lib/src/modules/default.nix

@@ -237,27 +237,8 @@ lib: {
                     namespaces ++ [ namespace ];
               in
               builtins.foldl' filter [ ] normalized;
-
-            createNamespacedModule =
-              { namespace, module, ... }:
-              if namespace == null then
-                module
-              else
-                {
-                  __key__ = "${__key__}:include-${namespace}";
-                  options.${namespace} = lib.options.create {
-                    description = "options and configuration included from ${namespace}";
-                    default.value = { };
-                    type = lib.types.submodules.of {
-                      modules = [ module ];
-                      description = "include ${namespace}";
-                    };
-                  };
-                };
-
-            namespacedModules = builtins.map createNamespacedModule normalized;
           in
-          builtins.seq throwOnConflict namespacedModules;
+          builtins.seq throwOnConflict normalized;
       in
       if lib.modules.validate.keys module then
         {
@@ -587,19 +568,36 @@ lib: {
         collect =
           let
             load =
-              args: file: key: module:
+              args: file: key: module':
               let
+                namespace = module'.namespace or null;
+                module = module'.module or module';
+
                 moduleFromValue = lib.modules.normalize file key (lib.modules.resolve key module args);
                 moduleFromPath = lib.modules.normalize (builtins.toString module) (builtins.toString module) (
                   lib.modules.resolve (builtins.toString module) (import module) args
                 );
               in
-              if builtins.isAttrs module || builtins.isFunction module then
-                moduleFromValue
-              else if builtins.isString module || builtins.isPath module then
-                moduleFromPath
+              if namespace == null then
+                if builtins.isAttrs module || builtins.isFunction module then
+                  moduleFromValue
+                else if builtins.isString module || builtins.isPath module then
+                  moduleFromPath
+                else
+                  builtins.throw "The provided module must be either an attribute set, function, or path but got ${builtins.typeOf module}"
+              # We don't resolve the module yet if we're under a namespace
               else
-                builtins.throw "The provided module must be either an attribute set, function, or path but got ${builtins.typeOf module}";
+                lib.modules.normalize file key {
+                  __key__ = "${key}:include-${namespace}";
+                  options.${namespace} = lib.options.create {
+                    description = "options and configuration included from ${namespace}";
+                    default.value = { };
+                    type = lib.types.submodules.of {
+                      modules = [ module ];
+                      description = "include ${namespace}";
+                    };
+                  };
+                };
 
             normalize =
               parentFile: parentKey: modules: args:

lib/src/modules/default.test.nix

@@ -305,30 +305,25 @@ in
       "handles a mixed list" =
         let
           expected = [
-            null
-            { a = null; }
+            {
+              module = { };
+              namespace = null;
+            }
+            {
+              module = { };
+              namespace = "a";
+            }
           ];
           actual =
-            # Because includes leverage submodules, we can't match the actual
-            # included namespaced submodule under "a". So we just assert the
-            # namespace was gotten right and do not evaluate the included value.
-            builtins.map
-              (
-                include:
-                if builtins.isAttrs include then
-                  builtins.mapAttrs (_: _: null) include.options or include
-                else
-                  include
-              )
-              (lib.modules.normalize "/aux/example.nix" "example" {
-                includes = [
-                  null
-                  {
-                    module = null;
-                    namespace = "a";
-                  }
-                ];
-              }).includes;
+            (lib.modules.normalize "/aux/example.nix" "example" {
+              includes = [
+                { }
+                {
+                  module = { };
+                  namespace = "a";
+                }
+              ];
+            }).includes;
         in
         expected == actual;
 
@@ -337,11 +332,11 @@ in
           normalized = lib.modules.normalize "/aux/example.nix" "example" {
             includes = [
               {
-                module = null;
+                module = { };
                 namespace = "a";
               }
               {
-                module = null;
+                module = { };
                 namespace = "a";
               }
             ];
@@ -353,8 +348,8 @@ in
         let
           normalized = lib.modules.normalize "/aux/example.nix" "example" {
             includes = [
-              null
-              null
+              { }
+              { }
             ];
           };
         in
@@ -363,14 +358,20 @@ in
       "handles multiple without namespace" =
         let
           expected = [
-            null
-            null
+            {
+              namespace = null;
+              module = { };
+            }
+            {
+              namespace = null;
+              module = { };
+            }
           ];
           actual =
             (lib.modules.normalize "/aux/example.nix" "example" {
               includes = [
-                null
-                null
+                { }
+                { }
               ];
             }).includes;
         in