Add test that shows that the aliases are able to override options.

lib/tests/modules.sh

@@ -151,6 +151,9 @@ checkConfigOutput "1 2 3 4 5 6 7 8 9 10" config.result ./loaOf-with-many-list-me
 
 # Check mkAliasOptionModuleWithPriority.
 checkConfigOutput "true" config.enable ./alias-with-priority.nix
+checkConfigOutput "true" config.enableAlias ./alias-with-priority.nix
+checkConfigOutput "false" config.enable ./alias-with-priority-can-override.nix
+checkConfigOutput "false" config.enableAlias ./alias-with-priority-can-override.nix
 
 cat <<EOF
 ====== module tests ======

lib/tests/modules/alias-with-priority-can-override.nix

@@ -0,0 +1,52 @@
+# This is a test to show that mkAliasOptionModule sets the priority correctly
+# for aliased options.
+
+{ config, lib, ... }:
+
+with lib;
+
+{
+  options = {
+    # A simple boolean option that can be enabled or disabled.
+    enable = lib.mkOption {
+      type = types.nullOr types.bool;
+      default = null;
+      example = true;
+      description = ''
+        Some descriptive text
+      '';
+    };
+
+    # mkAliasOptionModule sets warnings, so this has to be defined.
+    warnings = mkOption {
+      internal = true;
+      default = [];
+      type = types.listOf types.str;
+      example = [ "The `foo' service is deprecated and will go away soon!" ];
+      description = ''
+        This option allows modules to show warnings to users during
+        the evaluation of the system configuration.
+      '';
+    };
+  };
+
+  imports = [
+    # Create an alias for the "enable" option.
+    (mkAliasOptionModuleWithPriority [ "enableAlias" ] [ "enable" ])
+
+    # Disable the aliased option, but with a default (low) priority so it
+    # should be able to be overridden by the next import.
+    ( { config, lib, ... }:
+      {
+        enableAlias = lib.mkForce false;
+      }
+    )
+
+    # Enable the normal (non-aliased) option.
+    ( { config, lib, ... }:
+      {
+        enable = true;
+      }
+    )
+  ];
+}