refactor(nix): self-guard hardware modules

Author: edmundmiller

default.nix

@@ -18,8 +18,6 @@ with lib.my;
       let
         modulesPath = toString ./modules;
         allModulePaths = mapModulesRec' modulesPath id;
-        # Filter out NixOS-only directories on Darwin
-        nixosOnlyDirs = [ "hardware" ];
         # NixOS-only subdirectories within desktop (allow desktop/term for ghostty)
         nixosOnlyDesktopDirs = [
           "desktop/browsers"
@@ -48,7 +46,7 @@ with lib.my;
           "desktop/gnome.nix" # GNOME desktop environment
           "desktop/kde.nix" # KDE desktop environment
           "desktop/bspwm.nix" # BSPWM window manager
-          # NixOS-only hardware/shell modules
+          # NixOS-only shell modules
           "nushell.nix"
           "yubikey.nix"
           # NixOS-only services
@@ -81,7 +79,7 @@ with lib.my;
             lib.hasInfix "/modules/${dir}/" pathStr
             # Files inside directory
             || lib.hasSuffix "/modules/${dir}" pathStr # Directory itself
-          ) (nixosOnlyDirs ++ nixosOnlyDesktopDirs)
+          ) nixosOnlyDesktopDirs
           || lib.any (
             file:
             lib.hasSuffix file pathStr

lib/platform.nix

@@ -9,13 +9,53 @@ let
   isDarwin = hasSuffix "darwin" system;
   isLinux = hasSuffix "linux" system;
   isNixOS = isLinux; # For clarity when we specifically mean NixOS
+
+  mkUnsupportedPlatformConfig =
+    {
+      enabled,
+      moduleName,
+      supportedPlatform,
+      unsupported,
+      config,
+    }:
+    mkMerge (
+      [
+        {
+          assertions = [
+            {
+              assertion = !(enabled && unsupported);
+              message = "${moduleName} is only supported on ${supportedPlatform}.";
+            }
+          ];
+        }
+      ]
+      ++ optional (!unsupported) (mkIf enabled config)
+    );
+
+  mkNixOSOnlyConfig =
+    isDarwin: moduleName: enabled: config:
+    mkUnsupportedPlatformConfig {
+      inherit enabled moduleName config;
+      supportedPlatform = "NixOS";
+      unsupported = isDarwin;
+    };
+
+  mkDarwinOnlyConfig =
+    isDarwin: moduleName: enabled: config:
+    mkUnsupportedPlatformConfig {
+      inherit enabled moduleName config;
+      supportedPlatform = "Darwin";
+      unsupported = !isDarwin;
+    };
 in
 {
   inherit
     isDarwin
     isLinux
     isNixOS
     system
+    mkNixOSOnlyConfig
+    mkDarwinOnlyConfig
     ;
 
   # Helper to get the correct home base directory

modules/hardware/audio.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -15,7 +16,7 @@ in
     easyeffects.enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable (mkMerge [
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.audio" cfg.enable (mkMerge [
     {
       services.pipewire = {
         enable = true;

modules/hardware/bluetooth.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -16,7 +17,7 @@ in
     audio.enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable (mkMerge [
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.bluetooth" cfg.enable (mkMerge [
     { hardware.bluetooth.enable = true; }
 
     (mkIf cfg.audio.enable {

modules/hardware/ergodox.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -19,7 +20,7 @@ in
     };
   };
 
-  config = mkIf cfg.enable {
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.ergodox" cfg.enable {
     user.packages = with pkgs; [
       teensy-loader-cli
       # QMK build environment for local firmware compilation

modules/hardware/fs.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -17,7 +18,7 @@ in
     # TODO automount.enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable (mkMerge [
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.fs" cfg.enable (mkMerge [
     {
       programs.udevil.enable = true;
 

modules/hardware/nvidia.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -14,7 +15,7 @@ in
     enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable {
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.nvidia" cfg.enable {
     hardware.graphics.enable = true;
 
     services.xserver.videoDrivers = [ "nvidia" ];

modules/hardware/printing.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -14,7 +15,7 @@ in
     enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable {
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.printing" cfg.enable {
     services.printing.enable = true;
     services.printing.drivers = [ pkgs.brlaser ];
     # Network discovery

modules/hardware/sensors.nix

@@ -2,6 +2,7 @@
   config,
   lib,
   pkgs,
+  isDarwin,
   ...
 }:
 with lib;
@@ -14,5 +15,7 @@ in
     enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable { user.packages = [ pkgs.lm_sensors ]; };
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.sensors" cfg.enable {
+    user.packages = [ pkgs.lm_sensors ];
+  };
 }

modules/hardware/wacom.nix

@@ -1,6 +1,7 @@
 {
   config,
   lib,
+  isDarwin,
   ...
 }:
 with lib;
@@ -13,7 +14,7 @@ in
     enable = mkBoolOpt false;
   };
 
-  config = mkIf cfg.enable {
+  config = mkNixOSOnlyConfig isDarwin "modules.hardware.wacom" cfg.enable {
     # For my intuos4 pro. Doesn't work for cintiqs.
     services.xserver.wacom.enable = true;
     # TODO Move this to udev