sway: fix error with null package and swaybar

When setting `...sway.package = null`, the default bar configuration
would throw an error trying to use the bar from the null package.

Logic is added to use the bar from `pkgs.sway` instead of `cfg.package`
if it is null.

Fixes #1714

modules/services/window-managers/i3-sway/lib/options.nix

@@ -120,7 +120,11 @@ let
 
       command = mkOption {
         type = types.str;
-        default = "${cfg.package}/bin/${moduleName}bar";
+        default = let
+          # If the user uses the "system" Sway (i.e. cfg.package == null) then the bar has
+          # to come from a different package
+          pkg = if isSway && isNull cfg.package then pkgs.sway else cfg.package;
+        in "${pkg}/bin/${moduleName}bar";
         defaultText = "i3bar";
         description = "Command that will be used to start a bar.";
         example = if isI3 then

tests/modules/services/window-managers/sway/default.nix

@@ -3,4 +3,5 @@
   sway-post-2003 = ./sway-post-2003.nix;
   sway-followmouse = ./sway-followmouse.nix;
   sway-followmouse-legacy = ./sway-followmouse-legacy.nix;
+  sway-null-package = ./sway-null-package.nix;
 }

tests/modules/services/window-managers/sway/sway-null-package.conf

@@ -0,0 +1,117 @@
+font pango:monospace 8
+floating_modifier Mod1
+default_border pixel 2
+default_floating_border pixel 2
+hide_edge_borders none
+focus_wrapping no
+focus_follows_mouse yes
+focus_on_window_activation smart
+mouse_warping output
+workspace_layout default
+workspace_auto_back_and_forth no
+
+client.focused #4c7899 #285577 #ffffff #2e9ef4 #285577
+client.focused_inactive #333333 #5f676a #ffffff #484e50 #5f676a
+client.unfocused #333333 #222222 #888888 #292d2e #222222
+client.urgent #2f343a #900000 #ffffff #900000 #900000
+client.placeholder #000000 #0c0c0c #ffffff #000000 #0c0c0c
+client.background #ffffff
+
+bindsym Mod1+1 workspace number 1
+bindsym Mod1+2 workspace number 2
+bindsym Mod1+3 workspace number 3
+bindsym Mod1+4 workspace number 4
+bindsym Mod1+5 workspace number 5
+bindsym Mod1+6 workspace number 6
+bindsym Mod1+7 workspace number 7
+bindsym Mod1+8 workspace number 8
+bindsym Mod1+9 workspace number 9
+bindsym Mod1+Down focus down
+bindsym Mod1+Left focus left
+bindsym Mod1+Return exec @rxvt-unicode-unwrapped@/bin/urxvt
+bindsym Mod1+Right focus right
+bindsym Mod1+Shift+1 move container to workspace number 1
+bindsym Mod1+Shift+2 move container to workspace number 2
+bindsym Mod1+Shift+3 move container to workspace number 3
+bindsym Mod1+Shift+4 move container to workspace number 4
+bindsym Mod1+Shift+5 move container to workspace number 5
+bindsym Mod1+Shift+6 move container to workspace number 6
+bindsym Mod1+Shift+7 move container to workspace number 7
+bindsym Mod1+Shift+8 move container to workspace number 8
+bindsym Mod1+Shift+9 move container to workspace number 9
+bindsym Mod1+Shift+Down move down
+bindsym Mod1+Shift+Left move left
+bindsym Mod1+Shift+Right move right
+bindsym Mod1+Shift+Up move up
+bindsym Mod1+Shift+c reload
+bindsym Mod1+Shift+e exec swaynag -t warning -m 'You pressed the exit shortcut. Do you really want to exit sway? This will end your Wayland session.' -b 'Yes, exit sway' 'swaymsg exit'
+bindsym Mod1+Shift+h move left
+bindsym Mod1+Shift+j move down
+bindsym Mod1+Shift+k move up
+bindsym Mod1+Shift+l move right
+bindsym Mod1+Shift+minus move scratchpad
+bindsym Mod1+Shift+q kill
+bindsym Mod1+Shift+space floating toggle
+bindsym Mod1+Up focus up
+bindsym Mod1+a focus parent
+bindsym Mod1+b splith
+bindsym Mod1+d exec @dmenu@/bin/dmenu_run
+bindsym Mod1+e layout toggle split
+bindsym Mod1+f fullscreen toggle
+bindsym Mod1+h focus left
+bindsym Mod1+j focus down
+bindsym Mod1+k focus up
+bindsym Mod1+l focus right
+bindsym Mod1+minus scratchpad show
+bindsym Mod1+r mode resize
+bindsym Mod1+s layout stacking
+bindsym Mod1+space focus mode_toggle
+bindsym Mod1+v splitv
+bindsym Mod1+w layout tabbed
+
+
+
+mode "resize" {
+bindsym Down resize grow height 10 px
+bindsym Escape mode default
+bindsym Left resize shrink width 10 px
+bindsym Return mode default
+bindsym Right resize grow width 10 px
+bindsym Up resize shrink height 10 px
+bindsym h resize shrink width 10 px
+bindsym j resize grow height 10 px
+bindsym k resize shrink height 10 px
+bindsym l resize grow width 10 px
+}
+
+
+bar {
+  
+  font pango:monospace 8
+  mode dock
+  hidden_state hide
+  position bottom
+  status_command @i3status@/bin/i3status
+  swaybar_command @sway@/bin/swaybar
+  workspace_buttons yes
+  strip_workspace_numbers no
+  tray_output primary
+  colors {
+    background #000000
+    statusline #ffffff
+    separator #666666
+    focused_workspace #4c7899 #285577 #ffffff
+    active_workspace #333333 #5f676a #ffffff
+    inactive_workspace #333333 #222222 #888888
+    urgent_workspace #2f343a #900000 #ffffff
+    binding_mode #2f343a #900000 #ffffff
+  }
+  
+}
+
+
+
+
+
+
+exec "systemctl --user import-environment; systemctl --user start sway-session.target"

tests/modules/services/window-managers/sway/sway-null-package.nix

@@ -0,0 +1,45 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  dummy-package = pkgs.runCommandLocal "dummy-package" { } "mkdir $out";
+
+in {
+  config = {
+    # Enables the default bar configuration
+    home.stateVersion = "20.09";
+
+    wayland.windowManager.sway = {
+      enable = true;
+      package = null;
+      config.menu = "${pkgs.dmenu}/bin/dmenu_run";
+    };
+
+    nixpkgs.overlays = [
+      (self: super: {
+        dmenu = dummy-package // { outPath = "@dmenu@"; };
+        rxvt-unicode-unwrapped = dummy-package // {
+          outPath = "@rxvt-unicode-unwrapped@";
+        };
+        i3status = dummy-package // { outPath = "@i3status@"; };
+        sway = dummy-package // { outPath = "@sway@"; };
+        xwayland = dummy-package // { outPath = "@xwayland@"; };
+      })
+    ];
+
+    assertions = [{
+      assertion =
+        !elem config.wayland.windowManager.sway.config.bars [ [ { } ] [ ] ];
+      message =
+        "The default Sway bars configuration should be set for this test (sway-null-package) to work.";
+    }];
+
+    nmt.script = ''
+      assertFileExists home-files/.config/sway/config
+      assertFileContent home-files/.config/sway/config \
+        ${./sway-null-package.conf}
+    '';
+  };
+}