xsession: add option `importedVariables`

This option lists the environment variables to be imported into the
systemd user session.

Also add a basic test of the xsession module.

modules/misc/qt.nix

@@ -65,8 +65,7 @@ in
       then [ pkgs.qgnomeplatform ]
       else [ pkgs.libsForQt5.qtstyleplugins ];
 
-    xsession.profileExtra =
-      "systemctl --user import-environment QT_QPA_PLATFORMTHEME";
+    xsession.importedVariables = [ "QT_QPA_PLATFORMTHEME" ];
 
     # Enable GTK+ style for Qt4 in either case.
     # It doesn’t support the platform theme packages.

modules/services/taffybar.nix

@@ -42,5 +42,7 @@ in
         WantedBy = [ "graphical-session.target" ];
       };
     };
+
+    xsession.importedVariables = [ "GDK_PIXBUF_MODULE_FILE" ];
   };
 }

modules/xsession.nix

@@ -62,10 +62,31 @@ in
         default = "";
         description = "Extra shell commands to run during initialization.";
       };
+
+      importedVariables = mkOption {
+        type = types.listOf (types.strMatching "[a-zA-Z_][a-zA-Z0-9_]*");
+        example = [ "GDK_PIXBUF_ICON_LOADER" ];
+        visible = false;
+        description = ''
+          Environment variables to import into the user systemd
+          session. The will be available for use by graphical
+          services.
+        '';
+      };
     };
   };
 
   config = mkIf cfg.enable {
+    xsession.importedVariables = [
+      "DBUS_SESSION_BUS_ADDRESS"
+      "DISPLAY"
+      "SSH_AUTH_SOCK"
+      "XAUTHORITY"
+      "XDG_DATA_DIRS"
+      "XDG_RUNTIME_DIR"
+      "XDG_SESSION_ID"
+    ];
+
     systemd.user = {
       services = mkIf (config.home.keyboard != null) {
         setxkbmap =  {
@@ -118,13 +139,10 @@ in
         # script starts up graphical-session.target.
         systemctl --user stop graphical-session.target graphical-session-pre.target
 
-        systemctl --user import-environment DBUS_SESSION_BUS_ADDRESS
-        systemctl --user import-environment DISPLAY
-        systemctl --user import-environment SSH_AUTH_SOCK
-        systemctl --user import-environment XAUTHORITY
-        systemctl --user import-environment XDG_DATA_DIRS
-        systemctl --user import-environment XDG_RUNTIME_DIR
-        systemctl --user import-environment XDG_SESSION_ID
+        ${optionalString (cfg.importedVariables != []) (
+          "systemctl --user import-environment "
+            + toString (unique cfg.importedVariables)
+        )}
 
         ${cfg.profileExtra}
 

tests/default.nix

@@ -33,6 +33,7 @@ import nmt {
       i3-keybindings = ./modules/services/window-managers/i3-keybindings.nix;
     }
     // import ./modules/misc/pam
+    // import ./modules/misc/xsession
     // import ./modules/systemd
   )
   // import ./modules/home-environment

tests/modules/misc/xsession/basic-xprofile-expected.txt

@@ -0,0 +1,16 @@
+. "/test-home/.nix-profile/etc/profile.d/hm-session-vars.sh"
+
+if [[ -e "$HOME/.profile" ]]; then
+  . "$HOME/.profile"
+fi
+
+# If there are any running services from a previous session.
+# Need to run this in xprofile because the NixOS xsession
+# script starts up graphical-session.target.
+systemctl --user stop graphical-session.target graphical-session-pre.target
+
+systemctl --user import-environment DBUS_SESSION_BUS_ADDRESS DISPLAY SSH_AUTH_SOCK XAUTHORITY XDG_DATA_DIRS XDG_RUNTIME_DIR XDG_SESSION_ID EXTRA_IMPORTED_VARIABLE
+
+profile extra commands
+
+export HM_XPROFILE_SOURCED=1

tests/modules/misc/xsession/basic-xsession-expected.txt

@@ -0,0 +1,18 @@
+if [[ ! -v HM_XPROFILE_SOURCED ]]; then
+  . ~/.xprofile
+fi
+unset HM_XPROFILE_SOURCED
+
+systemctl --user start hm-graphical-session.target
+
+init extra commands
+
+window manager command
+
+systemctl --user stop graphical-session.target
+systemctl --user stop graphical-session-pre.target
+
+# Wait until the units actually stop.
+while [[ -n "$(systemctl --user --no-legend --state=deactivating list-units)" ]]; do
+  sleep 0.5
+done

tests/modules/misc/xsession/basic.nix

@@ -0,0 +1,30 @@
+{ config, lib, ... }:
+
+with lib;
+
+{
+  config = {
+    home.homeDirectory = "/test-home";
+
+    xsession = {
+      enable = true;
+      windowManager.command = "window manager command";
+      importedVariables = [ "EXTRA_IMPORTED_VARIABLE" ];
+      initExtra = "init extra commands";
+      profileExtra = "profile extra commands";
+    };
+
+    nmt.script = ''
+      assertFileExists home-files/.xprofile
+      assertFileContent \
+        home-files/.xprofile \
+        ${./basic-xprofile-expected.txt}
+
+      assertFileExists home-files/.xsession
+      assertFileContent \
+        home-files/.xsession \
+        ${./basic-xsession-expected.txt}
+
+    '';
+  };
+}

tests/modules/misc/xsession/default.nix

@@ -0,0 +1,3 @@
+{
+  xsession-basic = ./basic.nix;
+}