feat(systemd-notify): allow multiple failure scripts

modules/nixos/systemd-notify.nix

@@ -6,44 +6,44 @@
 
 let
   inherit (lib)
-    mkEnableOption
-    mkIf
+    getExe
+    mapAttrs'
+    mapAttrsToList
     mkOption
     mkForce
-    optional
+    nameValuePair
     ;
-  inherit (lib.types) attrsOf str submodule;
+  inherit (lib.types) attrsOf package submodule;
 
   cfg = config.services.systemd-notify;
 in
 
 {
-  options.services.systemd-notify = {
-    enable = mkEnableOption "notifications when a systemd unit fails.";
-
-    command = mkOption {
-      type = str;
-      description = ''
-        Command to run on failure of a systemd unit.
-        Takes the name of the failed unit as an argument.
-      '';
-    };
+  options.services.systemd-notify = mkOption {
+    type = attrsOf package;
+    description = ''
+      Commands to execute when a systemd unit fails.
+      Attrs keys will be the unit name and attrs value is the command that
+      will be run with the name of the failed unit as an argument.
+    '';
+    default = { };
   };
 
   options.systemd.services = mkOption {
     type = attrsOf (submodule {
-      config.onFailure = optional cfg.enable "email@%n.service";
+      config.onFailure = mapAttrsToList (name: _: "${name}@%n.service") cfg;
     });
   };
 
-  config = mkIf cfg.enable {
-    systemd.services."email@" = {
-      description = "Sends a status mail via sendmail on service failures.";
+  config.systemd.services = mapAttrs' (
+    name: script:
+    nameValuePair "${name}@" {
+      description = "Run ${name} script on service failures.";
       onFailure = mkForce [ ]; # Avoid recursive failures
       serviceConfig = {
-        ExecStart = "${cfg.command} %i";
+        ExecStart = "${getExe script} %i";
         Type = "oneshot";
       };
-    };
-  };
+    }
+  ) cfg;
 }