systemd: add a name option to all systemd units

This allows us to set things like dependencies in a way that we can
catch typos at eval time.
So instead of
```nix
systemd.services.foo.wants = [ "bar.service" ];
```
we can write
```nix
systemd.services.foo.wants = [ config.systemd.services.bar.name ];
```
which will throw an error if no such service has been defined.

Not all cases can be done like this (eg template services), but in a lot
of cases this will allow to avoid typos.

There is a matching option on the unit option
(`systemd.units."foo.service".name`) as well.

1 files changed, 11 insertions, 2 deletions

diff --git a/nixos/tests/systemd.nix b/nixos/tests/systemd.nix
index 1a39cc73c8868..4b087d403f37d 100644
--- a/nixos/tests/systemd.nix
+++ b/nixos/tests/systemd.nix
@@ -1,7 +1,7 @@
 import ./make-test-python.nix ({ pkgs, ... }: {
   name = "systemd";
 
-  nodes.machine = { lib, ... }: {
+  nodes.machine = { config, lib, ... }: {
     imports = [ common/user-account.nix common/x11.nix ];
 
     virtualisation.emptyDiskImages = [ 512 512 ];
@@ -38,9 +38,18 @@ import ./make-test-python.nix ({ pkgs, ... }: {
       script = "true";
     };
 
+    systemd.services.testDependency1 = {
+      description = "Test Dependency 1";
+      wantedBy = [ config.systemd.services."testservice1".name ];
+      serviceConfig.Type = "oneshot";
+      script = ''
+        true
+      '';
+    };
+
     systemd.services.testservice1 = {
       description = "Test Service 1";
-      wantedBy = [ "multi-user.target" ];
+      wantedBy = [ config.systemd.targets.multi-user.name ];
       serviceConfig.Type = "oneshot";
       script = ''
         if [ "$XXX_SYSTEM" = foo ]; then