modules: Add mkSinkUndeclaredOptions.

lib/options.nix

@@ -31,6 +31,23 @@ rec {
     type = lib.types.bool;
   };
 
+  # This option accept anything, but it does not produce any result.  This
+  # is useful for sharing a module across different module sets without
+  # having to implement similar features as long as the value of the options
+  # are not expected.
+  mkSinkUndeclaredOptions = attrs: mkOption ({
+    internal = true;
+    visible = false;
+    default = false;
+    description = "Sink for option definitions.";
+    type = mkOptionType {
+      name = "sink";
+      check = x: true;
+      merge = loc: defs: false;
+    };
+    apply = x: throw "Option value is not readable because the option is not declared.";
+  } // attrs);
+
   mergeDefaultOption = loc: defs:
     let list = getValues defs; in
     if length list == 1 then head list