[WIP] nix.nix: split, align and reuse macros from NixOS

docs/default.nix

@@ -1,6 +1,6 @@
 # Copyright (c) 2019-2023, see AUTHORS. Licensed under MIT License, see LICENSE.
 
-{ pkgs, home-manager, nmdSrc }:
+{ pkgs, nixpkgs, home-manager, nmdSrc }:
 
 let
   nmd = import nmdSrc { inherit pkgs; };
@@ -14,7 +14,7 @@ let
   };
 
   modules = import ../modules/module-list.nix {
-    inherit pkgs;
+    inherit pkgs nixpkgs;
     home-manager-path = home-manager.outPath;
     isFlake = true;
   };

flake.nix

@@ -25,7 +25,7 @@
     };
   };
 
-  outputs = { self, nixpkgs, nixpkgs-for-bootstrap, home-manager, nix-formatter-pack, nmd }:
+  outputs = { self, nixpkgs, nixpkgs-for-bootstrap, home-manager, nix-formatter-pack, nmd }@inputs:
     let
       forEachSystem = nixpkgs.lib.genAttrs [ "aarch64-linux" "x86_64-linux" ];
 
@@ -80,6 +80,7 @@
         { modules ? [ ]
         , extraSpecialArgs ? { }
         , pkgs ? pkgs'
+        , nixpkgs ? inputs.nixpkgs
         , home-manager-path ? home-manager.outPath
           # deprecated:
         , config ? null
@@ -103,7 +104,7 @@
               See the 22.11 release notes for more.
             ''
             (import ./modules {
-              inherit extraSpecialArgs home-manager-path pkgs;
+              inherit extraSpecialArgs home-manager-path nixpkgs pkgs;
               config.imports = modules;
               isFlake = true;
             });
@@ -118,7 +119,7 @@
           };
 
           docs = import ./docs {
-            inherit home-manager;
+            inherit nixpkgs home-manager;
             pkgs = nixpkgs.legacyPackages.${system};
             nmdSrc = nmd;
           };

modules/default.nix

@@ -3,6 +3,7 @@
 { config ? null
 , extraSpecialArgs ? { }
 , pkgs ? import <nixpkgs> { }
+, nixpkgs ? <nixpkgs>
 , home-manager-path ? <home-manager>
 , isFlake ? false
 }:
@@ -21,7 +22,7 @@ let
 
   rawModule = evalModules {
     modules = [ configModule ] ++ nodModules;
-    specialArgs = extraSpecialArgs;
+    specialArgs = { inherit nixpkgs; } // extraSpecialArgs;
   };
 
   failedAssertions = map (x: x.message) (filter (x: !x.assertion) rawModule.config.assertions);

modules/environment/nix-channel.nix

@@ -0,0 +1,44 @@
+# Copyright (c) 2019-2022, see AUTHORS. Licensed under MIT License, see LICENSE.
+
+# Based on
+# https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/config/nix-channel.nix
+# (Copyright (c) 2003-2022 Eelco Dolstra and the Nixpkgs/NixOS contributors,
+# licensed under MIT License as well)
+
+{ config, lib, pkgs, nixpkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.nix;
+  renameNixOpt = old: new:
+    (mkRenamedOptionModule [ "nix" old ] [ "nix" new ]);
+in
+
+{
+  ###### interface
+
+  options = {
+
+    nix = {
+      nixPath = mkOption {
+        type = types.listOf types.str;
+        default = [ ];
+        description = ''
+          The default Nix expression search path, used by the Nix
+          evaluator to look up paths enclosed in angle brackets
+          (e.g. <literal>&lt;nixpkgs&gt;</literal>).
+        '';
+      };
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = {
+    environment.sessionVariables.NIX_PATH = concatStringsSep ":" cfg.nixPath;
+  };
+
+}

modules/environment/nix-flakes.nix

@@ -0,0 +1,21 @@
+# Copyright (c) 2019-2022, see AUTHORS. Licensed under MIT License, see LICENSE.
+
+# Based on
+# https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/config/nix-flakes.nix
+# (Copyright (c) 2003-2022 Eelco Dolstra and the Nixpkgs/NixOS contributors,
+# licensed under MIT License as well)
+
+{ config, lib, pkgs, nixpkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.nix;
+in
+
+{
+  imports = [
+    # Use options and config from upstream nix-flakes.nix
+    "${nixpkgs}/nixos/modules/config/nix-flakes.nix"
+  ];
+}

modules/environment/nix.nix

@@ -1,171 +1,81 @@
 # Copyright (c) 2019-2022, see AUTHORS. Licensed under MIT License, see LICENSE.
 
 # Based on
-# https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/misc/nix-daemon.nix
+# https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/system/nix-daemon.nix
+# and
+# https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/config/nix.nix
 # (Copyright (c) 2003-2022 Eelco Dolstra and the Nixpkgs/NixOS contributors,
 # licensed under MIT License as well)
 
-{ config, lib, pkgs, ... }:
+{ config, lib, pkgs, nixpkgs, ... }:
 
 with lib;
 
 let
   cfg = config.nix;
   renameNixOpt = old: new:
-    (mkRenamedOptionModule [ "nix" old ] [ "nix" new ]);
+    mkRenamedOptionModuleWith {
+      sinceRelease = 2205;
+      from = [ "nix" old ];
+      to = [ "nix" "settings" new ];
+    };
 in
 
 {
-  # Backward-compatibility with the NixOS options.
   imports = [
-    (renameNixOpt "binaryCaches" "substituters")
-    (renameNixOpt "binaryCachePublicKeys" "trustedPublicKeys")
-    (renameNixOpt "extraConfig" "extraOptions")
+    # Use options and config from upstream nix.nix
+    "${nixpkgs}/nixos/modules/config/nix.nix"
+    # Backward-compatibility with pre-`settings` options.
+    (renameNixOpt "substituters" "substituters")
+    (renameNixOpt "trustedPublicKeys" "trusted-public-keys")
   ];
 
   ###### interface
 
   options = {
 
     nix = {
-      package = mkOption {
-        type = types.package;
-        default = pkgs.nix;
-        defaultText = literalExpression "pkgs.nix";
-        description = ''
-          This option specifies the Nix package instance to use throughout the system.
-        '';
-      };
 
-      nixPath = mkOption {
-        type = types.listOf types.str;
-        default = [ ];
-        description = ''
-          The default Nix expression search path, used by the Nix
-          evaluator to look up paths enclosed in angle brackets
-          (e.g. <literal>&lt;nixpkgs&gt;</literal>).
-        '';
-      };
+      ## From nix-daemon.nix
 
-      registry = mkOption {
-        type = types.attrsOf (types.submodule (
-          let
-            referenceAttrs = with types; attrsOf (oneOf [
-              str
-              int
-              bool
-              package
-            ]);
-          in
-          { config, name, ... }:
-          {
-            options = {
-              from = mkOption {
-                type = referenceAttrs;
-                example = { type = "indirect"; id = "nixpkgs"; };
-                description = "The flake reference to be rewritten.";
-              };
-              to = mkOption {
-                type = referenceAttrs;
-                example = { type = "github"; owner = "my-org"; repo = "my-nixpkgs"; };
-                description = "The flake reference <option>from</option> is rewritten to.";
-              };
-              flake = mkOption {
-                type = types.nullOr types.attrs;
-                default = null;
-                example = literalExpression "nixpkgs";
-                description = ''
-                  The flake input <option>from</option> is rewritten to.
-                '';
-              };
-              exact = mkOption {
-                type = types.bool;
-                default = true;
-                description = ''
-                  Whether the <option>from</option> reference needs to match exactly. If set,
-                  a <option>from</option> reference like <literal>nixpkgs</literal> does not
-                  match with a reference like <literal>nixpkgs/nixos-20.03</literal>.
-                '';
-              };
-            };
-            config = {
-              from = mkDefault { type = "indirect"; id = name; };
-              to = mkIf (config.flake != null) (mkDefault
-                {
-                  type = "path";
-                  path = config.flake.outPath;
-                } // filterAttrs
-                (n: _: n == "lastModified" || n == "rev" || n == "revCount" || n == "narHash")
-                config.flake);
-            };
-          }
-        ));
-        default = { };
-        description = "A system-wide flake registry.";
-      };
-
-      substituters = mkOption {
-        type = types.listOf types.str;
-        default = [ ];
+      enable = mkOption {
+        type = types.bool;
+        default = true;
         description = ''
-          A list of URLs of substituters.  The official NixOS and Nix-on-Droid
-          substituters are added by default.
+          Whether to enable Nix.
+          Disabling Nix is not supported in NixOnDroid. This option is here to
+          make it compatible to the upstream NixOS modules.
         '';
       };
 
-      trustedPublicKeys = mkOption {
-        type = types.listOf types.str;
-        default = [ ];
+      package = mkOption {
+        type = types.package;
+        default = pkgs.nix;
+        defaultText = literalExpression "pkgs.nix";
         description = ''
-          A list of public keys.  When paths are copied from another Nix store (such as a
-          binary cache), they must be signed with one of these keys.  The official NixOS
-          and Nix-on-Droid public keys are added by default.
+          This option specifies the Nix package instance to use throughout the system.
         '';
       };
 
-      extraOptions = mkOption {
-        type = types.lines;
-        default = "";
-        description = "Extra config to be appended to <filename>/etc/nix/nix.conf</filename>.";
-      };
     };
 
   };
 
 
   ###### implementation
 
-  config = mkMerge [
-    {
-      environment.etc = {
-        "nix/nix.conf".text = ''
-          sandbox = false
-          substituters = ${concatStringsSep " " cfg.substituters}
-          trusted-public-keys = ${concatStringsSep " " cfg.trustedPublicKeys}
-          ${cfg.extraOptions}
-        '';
-
-        "nix/registry.json".text = builtins.toJSON {
-          version = 2;
-          flakes = mapAttrsToList (_n: v: { inherit (v) from to exact; }) cfg.registry;
-        };
-      };
-
-      nix = {
-        substituters = [
-          "https://cache.nixos.org"
-          "https://nix-on-droid.cachix.org"
-        ];
-        trustedPublicKeys = [
-          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
-          "nix-on-droid.cachix.org-1:56snoMJTXmDRC1Ei24CmKoUqvHJ9XCp+nidK7qkMQrU="
-        ];
-      };
-    }
-
-    (mkIf (cfg.nixPath != [ ]) {
-      environment.sessionVariables.NIX_PATH = concatStringsSep ":" cfg.nixPath;
-    })
-  ];
+  config = {
+    nix = {
+      enable = true;
+      settings.substituters = [
+        "https://cache.nixos.org"
+        "https://nix-on-droid.cachix.org"
+      ];
+      settings.trusted-public-keys = [
+        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+        "nix-on-droid.cachix.org-1:56snoMJTXmDRC1Ei24CmKoUqvHJ9XCp+nidK7qkMQrU="
+      ];
+    };
+  };
 
 }