zellij: Allow using extraConfig without settings

Fixes https://github.com/nix-community/home-manager/issues/8015

modules/programs/zellij.nix

@@ -274,12 +274,15 @@ in
         {
 
           "zellij/config.yaml" =
-            mkIf (cfg.settings != { } && (lib.versionOlder cfg.package.version "0.32.0"))
+            mkIf ((lib.versionOlder cfg.package.version "0.32.0") && cfg.settings != { })
               {
                 source = yamlFormat.generate "zellij.yaml" cfg.settings;
               };
           "zellij/config.kdl" =
-            mkIf (cfg.settings != { } && (lib.versionAtLeast cfg.package.version "0.32.0"))
+            mkIf
+              (
+                (lib.versionAtLeast cfg.package.version "0.32.0") && (cfg.settings != { } || cfg.extraConfig != "")
+              )
               {
                 text =
                   (lib.hm.generators.toKDL { } cfg.settings)

tests/modules/programs/zellij/config-extra_config.nix

@@ -0,0 +1,29 @@
+{
+  programs = {
+    zellij = {
+      enable = true;
+
+      # No `settings`
+      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 \
+      '// extraConfig'
+
+    assertFileContains \
+      home-files/.config/zellij/config.kdl \
+      'This_could_have_been_json'
+  '';
+}

tests/modules/programs/zellij/config-mixed.nix

@@ -1,5 +1,3 @@
-{ lib, ... }:
-
 {
   programs = {
     zellij = {

tests/modules/programs/zellij/config-settings.nix

@@ -0,0 +1,24 @@
+{
+  programs = {
+    zellij = {
+      enable = true;
+
+      settings = {
+        default_layout = "welcome";
+      };
+      # No extraConfig
+    };
+  };
+
+  test.stubs = {
+    zellij = { };
+  };
+
+  nmt.script = ''
+    assertFileExists home-files/.config/zellij/config.kdl
+
+    assertFileContains \
+      home-files/.config/zellij/config.kdl \
+      'default_layout "welcome"'
+  '';
+}

tests/modules/programs/zellij/default.nix

@@ -1,5 +1,7 @@
 {
-  zellij-config = ./config.nix;
+  zellij-config-mixed = ./config-mixed.nix;
+  zellij-config-settings = ./config-settings.nix;
+  zellij-config-extra_config = ./config-extra_config.nix;
   zellij-enable-shells = ./enable-shells.nix;
   zellij-layout = ./layout.nix;
   zellij-theme = ./theme.nix;