WIP: flake: home-manager: export NixOS homes

WIP: this does not take into account the `profiles` which *also* setup
home-manager modules...

And here is what the last few commits were building up to.

This is neat, but won't be useful *very* often.

flake/default.nix

@@ -13,6 +13,7 @@ flake-parts.lib.mkFlake { inherit inputs; } {
     ./checks.nix
     ./dev-shells.nix
     ./home-manager.nix
+    ./hosts.nix
     ./lib.nix
     ./nixos.nix
     ./overlays.nix

flake/home-manager.nix

@@ -1,5 +1,7 @@
-{ self, inputs, lib, ... }:
+{ self, config, inputs, lib, ... }:
 let
+  inherit (config) hosts;
+
   defaultModules = [
     # Include generic settings
     "${self}/modules/home"
@@ -16,7 +18,7 @@ let
     }
   ];
 
-  mkHome = name: system: inputs.home-manager.lib.homeManagerConfiguration {
+  mkHomeCommon = mainModule: system: inputs.home-manager.lib.homeManagerConfiguration {
     # Work-around for home-manager
     # * not letting me set `lib` as an extraSpecialArgs
     # * not respecting `nixpkgs.overlays` [1]
@@ -29,9 +31,7 @@ let
       ];
     };
 
-    modules = defaultModules ++ [
-      "${self}/hosts/homes/${name}"
-    ];
+    modules = defaultModules ++ [ mainModule ];
 
     extraSpecialArgs = {
       # Inject inputs to use them in global registry
@@ -39,24 +39,37 @@ let
     };
   };
 
-  homes = {
+  mkHome = name: mkHomeCommon "${self}/hosts/homes/${name}";
+
+  mkNixosHome = name: mkHomeCommon "${self}/hosts/nixos/${name}/home.nix";
+in
+{
+  hosts.homes = {
     "ambroisie@bazin" = "x86_64-linux";
     "ambroisie@mousqueton" = "x86_64-linux";
   };
-in
-{
+
   perSystem = { system, ... }: {
     # Work-around for https://github.com/nix-community/home-manager/issues/3075
     legacyPackages = {
       homeConfigurations =
         let
-          filteredHomes = lib.filterAttrs (_: v: v == system) homes;
+          filteredHomes = lib.filterAttrs (_: v: v == system) hosts.homes;
           allHomes = filteredHomes // {
             # Default configuration
             ambroisie = system;
           };
+          homeManagerHomes = lib.mapAttrs mkHome allHomes;
+
+          filteredNixosHosts = lib.filterAttrs (_: v: v == system) hosts.nixos;
+          nixosHomes' = lib.mapAttrs mkNixosHome filteredNixosHosts;
+          nixosHomes = lib.mapAttrs' (host: lib.nameValuePair "ambroisie@${host}") nixosHomes';
         in
-        lib.mapAttrs mkHome allHomes;
+        lib.foldl' lib.mergeAttrs { }
+          [
+            homeManagerHomes
+            nixosHomes
+          ];
     };
   };
 }

flake/hosts.nix

@@ -0,0 +1,21 @@
+# Define `hosts.{darwin,home,nixos}` options for consumption in other modules
+{ lib, ... }:
+let
+  mkHostsOption = description: lib.mkOption {
+    inherit description;
+    type = with lib.types; attrsOf str;
+    default = { };
+    example = { name = "x86_64-linux"; };
+  };
+in
+{
+  options = {
+    hosts = {
+      darwin = mkHostsOption "Darwin hosts";
+
+      homes = mkHostsOption "Home Manager hosts";
+
+      nixos = mkHostsOption "NixOS hosts";
+    };
+  };
+}

flake/nixos.nix

@@ -1,4 +1,4 @@
-{ self, inputs, lib, ... }:
+{ self, config, inputs, lib, ... }:
 let
   defaultModules = [
     {
@@ -28,8 +28,12 @@ let
   };
 in
 {
-  flake.nixosConfigurations = lib.mapAttrs buildHost {
-    aramis = "x86_64-linux";
-    porthos = "x86_64-linux";
+  config = {
+    hosts.nixos = {
+      aramis = "x86_64-linux";
+      porthos = "x86_64-linux";
+    };
+
+    flake.nixosConfigurations = lib.mapAttrs buildHost config.hosts.nixos;
   };
 }