Refactor unfree aspect to use a module

modules/aspects/provides/inputs.nix

@@ -1,6 +1,12 @@
 { den, withSystem, ... }:
+let
+  inherit (den.lib)
+    parametric
+    take
+    ;
+in
 {
-  den.provides.inputs' = den.lib.parametric.exactly {
+  den.provides.inputs' = parametric.exactly {
     description = ''
       Provides the `flake-parts` `inputs'` (the flake's `inputs` with system pre-selected)
       as a top-level module argument.
@@ -30,12 +36,12 @@
       (
         { OS, host }:
         let
-          unused = den.lib.take.unused OS;
+          unused = take.unused OS;
         in
         withSystem host.system (
           { inputs', ... }:
-          {
-            ${host.class}._module.args.inputs' = unused inputs';
+          unused {
+            ${host.class}._module.args.inputs' = inputs';
           }
         )
       )
@@ -47,27 +53,27 @@
           host,
         }:
         let
-          unused = den.lib.take.unused [
+          unused = take.unused [
             OS
             HM
           ];
         in
         withSystem host.system (
           { inputs', ... }:
-          {
-            ${user.class}._module.args.inputs' = unused inputs';
+          unused {
+            ${user.class}._module.args.inputs' = inputs';
           }
         )
       )
       (
         { HM, home }:
         let
-          unused = den.lib.take.unused HM;
+          unused = take.unused HM;
         in
         withSystem home.system (
           { inputs', ... }:
-          {
-            ${home.class}._module.args.inputs' = unused inputs';
+          unused {
+            ${home.class}._module.args.inputs' = inputs';
           }
         )
       )

modules/aspects/provides/unfree/unfree-predicate-builder.nix

@@ -0,0 +1,91 @@
+{ den, lib, ... }:
+let
+  inherit (den.lib)
+    parametric
+    take
+    ;
+
+  description = ''
+    This is a private aspect always included in den.default.
+
+    It adds a module option that gathers all packages defined
+    in den._.unfree usages and declares a 
+    nixpkgs.config.allowUnfreePredicate for each class.
+
+  '';
+
+  unfreeComposableModule.options.unfree = {
+    packages = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      default = [ ];
+    };
+  };
+
+  nixosAspect =
+    { config, ... }:
+    {
+      nixpkgs.config.allowUnfreePredicate = (pkg: builtins.elem (lib.getName pkg) config.unfree.packages);
+    };
+
+  homeManagerAspect =
+    { config, osConfig, ... }:
+    {
+      nixpkgs = lib.mkIf (!osConfig.home-manager.useGlobalPkgs) {
+        config.allowUnfreePredicate = (pkg: builtins.elem (lib.getName pkg) config.unfree.packages);
+      };
+    };
+
+  aspect = parametric.exactly {
+    inherit description;
+    includes = [
+      (
+        { OS, host }:
+        let
+          unused = take.unused OS;
+        in
+        {
+          ${host.class}.imports = unused [
+            unfreeComposableModule
+            nixosAspect
+          ];
+        }
+      )
+      (
+        {
+          OS,
+          HM,
+          user,
+          host,
+        }:
+        let
+          unused = take.unused [
+            OS
+            HM
+            host
+          ];
+        in
+        {
+          ${user.class}.imports = unused [
+            unfreeComposableModule
+            homeManagerAspect
+          ];
+        }
+      )
+      (
+        { HM, home }:
+        let
+          unused = take.unused HM;
+        in
+        {
+          ${home.class}.imports = unused [
+            unfreeComposableModule
+            nixosAspect
+          ];
+        }
+      )
+    ];
+  };
+in
+{
+  den.default.includes = [ aspect ];
+}

modules/aspects/provides/unfree.nix → modules/aspects/provides/unfree/unfree.nix

@@ -1,4 +1,4 @@
-{ lib, den, ... }:
+{ den, ... }:
 {
   den.provides.unfree.description = ''
     A class generic aspect that enables unfree packages by name.
@@ -16,6 +16,6 @@
     _self: allowed-names:
     { class, aspect-chain }:
     den.lib.take.unused aspect-chain {
-      ${class}.nixpkgs.config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) allowed-names;
+      ${class}.unfree.packages = allowed-names;
     };
 }

templates/examples/modules/_example/ci/unfree.nix

@@ -1,6 +1,25 @@
 { den, ... }:
+
+let
+  codeAspect = {
+    includes = [ (den._.unfree [ "vscode" ]) ];
+    homeManager.programs.vscode.enable = true;
+  };
+  discordAspect = {
+    includes = [
+      (den._.unfree [ "discord" ])
+    ];
+    homeManager =
+      { pkgs, ... }:
+      {
+        home.packages = [ pkgs.discord ];
+      };
+  };
+in
 {
-  # cam uses unfree vscode.
-  den.aspects.cam.homeManager.programs.vscode.enable = true;
-  den.aspects.cam.includes = [ (den._.unfree [ "vscode" ]) ];
+  # cam uses unfree vscode and discord loaded from different aspects.
+  den.aspects.cam.includes = [
+    codeAspect
+    discordAspect
+  ];
 }