fix(system-manager): remove evaluation-time package reads

Assisted-by: pi (gpt-5.6-sol)

hosts/ubuntu/common/global/default.nix

@@ -4,11 +4,12 @@
   pkgs,
   ...
 }: let
-  dbusSessionConfig =
-    builtins.replaceStrings
-    ["<include ignore_missing=\"yes\">/etc/dbus-1/session.conf</include>"]
-    [""]
-    (builtins.readFile "${pkgs.dbus}/share/dbus-1/session.conf");
+  dbusSessionConfig = pkgs.runCommandLocal "dbus-session.conf" {} ''
+    substitute ${pkgs.dbus}/share/dbus-1/session.conf "$out" \
+      --replace-fail \
+      '<include ignore_missing="yes">/etc/dbus-1/session.conf</include>' \
+      ""
+  '';
 in {
   imports =
     [
@@ -28,7 +29,7 @@ in {
   # Nix's D-Bus tools use /etc for their primary config, while Ubuntu keeps the
   # defaults in /usr/share and reserves /etc for local includes. Remove the
   # self-include when installing those defaults into /etc.
-  environment.etc."dbus-1/session.conf".text = dbusSessionConfig;
+  environment.etc."dbus-1/session.conf".source = dbusSessionConfig;
 
   # The management CLI on the system PATH (/run/system-manager/sw/bin), like
   # nixos-rebuild on NixOS, so switching doesn't need `nix run`.

hosts/ubuntu/electra/default.nix

@@ -11,5 +11,9 @@
   # Pinned rather than auto-detected: with an empty list the upstream module
   # installs a udev rule that calls /run/current-system/systemd/bin/systemctl,
   # a path that does not exist outside NixOS.
-  networking.wireless.interfaces = ["wlp0s20f3"];
+  networking.wireless = {
+    # system-manager lacks the NixOS D-Bus module that installs its policy.
+    dbusControlled = false;
+    interfaces = ["wlp0s20f3"];
+  };
 }

modules/system-manager/wireless.nix

@@ -3,9 +3,9 @@
 #
 # system-manager reuses nixpkgs' systemdUtils, environment.etc and userborn, so
 # the unit, the generated wpa_supplicant.conf and the wpa_supplicant user all
-# come out unchanged. Only a handful of NixOS-only options are missing: three
-# are read but never acted on, and the two that do matter are re-expressed on
-# top of environment.etc, which the host distro reads from the same paths.
+# come out unchanged. Only a handful of NixOS-only options are missing: four
+# are read but never acted on, and the udev rules are re-expressed on top of
+# environment.etc, which the host distro reads from the same path.
 {
   config,
   lib,
@@ -51,19 +51,7 @@ in {
     };
   };
 
-  config = {
-    environment.etc = lib.mkMerge [
-      (lib.mkIf (cfg.udev.extraRules != "") {
-        "udev/rules.d/99-system-manager.rules".text = cfg.udev.extraRules;
-      })
-      # The attribute name may not carry string context, hence the discard; the
-      # value keeps its reference to the store path.
-      (lib.listToAttrs (map (file: {
-          name = "dbus-1/system.d/" + builtins.unsafeDiscardStringContext (baseNameOf file);
-          value = {source = file;};
-        })
-        (lib.concatMap (pkg: lib.filesystem.listFilesRecursive "${pkg}/share/dbus-1/system.d")
-          (lib.filter (pkg: builtins.pathExists "${pkg}/share/dbus-1/system.d") cfg.dbus.packages))))
-    ];
+  config = lib.mkIf (cfg.udev.extraRules != "") {
+    environment.etc."udev/rules.d/99-system-manager.rules".text = cfg.udev.extraRules;
   };
 }