modules: add support for module replacement with disabledModules

This is based on a prototype Nicolas B. Pierron worked on during a
discussion we had at FOSDEM.

A new version with a workaround for problems of the reverted original.
Discussion: https://github.com/NixOS/nixpkgs/commit/3f2566689

lib/tests/modules.sh

@@ -99,6 +99,14 @@ checkConfigOutput 'true' "$@" ./define-enable.nix ./define-loaOfSub-if-foo-enabl
 checkConfigOutput 'true' "$@" ./define-enable.nix ./define-loaOfSub-foo-if-enable.nix
 checkConfigOutput 'true' "$@" ./define-enable.nix ./define-loaOfSub-foo-enable-if.nix
 
+# Check disabledModules with config definitions and option declarations.
+set -- config.enable ./define-enable.nix ./declare-enable.nix
+checkConfigOutput "true" "$@"
+checkConfigOutput "false" "$@" ./disable-define-enable.nix
+checkConfigError "The option .*enable.* defined in .* does not exist" "$@" ./disable-declare-enable.nix
+checkConfigError "attribute .*enable.* in selection path .*config.enable.* not found" "$@" ./disable-define-enable.nix ./disable-declare-enable.nix
+checkConfigError "attribute .*enable.* in selection path .*config.enable.* not found" "$@" ./disable-enable-modules.nix
+
 # Check _module.args.
 set -- config.enable ./declare-enable.nix ./define-enable-with-custom-arg.nix
 checkConfigError 'while evaluating the module argument .*custom.* in .*define-enable-with-custom-arg.nix.*:' "$@"

lib/tests/modules/default.nix

@@ -3,5 +3,6 @@
 {
   inherit (lib.evalModules {
     inherit modules;
+    specialArgs.modulesPath = ./.;
   }) config options;
 }

lib/tests/modules/disable-declare-enable.nix

@@ -0,0 +1,5 @@
+{ lib, ... }:
+
+{
+  disabledModules = [ ./declare-enable.nix ];
+}

lib/tests/modules/disable-define-enable.nix

@@ -0,0 +1,5 @@
+{ lib, ... }:
+
+{
+  disabledModules = [ ./define-enable.nix ];
+}

lib/tests/modules/disable-enable-modules.nix

@@ -0,0 +1,5 @@
+{ lib, ... }:
+
+{
+  disabledModules = [ "define-enable.nix" "declare-enable.nix" ];
+}