lib/modules: disallow setting config, options in specialArgs of evalModules (#388834)

lib/modules.nix

@@ -5,6 +5,7 @@ let
     addErrorContext
     all
     any
+    assertMsg
     attrByPath
     attrNames
     catAttrs
@@ -101,6 +102,8 @@ let
                 , # This would be remove in the future, Prefer _module.check option instead.
                   check ? true
                 }:
+    assert assertMsg (!specialArgs?config) "Do not set config in the specialArgs argument to evalModules.";
+    assert assertMsg (!specialArgs?options) "Do not set options in the specialArgs argument to evalModules.";
     let
       withWarnings = x:
         warnIf (evalModulesArgs?args) "The args argument to evalModules is deprecated. Please set config._module.args instead."

lib/tests/modules.sh

@@ -137,6 +137,9 @@ checkConfigOutput '^true$' config.result ./module-argument-default.nix
 # gvariant
 checkConfigOutput '^true$' config.assertion ./gvariant.nix
 
+# specialArgs checks for evalModules
+checkConfigError 'Do not set config in the specialArgs argument to evalModules\.' config.fail.config ./specialArgs-config.nix
+checkConfigError 'Do not set options in the specialArgs argument to evalModules\.' config.fail.config ./specialArgs-options.nix
 checkConfigOutput '"ok"' config.result ./specialArgs-lib.nix
 
 # https://github.com/NixOS/nixpkgs/pull/131205

lib/tests/modules/specialArgs-config.nix

@@ -0,0 +1,18 @@
+{ lib, ... }:
+{
+  config = {
+    _module.freeformType = lib.types.anything;
+
+    fail = lib.evalModules {
+      specialArgs = {
+        config = { };
+      };
+      modules = [
+        {
+          options.a = lib.mkEnableOption "a";
+          config.a = true;
+        }
+      ];
+    };
+  };
+}

lib/tests/modules/specialArgs-options.nix

@@ -0,0 +1,18 @@
+{ lib, ... }:
+{
+  config = {
+    _module.freeformType = lib.types.anything;
+
+    fail = lib.evalModules {
+      specialArgs = {
+        options = { };
+      };
+      modules = [
+        {
+          options.a = lib.mkEnableOption "a";
+          config.a = true;
+        }
+      ];
+    };
+  };
+}