From 1f8f4cc2f8e621994db88b7df74c83edafada753 Mon Sep 17 00:00:00 2001
From: Ananya Timalsina <84459091+ananyatimalsina@users.noreply.github.com>
Date: Sun, 1 Mar 2026 15:40:25 +0100
Subject: [PATCH] feat(nix): add build-time configuration validation

Uses `pkgs.runCommand` in the home-manager module to parse and validate
the generated config file prior to deployment, preventing broken setups.
---
 nix/hm-modules.nix | 102 +++++++++++++++++++++++++--------------------
 1 file changed, 56 insertions(+), 46 deletions(-)

diff --git a/nix/hm-modules.nix b/nix/hm-modules.nix
index 4d48ddf6..f00d9c68 100644
--- a/nix/hm-modules.nix
+++ b/nix/hm-modules.nix
@@ -211,53 +211,63 @@ in
     };
   };
 
-  config = lib.mkIf cfg.enable {
-    # Backwards compatibility warning for old string-based config
-    warnings = lib.optional (builtins.isString cfg.settings) ''
-      wayland.windowManager.mango.settings: Using a string for settings is deprecated.
-      Please migrate to the new structured attribute set format.
-      See the module documentation for examples, or use the 'extraConfig' option for raw config strings.
-      The old string format will be removed in a future release.
-    '';
+  config = lib.mkIf cfg.enable (
+    let
+      finalConfigText =
+        # Support old string-based config during transition period
+        (
+          if builtins.isString cfg.settings then
+            cfg.settings
+          else
+            lib.optionalString (cfg.settings != { }) (
+              selflib.toMango {
+                topCommandsPrefixes = cfg.topPrefixes;
+                bottomCommandsPrefixes = cfg.bottomPrefixes;
+              } cfg.settings
+            )
+        )
+        + lib.optionalString (cfg.extraConfig != "") cfg.extraConfig
+        + lib.optionalString (cfg.autostart_sh != "") "\nexec-once=~/.config/mango/autostart.sh\n";
 
-    home.packages = [ cfg.package ];
-    xdg.configFile = {
-      "mango/config.conf" =
-        lib.mkIf (cfg.settings != { } || cfg.extraConfig != "" || cfg.autostart_sh != "")
-          {
-            text =
-              # Support old string-based config during transition period
-              (
-                if builtins.isString cfg.settings then
-                  cfg.settings
-                else
-                  lib.optionalString (cfg.settings != { }) (
-                    selflib.toMango {
-                      topCommandsPrefixes = cfg.topPrefixes;
-                      bottomCommandsPrefixes = cfg.bottomPrefixes;
-                    } cfg.settings
-                  )
-              )
-              + lib.optionalString (cfg.extraConfig != "") cfg.extraConfig
-              + lib.optionalString (cfg.autostart_sh != "") "\nexec-once=~/.config/mango/autostart.sh\n";
-          };
-      "mango/autostart.sh" = lib.mkIf (cfg.autostart_sh != "") {
-        source = autostart_sh;
-        executable = true;
+      validatedConfig = pkgs.runCommand "mango-config.conf" { } ''
+        cp ${pkgs.writeText "mango-config.conf" finalConfigText} "$out"
+        ${cfg.package}/bin/mango -c "$out" -p || exit 1
+      '';
+    in
+    {
+      # Backwards compatibility warning for old string-based config
+      warnings = lib.optional (builtins.isString cfg.settings) ''
+        wayland.windowManager.mango.settings: Using a string for settings is deprecated.
+        Please migrate to the new structured attribute set format.
+        See the module documentation for examples, or use the 'extraConfig' option for raw config strings.
+        The old string format will be removed in a future release.
+      '';
+
+      home.packages = [ cfg.package ];
+      xdg.configFile = {
+        "mango/config.conf" =
+          lib.mkIf (cfg.settings != { } || cfg.extraConfig != "" || cfg.autostart_sh != "")
+            {
+              source = validatedConfig;
+            };
+        "mango/autostart.sh" = lib.mkIf (cfg.autostart_sh != "") {
+          source = autostart_sh;
+          executable = true;
+        };
       };
-    };
-    systemd.user.targets.mango-session = lib.mkIf cfg.systemd.enable {
-      Unit = {
-        Description = "mango compositor session";
-        Documentation = [ "man:systemd.special(7)" ];
-        BindsTo = [ "graphical-session.target" ];
-        Wants = [
-          "graphical-session-pre.target"
-        ]
-        ++ lib.optional cfg.systemd.xdgAutostart "xdg-desktop-autostart.target";
-        After = [ "graphical-session-pre.target" ];
-        Before = lib.optional cfg.systemd.xdgAutostart "xdg-desktop-autostart.target";
+      systemd.user.targets.mango-session = lib.mkIf cfg.systemd.enable {
+        Unit = {
+          Description = "mango compositor session";
+          Documentation = [ "man:systemd.special(7)" ];
+          BindsTo = [ "graphical-session.target" ];
+          Wants = [
+            "graphical-session-pre.target"
+          ]
+          ++ lib.optional cfg.systemd.xdgAutostart "xdg-desktop-autostart.target";
+          After = [ "graphical-session-pre.target" ];
+          Before = lib.optional cfg.systemd.xdgAutostart "xdg-desktop-autostart.target";
+        };
       };
-    };
-  };
+    }
+  );
 }