bug: Mako onChange hook causes warnings

[kleifgch]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

I am currently using an impermanence-setup for my home directory,
which means that the onChange hook is executed on every boot during the activation via the systemd service.
At this point, the session bus does apparently not yet exist but makoctl tries to use it leading to:

busctl: Failed to set bus address: $DBUS_SESSION_BUS_ADDRESS and $XDG_RUNTIME_DIR not defined (consider using --machine=<user>@.host --user to connect to bus of other user)

My current workaround is

xdg.configFile."mako/config".onChange = let
  dbus-send = "${pkgs.dbus}/bin/dbus-send";
  makoctl = "${config.services.mako.package}/bin/makoctl";
  grep = "${pkgs.gnugrep}/bin/grep";
in lib.mkForce ''
  if [[ -v DBUS_SESSION_BUS_ADDRESS ]]; then
    if ${dbus-send} --print-reply --dest=org.freedesktop.Notifications /org/freedesktop/Notifications org.freedesktop.Notifications.GetServerInformation | ${grep} -q "mako"; then
      ${makoctl} reload
    fi
  fi
'';

but i am not sure if this is the best solution compared to e.g. checking that an instance of mako is running by using pgrep.

PS: As far as i understand, this is a similar root cause to #3172

Maintainer CC

@onny

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.6.63, NixOS, 25.05 (Warbler), 25.05.20241207.22c3f2c`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.24.10`
 - channels(root): `""`
 - nixpkgs: `/nix/store/avxvalb7xf8x4avmrbcvn1vr5yy46kxs-source`