zellij: Add extraConfig

This allows working around [#4659](https://github.com/nix-community/home-manager/issues/4659)

While fixing `toKDL` might be fun, I just don't think it's a good use of
anyone's time.

---

This is still untested.

modules/programs/zellij.nix

@@ -34,12 +34,44 @@ in {
       '';
       description = ''
         Configuration written to
-        {file}`$XDG_CONFIG_HOME/zellij/config.yaml`.
+        {file}`$XDG_CONFIG_HOME/zellij/config.kdl`.
 
         See <https://zellij.dev/documentation> for the full
         list of options.
       '';
     };
+    extraConfig = lib.mkOption {
+      description = ''
+        Extra configuration lines to add to `$XDG_CONFIG_HOME/zellij/config.kdl`.
+
+        This does not support zellij.yaml and it's mostly a workaround for https://github.com/nix-community/home-manager/issues/4659.
+      '';
+      type = lib.types.lines;
+      default = "";
+      example = ''
+        keybinds {
+            // keybinds are divided into modes
+            normal {
+                // bind instructions can include one or more keys (both keys will be bound separately)
+                // bind keys can include one or more actions (all actions will be performed with no sequential guarantees)
+                bind "Ctrl g" { SwitchToMode "locked"; }
+                bind "Ctrl p" { SwitchToMode "pane"; }
+                bind "Alt n" { NewPane; }
+                bind "Alt h" "Alt Left" { MoveFocusOrTab "Left"; }
+            }
+            pane {
+                bind "h" "Left" { MoveFocus "Left"; }
+                bind "l" "Right" { MoveFocus "Right"; }
+                bind "j" "Down" { MoveFocus "Down"; }
+                bind "k" "Up" { MoveFocus "Up"; }
+                bind "p" { SwitchFocus; }
+            }
+            locked {
+                bind "Ctrl g" { SwitchToMode "normal"; }
+            }
+        }
+      '';
+    };
 
     enableBashIntegration = mkEnableOption "Bash integration" // {
       default = false;
@@ -61,12 +93,17 @@ in {
     # https://github.com/zellij-org/zellij/releases/tag/v0.32.0
     xdg.configFile."zellij/config.yaml" = mkIf
       (cfg.settings != { } && (versionOlder cfg.package.version "0.32.0")) {
-        source = yamlFormat.generate "zellij.yaml" cfg.settings;
+        source = (yamlFormat.generate "zellij.yaml" cfg.settings);
       };
 
     xdg.configFile."zellij/config.kdl" = mkIf
       (cfg.settings != { } && (versionAtLeast cfg.package.version "0.32.0")) {
-        text = lib.hm.generators.toKDL { } cfg.settings;
+        text = (lib.hm.generators.toKDL { } cfg.settings)
+          + lib.optionalString (cfg.extraConfig != "") (''
+
+            // extraConfig
+
+          '' + cfg.extraConfig);
       };
 
     programs.bash.initExtra = mkIf cfg.enableBashIntegration (mkOrder 200 ''

tests/modules/programs/zellij/config.nix

@@ -0,0 +1,33 @@
+{ lib, ... }:
+
+{
+  programs = {
+    zellij = {
+      enable = true;
+
+      settings = { default_layout = "welcome"; };
+      extraConfig = ''
+        This_could_have_been_json {
+        }
+      '';
+    };
+  };
+
+  test.stubs = { zellij = { }; };
+
+  nmt.script = ''
+    assertFileExists home-files/.config/zellij/config.kdl
+
+    assertFileContains \
+      home-files/.config/zellij/config.kdl \
+      'default_layout "welcome"'
+
+    assertFileContains \
+      home-files/.config/zellij/config.kdl \
+      '// extraConfig'
+
+    assertFileContains \
+      home-files/.config/zellij/config.kdl \
+      'This_could_have_been_json'
+  '';
+}

tests/modules/programs/zellij/default.nix

@@ -1 +1,4 @@
-{ zellij-enable-shells = ./enable-shells.nix; }
+{
+  zellij-config = ./config.nix;
+  zellij-enable-shells = ./enable-shells.nix;
+}