want to support both DNF 4 and DNF 5 in the same codebase. The command-line interface between DNF 4 and 5 is slightly different, so it may be desirable to explicitly call /usr/bin/dnf5 in some cases to avoid ambiguity. But the typical command-line user should keep executing `dnf` and hopefully will not even notice much of a difference after /usr/bin/dnf becomes DNF 5.

> If it is so, adapting perl-CPAN-Plugin-Sysdeps has to wait on the dfn5 change. If I adapted perl-CPAN-Plugin-Sysdeps sooner, it would execute nonexistent "dnf" command because until then dnf5 package won't provide dnf executable.

Yes, the change is not quite yet released to Rawhide; there have been a couple hiccups getting there. What's important is that your package does not depend on `dnf` in Fedora >= 39. An immediate fix would be to depend on `python3-dnf` and call /usr/bin/dnf-3 instead of `dnf`.

If you want to implement support for DNF 5, and support DNF 4 and DNF 5 in the same version of the package, I recommend the following:
- Add a conditional statement to the spec file to require DNF 4 in Fedora <= 38 and DNF 5 in other versions:
```
%if 0%{?fedora} <= 38
Requires: python3-dnf
%else
Requires: dnf5
%endif
```
- Then, if your package can use the same command-line invocation to call both DNF 4 and DNF 5, you may not need to change any code, simply keep calling `dnf`. But if some behavior you need has changed since DNF 5, you will need to detect whether the system is using DNF 4 or 5 (you can check whether /usr/bin/dnf5 exists) and call the correct command accordingly, either /usr/bin/dnf5 or, if only DNF 4 is available, /usr/bin/dnf-3.

If instead you find that your program needs some behavior that isn't (yet) supported by DNF 5, please file an issue in our upstream bug tracker: https://github.com/rpm-software-management/dnf5/issues. Until it's addressed, you'll want to continue using DNF 4, so you should change any calls to "dnf" in your code to "dnf-3", and change your spec file to depend on python3-dnf instead of dnf in all versions of Fedora.

Let me know if you have further questions, I understand it's a confusing situation.

Thanks for confirming DNF5 interface.

> What's important is that your package does not depend on `dnf` in Fedora >= 39.

That's what I have a problem with. With the time line.

> %if 0%{?fedora} <= 38
> Requires: python3-dnf
> %else
> Requires: dnf5
> %endif
>
> - Then, if your package can use the same command-line invocation to call both DNF 4 and DNF 5, you may not need to change any code, simply keep calling `dnf`.

That's not good advise because on old Fedoras:

$ rpm -qf /usr/bin/dnf
dnf-4.15.1-1.fc37.noarch

and now on F39:

# rpm -qf /usr/bin/dnf
dnf-4.15.1-1.fc39.noarch

In my opinion, the real condition is not "Fedora >= 39". It is "/usr/bin/dnf is provided by dnf5 package". Packagers are not going to change their packages now, and then few weeks later after you make DNF5 default.

I guess once dnf5 package provides /usr/bin/dnf5, it will also provide "dnf" RPM symbol. Hence I propose a different approach: Keep packages as they are (invoke /usr/bin/dnf and depend on dnf). Once DNF5 is default, packagers can gradually change the dependency from "dnf" to "dnf5". Preferably before F39 freeze.

> In my opinion, the real condition is not "Fedora >= 39". It is "/usr/bin/dnf is provided by dnf5 package". Packagers are not going to change their packages now, and then few weeks later after you make DNF5 default.

Yes, you're right, I should have clarified that those changes will have to wait until DNF 5 provides /usr/bin/dnf. 

> I guess once dnf5 package provides /usr/bin/dnf5, it will also provide "dnf" RPM symbol. Hence I propose a different approach: Keep packages as they are (invoke /usr/bin/dnf and depend on dnf). Once DNF5 is default, packagers can gradually change the dependency from "dnf" to "dnf5". Preferably before F39 freeze.

I think the issue with that is that when DNF 5 takes over /usr/bin/dnf, programs that call the binary could break since the command-line interface will change. So they should immediately switch to calling /usr/bin/dnf-3 and depending on python3-dnf so that they won't sponteneously break, and then later they can figure out support for DNF 5.

But yes, I agree, it's awkward to ask maintainers to change their packages twice.

Reverted in perl-CPAN-Plugin-Sysdeps-0.70-11.fc39 because DNF5 is not ready yet.
This request will be revisited in Fedora 41.

This bug appears to have been reported against 'rawhide' during the Fedora Linux 39 development cycle.
Changing version to 39.

The Fedora 41 development cycle is beginning, and we are planning to obsolete DNF 4 by DNF 5 in Fedora Rawhide within the next few weeks. Again, libdnf is not going away, and the old DNF 4 command will still be available as `/usr/bin/dnf-3`, but `/usr/bin/dnf` will be DNF 5, which has a slightly different command-line interface. Packages should no longer depend on the `dnf` package in Fedora 41+.

Thanks for the reminder. I hope you will tell us when dnf5 starts providing /usr/bin/dnf program. Until then I cannot implement this change because this package executes /usr/bin/dnf.