Fix reload for services without reload functionality.

examples/example.nix

@@ -1,4 +1,4 @@
-{ lib, pkgs, ... }: {
+{ lib, ... }: {
   config = {
     nixpkgs.hostPlatform = "x86_64-linux";
 
@@ -62,7 +62,6 @@
               serviceConfig = {
                 Type = "oneshot";
                 RemainAfterExit = true;
-                ExecReload = "${lib.getBin pkgs.coreutils}/bin/true";
               };
               wantedBy = [ "system-manager.target" ];
               requiredBy = lib.mkIf (ix > 5) [ "service-0.service" ];

src/activate/services.rs

@@ -89,7 +89,7 @@ pub fn activate(
     wait_for_jobs(
         &service_manager,
         &job_monitor,
-        reload_units(&service_manager, convert_services(&services_to_reload))
+        reload_or_restart_units(&service_manager, convert_services(&services_to_reload))
             + start_units(&service_manager, ["system-manager.target"]),
         &timeout,
     )
@@ -229,12 +229,15 @@ where
     for_each_unit(|s| service_manager.stop_unit(s), units.as_ref(), "stopping")
 }
 
-fn reload_units<'a, U>(service_manager: &systemd::ServiceManager, units: U) -> HashSet<JobId>
+fn reload_or_restart_units<'a, U>(
+    service_manager: &systemd::ServiceManager,
+    units: U,
+) -> HashSet<JobId>
 where
     U: AsRef<[&'a str]>,
 {
     for_each_unit(
-        |s| service_manager.reload_unit(s),
+        |s| service_manager.reload_or_restart_unit(s),
         units.as_ref(),
         "reloading",
     )

src/systemd.rs

@@ -235,9 +235,13 @@ impl ServiceManager {
         Ok(true)
     }
 
-    pub fn reload_unit(&self, unit_name: &str) -> Result<Job, Error> {
+    pub fn reload_or_restart_unit(&self, unit_name: &str) -> Result<Job, Error> {
         Ok(Job {
-            path: OrgFreedesktopSystemd1Manager::reload_unit(&self.proxy, unit_name, "replace")?,
+            path: OrgFreedesktopSystemd1Manager::reload_or_restart_unit(
+                &self.proxy,
+                unit_name,
+                "replace",
+            )?,
         })
     }
 

test/nix/modules/default.nix

@@ -6,8 +6,44 @@
 let
   forEachUbuntuImage = lib.flip lib.mapAttrs' system-manager.lib.images.ubuntu.${system};
 
+  # To test reload and restart, we include two services, one that can be reloaded
+  # and one that cannot.
+  # The id parameter is a string that can be used to force reloading the services
+  # between two configs by changing their contents.
+  testModule = id: { lib, pkgs, ... }: {
+    systemd.services = {
+      has-reload = {
+        enable = true;
+        description = "service-reload";
+        serviceConfig = {
+          Type = "oneshot";
+          RemainAfterExit = true;
+          ExecReload = ''
+            ${lib.getBin pkgs.coreutils}/bin/true
+          '';
+        };
+        wantedBy = [ "system-manager.target" ];
+        script = ''
+          echo "I can be reloaded (id: ${id})"
+        '';
+      };
+      has-no-reload = {
+        enable = true;
+        description = "service-no-reload";
+        serviceConfig.Type = "simple";
+        wantedBy = [ "system-manager.target" ];
+        script = ''
+          while true; do
+            echo "I cannot be reloaded (id: ${id})"
+          done
+        '';
+      };
+    };
+  };
+
   newConfig = system-manager.lib.makeSystemConfig {
     modules = [
+      (testModule "new")
       ({ lib, pkgs, ... }: {
         config = {
           nixpkgs.hostPlatform = system;
@@ -22,18 +58,20 @@ let
             };
           };
 
-          systemd.services.new-service = {
-            enable = true;
-            description = "new-service";
-            serviceConfig = {
-              Type = "oneshot";
-              RemainAfterExit = true;
-              ExecReload = "${lib.getBin pkgs.coreutils}/bin/true";
+          systemd.services = {
+            new-service = {
+              enable = true;
+              description = "new-service";
+              serviceConfig = {
+                Type = "oneshot";
+                RemainAfterExit = true;
+                ExecReload = "${lib.getBin pkgs.coreutils}/bin/true";
+              };
+              wantedBy = [ "system-manager.target" "default.target" ];
+              script = ''
+                sleep 2
+              '';
             };
-            wantedBy = [ "system-manager.target" "default.target" ];
-            script = ''
-              sleep 2
-            '';
           };
         };
       })
@@ -55,6 +93,7 @@ forEachUbuntuImage
             nodes = {
               node1 = { config, ... }: {
                 modules = [
+                  (testModule "old")
                   ../../../examples/example.nix
                 ];