From 21ab17debeab844336d2c064471ba984200b3c8a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sandro=20J=C3=A4ckel?= <sandro.jaeckel@gmail.com>
Date: Sat, 4 May 2024 18:12:54 +0200
Subject: [PATCH] nixos/dbus: fix switching from dbus-broker to dbus

---
 nixos/modules/services/system/dbus.nix               | 12 ++++++++++++
 .../system/activation/switch-to-configuration.pl     |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/nixos/modules/services/system/dbus.nix b/nixos/modules/services/system/dbus.nix
index 8dba0aca6433..26f4eba707f9 100644
--- a/nixos/modules/services/system/dbus.nix
+++ b/nixos/modules/services/system/dbus.nix
@@ -147,6 +147,10 @@ in
       };
 
       systemd.services.dbus = {
+        aliases = [
+          # hack aiding to prevent dbus from restarting when switching from dbus-broker back to dbus
+          "dbus-broker.service"
+        ];
         # Don't restart dbus-daemon. Bad things tend to happen if we do.
         reloadIfChanged = true;
         restartTriggers = [
@@ -158,6 +162,10 @@ in
       };
 
       systemd.user.services.dbus = {
+        aliases = [
+          # hack aiding to prevent dbus from restarting when switching from dbus-broker back to dbus
+          "dbus-broker.service"
+        ];
         # Don't restart dbus-daemon. Bad things tend to happen if we do.
         reloadIfChanged = true;
         restartTriggers = [
@@ -184,6 +192,8 @@ in
       # https://github.com/NixOS/nixpkgs/issues/108643
       systemd.services.dbus-broker = {
         aliases = [
+          # allow other services to just depend on dbus,
+          # but also a hack aiding to prevent dbus from restarting when switching from dbus-broker back to dbus
           "dbus.service"
         ];
         unitConfig = {
@@ -203,6 +213,8 @@ in
 
       systemd.user.services.dbus-broker = {
         aliases = [
+          # allow other services to just depend on dbus,
+          # but also a hack aiding to prevent dbus from restarting when switching from dbus-broker back to dbus
           "dbus.service"
         ];
         # Don't restart dbus. Bad things tend to happen if we do.
diff --git a/nixos/modules/system/activation/switch-to-configuration.pl b/nixos/modules/system/activation/switch-to-configuration.pl
index ba45231465fb..cabc1dcc2d65 100755
--- a/nixos/modules/system/activation/switch-to-configuration.pl
+++ b/nixos/modules/system/activation/switch-to-configuration.pl
@@ -472,6 +472,9 @@ sub handle_modified_unit { ## no critic(Subroutines::ProhibitManyArgs, Subroutin
             $units_to_reload->{$unit} = 1;
             record_unit($reload_list_file, $unit);
         }
+        elsif ($unit eq "dbus.service" || $unit eq "dbus-broker.service") {
+            # dbus service should only ever be reloaded, not started/stoped/restarted as that would break the system.
+        }
         elsif (!parse_systemd_bool(\%new_unit_info, "Service", "X-RestartIfChanged", 1) || parse_systemd_bool(\%new_unit_info, "Unit", "RefuseManualStop", 0) || parse_systemd_bool(\%new_unit_info, "Unit", "X-OnlyManualStart", 0)) {
             $units_to_skip->{$unit} = 1;
         } else {