evalArgs: general api improvements

drop default channel, it is confusing and complicates api
don't take nixos input, using channels is better
manually pass names for outputs to improve documentation

lib/mkFlake/evalArgs.nix

@@ -1,11 +1,12 @@
 { lib }:
 
-{ nixos, args }:
+{ args }:
 let
   argOpts = with lib; { config, ... }:
     let
       inherit (lib) os;
 
+      cfg = config;
       inherit (config) self;
 
       maybeImport = obj:
@@ -33,23 +34,19 @@ let
       # To simplify apply keys and improve type checking
       pathTo = elemType: with types; coercedTo path maybeImport elemType;
 
-      # Accepts single item or a list
+      pathToListOf = elemType: with types; pathTo (listOf elemType);
-      # apply keys end up with a list
-      # This should not be used if expecting a nested list
-      # all lists will get flattened by this
-      coercedListOf = elemType:
-        let coerceToList = x: flatten (singleton x); in
-        with types; coercedTo elemType coerceToList (listOf elemType);
 
-      pathToListOf = x: pathTo (coercedListOf x);
+      coercedListOf = elemType: with types;
+        coercedTo elemType (x: flatten (singleton x)) (listOf elemType);
 
       /* Submodules needed for API containers */
 
-      channelsModule = {
+      channelsModule = { name, ... }: {
         options = with types; {
           input = mkOption {
             type = flakeType;
-            default = nixos;
+            default = cfg.inputs.${name};
+            defaultText = escape [ "<" ">" ] "inputs.<name>";
             description = ''
               nixpkgs flake input to use for this channel
             '';
@@ -57,22 +54,15 @@ let
           overlays = mkOption {
             type = pathToListOf overlayType;
             default = [ ];
-            description = ''
+            description = escape [ "<" ">" ] ''
               overlays to apply to this channel
               these will get exported under the 'overlays' flake output as <channel>/<name>
             '';
           };
-          externalOverlays = mkOption {
-            type = pathToListOf overlayType;
-            default = [ ];
-            description = ''
-              overlays to apply to the channel that don't get exported to the flake output
-              useful to include overlays from inputs
-            '';
-          };
           config = mkOption {
             type = pathTo attrs;
             default = { };
+            apply = lib.recursiveUpdate cfg.channelsConfig;
             description = ''
               nixpkgs config for this channel
             '';
@@ -82,21 +72,21 @@ let
 
       hostModule = {
         options = with types; {
+          # anything null in hosts gets filtered out by mkFlake
           system = mkOption {
-            type = systemType;
+            type = nullOr systemType;
-            default = "x86_64-linux";
+            default = null;
             description = ''
               system for this host
             '';
           };
           channelName = mkOption {
-            type = types.enum (builtins.attrValues config.channels);
+            type = nullOr (types.enum (builtins.attrNames config.channels));
-            default = "nixpkgs";
+            default = null;
             description = ''
               Channel this host should follow
             '';
           };
-
         };
       };
 
@@ -105,7 +95,7 @@ let
       externalModulesModule = {
         options = {
           externalModules = mkOption {
-            type = pathToListOf moduleType;
+            type = with types; listOf moduleType;
             default = [ ];
             description = ''
               The configuration for this host
@@ -117,7 +107,7 @@ let
       modulesModule = {
         options = {
           modules = mkOption {
-            type = pathToListOf moduleType;
+            type = with types; coercedListOf moduleType;
             default = [ ];
             description = ''
               modules to include
@@ -126,13 +116,34 @@ let
         };
       };
 
+      exportModulesModule = name: {
+        options = {
+          modules = mkOption {
+            type = with types; pathToListOf
+              # check if the path evaluates to a proper module
+              # but this must be a path for the export to work
+              (addCheck path (x: moduleType.check (import x)));
+            default = [ ];
+            description = ''
+              modules to include in all hosts and export to ${name}Modules output
+            '';
+          };
+        };
+      };
+
+
+
       # Home-manager's configs get exported automatically from nixos.hosts
       # So there is no need for a host options in the home namespace
       # This is only needed for nixos
-      includeHostsModule = { name, ... }: {
+      includeHostsModule = name: {
         options = with types; {
           hostDefaults = mkOption {
-            type = submodule [ hostModule externalModulesModule modulesModule ];
+            type = submodule [
+              hostModule
+              externalModulesModule
+              (exportModulesModule name)
+            ];
             default = { };
             description = ''
               Defaults for all hosts.
@@ -152,15 +163,11 @@ let
       };
 
       # profiles and suites - which are profile collections
-      profilesModule = { name, ... }: {
+      profilesModule = { config, ... }: {
         options = with types; {
           profiles = mkOption {
-            type = coercedListOf path;
+            type = listOf path;
             default = [ ];
-            apply = list:
-              # Merge a list of profiles to one set
-              let profileList = map (x: os.mkProfileAttrs (toString x)) list; in
-              foldl (a: b: a // b) { } profileList;
             description = "path to profiles folder that can be collected into suites";
           };
           suites = mkOption {
@@ -185,6 +192,13 @@ let
           type = flakeType;
           description = "The flake to create the devos outputs for";
         };
+        inputs = mkOption {
+          type = attrsOf flakeType;
+          description = ''
+            inputs for this flake
+            used to set channel defaults and create registry
+          '';
+        };
         supportedSystems = mkOption {
           type = listOf str;
           default = lib.defaultSystems;
@@ -192,31 +206,33 @@ let
             The systems supported by this flake
           '';
         };
-        channels =
+        channelsConfig = mkOption {
-          let
+          type = pathTo attrs;
-            default = {
+          default = { };
-              nixpkgs = {
+          description = ''
-                input = nixos;
+            nixpkgs config for all channels
-              };
+          '';
-            };
+        };
-          in
+        channels = mkOption {
-          mkOption {
+          type = attrsOf (submodule channelsModule);
-            type = attrsOf (submodule channelsModule);
+          default = { };
-            inherit default;
+          description = ''
-            apply = x: default // x;
+            nixpkgs channels to create
-            description = ''
+          '';
-              nixpkgs channels to create
+        };
-            '';
+        nixos = mkOption {
-          };
+          type = submodule [ (includeHostsModule "nixos") profilesModule ];
-        os = mkOption {
-          type = submodule [ includeHostsModule profilesModule ];
           default = { };
           description = ''
             hosts, modules, suites, and profiles for nixos
           '';
         };
         home = mkOption {
-          type = submodule [ profilesModule modulesModule ];
+          type = submodule [
+            profilesModule
+            (exportModulesModule "home")
+            externalModulesModule
+          ];
           default = { };
           description = ''
             hosts, modules, suites, and profiles for home-manager