Merge pull request #48 from hercules-ci/moduleWithSystem

Add `moduleWithSystem` flake module parameter

modules/moduleWithSystem.nix

@@ -0,0 +1,32 @@
+{ config, lib, withSystem, ... }:
+{
+  config = {
+    _module.args = {
+      moduleWithSystem =
+        module:
+
+        { config, ... }:
+        let
+          system =
+            config._module.args.system or
+              config._module.args.pkgs.stdenv.hostPlatform.system or
+                (throw "moduleWithSystem: Could not determine the configuration's system parameter for this module system application.");
+
+          allArgs = withSystem system (args: args);
+
+          lazyArgsPerParameter = f: builtins.mapAttrs
+            (k: v: allArgs.${k} or (throw "moduleWithSystem: module argument `${k}` does not exist."))
+            (builtins.functionArgs f);
+
+          # Use reflection to make the call lazy in the argument.
+          # Restricts args to the ones declared.
+          callLazily = f: a: f (lazyArgsPerParameter f);
+        in
+        {
+          imports = [
+            (callLazily module allArgs)
+          ];
+        };
+    };
+  };
+}