fluidsynth: add sound service option

Fluidsynth's systemd unit currently has a hard dependency on the
pulseaudio systemd service. Since fluidsynth can use other sound
services (e.g., pipewire-pulse), this should be configurable. This
commit adds the relevant option.

PR #2238

modules/services/fluidsynth.nix

@@ -21,6 +21,15 @@ in {
         '';
       };
 
+      soundService = mkOption {
+        type = types.enum [ "jack" "pipewire-pulse" "pulseaudio" ];
+        default = "pulseaudio";
+        example = "pipewire-pulse";
+        description = ''
+          The systemd sound service to depend on.
+        '';
+      };
+
       extraOptions = mkOption {
         type = types.listOf types.str;
         default = [ ];
@@ -46,8 +55,8 @@ in {
       Unit = {
         Description = "FluidSynth Daemon";
         Documentation = "man:fluidsynth(1)";
-        BindsTo = [ "pulseaudio.service" ];
-        After = [ "pulseaudio.service" ];
+        BindsTo = [ (cfg.soundService + ".service") ];
+        After = [ (cfg.soundService + ".service") ];
       };
 
       Install = { WantedBy = [ "default.target" ]; };

tests/modules/services/fluidsynth/service.nix

@@ -1,6 +1,7 @@
 { config, pkgs, ... }: {
   config = {
     services.fluidsynth.enable = true;
+    services.fluidsynth.soundService = "pipewire-pulse";
     services.fluidsynth.soundFont = "/path/to/soundFont";
     services.fluidsynth.extraOptions = [ "--sample-rate 96000" ];
 
@@ -19,6 +20,12 @@
 
       assertFileContains $serviceFile \
         'ExecStart=@fluidsynth@/bin/fluidsynth -a pulseaudio -si --sample-rate 96000 /path/to/soundFont'
+
+      assertFileContains $serviceFile \
+        'After=pipewire-pulse.service'
+
+      assertFileContains $serviceFile \
+        'BindsTo=pipewire-pulse.service'
     '';
   };
 }