cmus: add mpris support on linux

[aanderse]

Motivation for this change

#56813

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

---

[aanderse]

@GrahamcOfBorg build cmus

[aanderse]

ping @oxij as the listed maintainer.

[oxij]

`systemd`? Shouldn't it be `dbus` or something? Also please make this thing optional.

[oxij]

Also, a minor nitpick, verbs in commit messages should be written in the present imperative tense, not in the past tense: "add/init/make/etc <something>", not "added/?/made <something>".

[aanderse]

@oxij Looks like systemd from the Makefile: https://github.com/cmus/cmus/blob/967a470b31ed2e6fc737ae523ba24b4dfdf81595/Makefile#L25

No need to make optional as systemd is a hard dependency on Linux.

[oxij]

No need to make optional as systemd is a hard dependency on Linux.

IMHO "optional dependency" means "can be built without it and the binary will still work" which means that since both questions "can it be built without it? will it still work?" have positive answers on Linux this dependency must be made optional even on Linux. In other words, Linux kernel does not imply systemd init daemon (e.g. I run Linux without anything systemd-related on my system) hence it must be made optional. Given the current attitude towards systemd by nixpkgs I'm not against setting it to `isLinux` by default, though.

Looks like systemd from the Makefile: https://github.com/cmus/cmus/blob/967a470b31ed2e6fc737ae523ba24b4dfdf81595/Makefile#L24

I see, MPRIS is just a `dbus` interface so depending on the whole of `systemd` for that seems strange to me, but I assume upstream knows better, okay. (But if I cared about that feature I would have checked if it could be built with `dbus` libs only too. `dbus` does not imply `systemd` either.)

[aanderse]

Good point.

My understanding of MPRIS was also that the communication happened over dbus, but again it looks like you can (and cmus does) use libsystemd: https://github.com/cmus/cmus/blob/483d1862ed023c3e00f2c8c4e71da40022af2f78/configure#L584

I've made the dependency optional via mprisSupport and cleaned up a bit. How does this look to you?

[oxij]

Yep, LGTM. Thanks! @7c6f434c, could you merge this please?

[Mic92]

@GrahamcOfBorg build cmus

[aanderse]

cmus was already not building on darwin it appears: https://hydra.nixos.org/eval/1508607?filter=cmus&compare=1508574&full=#tabs-still-fail

@Mic92 Look good to merge?