chore(overlays): trivial builder wrappers

nixos/base/nixpkgs.nix

@@ -1,7 +1,32 @@
-{gensokyo-zone, ...}: let
+{
+  config,
+  system,
+  gensokyo-zone,
+  lib,
+  ...
+}: let
+  inherit (gensokyo-zone.lib) mkAlmostForce;
+  inherit (lib.options) mkOption;
+  inherit (lib.modules) mkIf mkDefault;
+  inherit (lib.attrsets) optionalAttrs;
   inherit (gensokyo-zone.self) overlays;
+  cfg = config.nixpkgs;
+  hostPlatform = lib.systems.elaborate {
+    inherit (system) system;
+  };
 in {
-  nixpkgs = {
+  options.nixpkgs = with lib.types; {
+    usePkgs = mkOption {
+      type = enum ["legacyPackages.pkgs" "import" "nixos"];
+      description = "gensokyo-zone#legacyPackages.pkgs";
+      default =
+        if cfg.buildPlatform == cfg.hostPlatform && cfg.hostPlatform == hostPlatform && gensokyo-zone.self ? legacyPackages.${cfg.hostPlatform.system}.pkgs
+        then "legacyPackages.pkgs"
+        else "import";
+    };
+  };
+  config.nixpkgs = {
+    hostPlatform = mkDefault hostPlatform;
     overlays = [
       gensokyo-zone.inputs.arcexprs.overlays.default
       overlays.default
@@ -13,4 +38,18 @@ in {
       ];
     };
   };
+  config._module.args.pkgs = let
+    pkgsArgs = {
+      inherit (cfg) config overlays;
+      localSystem = cfg.buildPlatform;
+    };
+    pkgsCrossArgs = optionalAttrs (cfg.buildPlatform != cfg.hostPlatform) {
+      crossSystem = cfg.hostPlatform;
+    };
+    pkgs = {
+      "legacyPackages.pkgs" = gensokyo-zone.self.legacyPackages.${cfg.hostPlatform.system}.pkgs;
+      import = import gensokyo-zone.inputs.nixpkgs (pkgsArgs // pkgsCrossArgs);
+    };
+  in
+    mkIf (cfg.usePkgs != "nixos") (mkAlmostForce pkgs.${cfg.usePkgs}.__withSubBuilders);
 }

outputs.nix

@@ -14,18 +14,22 @@
       devShells = import ./devShells.nix {inherit system inputs;};
       packages = import ./packages {inherit system inputs;};
       legacyPackages = {
-        pkgs = import inputs.nixpkgs {
-          inherit system;
-          overlays = [
-            inputs.self.overlays.default
-            inputs.self.overlays.deploy-rs
-            inputs.self.overlays.systemd2mqtt
-            inputs.self.overlays.arc
-          ];
-          config = {
-            allowUnfree = true;
+        pkgs = let
+          pkgs = import inputs.nixpkgs {
+            inherit system;
+            overlays = [
+              inputs.self.overlays.default
+              inputs.self.overlays.deploy-rs
+              inputs.self.overlays.systemd2mqtt
+              inputs.self.overlays.arc
+            ];
+            config = {
+              allowUnfree = true;
+            };
           };
-        };
+          # see overlays/builders.nix
+        in
+          pkgs.__withSubBuilders;
         patchedNixpkgs = pkgs.applyPatches {
           name = "nixpkgs";
           src = inputs.nixpkgs;

overlays/builders.nix

@@ -0,0 +1,76 @@
+final: prev: let
+  inherit (final.lib.attrsets) mapAttrs' nameValuePair;
+  subBuilders = {
+    applyPatches = args:
+      prev.applyPatches ({
+          allowSubstitutes = true;
+        }
+        // args);
+    writeTextFile = args:
+      prev.writeTextFile ({
+          allowSubstitutes = true;
+        }
+        // args);
+    writeText = name: text: final.writeTextFile' {inherit name text;};
+    writeShellScript = name: text:
+      final.writeTextFile' {
+        inherit name;
+        executable = true;
+        text = ''
+          #!${final.runtimeShell}
+          ${text}
+        '';
+        checkPhase = ''
+          ${final.stdenv.shellDryRun} "$target"
+        '';
+      };
+    writeShellScriptBin = name: text:
+      final.writeTextFile' {
+        inherit name;
+        destination = "/bin/${name}";
+        executable = true;
+        text = ''
+          #!${final.runtimeShell}
+          ${text}
+        '';
+        checkPhase = ''
+          ${final.stdenv.shellDryRun} "$target"
+        '';
+      };
+    symlinkJoin = args:
+      prev.symlinkJoin ({
+          allowSubstitutes = true;
+        }
+        // args);
+    linkFarm = name: entries:
+      (prev.linkFarm name entries).overrideAttrs (_: {
+        allowSubstitutes = true;
+      });
+    runCommandLocal = name: env:
+      final.runCommandWith {
+        stdenv = final.stdenvNoCC;
+        runLocal = true;
+        inherit name;
+        derivationArgs =
+          {
+            allowSubstitutes = true;
+          }
+          // env;
+      };
+    # TODO: writeScript, writeScriptBin, runCommandWith...
+  };
+  subBuilders' = mapAttrs' (name: nameValuePair "${name}'") subBuilders;
+in {
+  inherit
+    (subBuilders')
+    applyPatches'
+    writeTextFile'
+    writeText'
+    writeShellScript'
+    writeShellScriptBin'
+    symlinkJoin'
+    linkFarm'
+    runCommandLocal'
+    ;
+  __withSubBuilders = final // subBuilders;
+}

overlays/default.nix

@@ -3,6 +3,7 @@
 in rec {
   default = nixlib.composeManyExtensions [
     barcodebuddy
+    builders
     krb5
     minecraft
     nfs
@@ -17,6 +18,7 @@ in rec {
   nginx = import ./nginx.nix;
   samba = import ./samba.nix;
   openwebrx = import ./openwebrxplus.nix;
+  builders = import ./builders.nix;
   deploy-rs = inputs.deploy-rs.overlays.default or inputs.deploy-rs.overlay;
   systemd2mqtt = inputs.systemd2mqtt.overlays.default;
   arc = inputs.arcexprs.overlays.default;