nilla: migrate devshells

.envrc

@@ -1 +1,2 @@
 use flake
+watch_file nilla.nix

flake.nix

@@ -1,6 +1,9 @@
 {
   outputs =
     inputs@{ flake-parts, ... }:
+    let
+      nilla = import ./nilla.nix { inherit inputs; };
+    in
     flake-parts.lib.mkFlake { inherit inputs; } {
       systems = [
         "x86_64-linux"
@@ -24,17 +27,11 @@
           inputs',
           self',
           pkgs,
+          system,
           ...
         }:
         {
-          devShells.default = pkgs.mkShellNoCC {
+          devShells = builtins.mapAttrs (_: shell: shell.result.${system}) nilla.shells;
-            packages = [
-              inputs'.agenix.packages.agenix
-              self'.packages.attic-client
-              # TODO: Contribute darwin support to nh
-              pkgs.nh
-            ];
-          };
 
           packages = {
             # Re-export it for convenience and for caching

nilla.nix

@@ -2,7 +2,7 @@
   inputs ? import ./inputs.nix,
 }:
 (import inputs.nilla).create (
-  { lib }:
+  { config, lib }:
   {
     config.inputs = builtins.mapAttrs (_: src: {
       inherit src;
@@ -20,17 +20,87 @@
       build =
         pkg:
         lib.attrs.generate pkg.systems (
-          system: inputs.nixpkgs.legacyPackages.${system}.callPackage pkg.package pkg.settings.args
+          system:
+          inputs.nixpkgs.legacyPackages.${system}.callPackage pkg.package (
+            {
+              self' = builtins.mapAttrs (_: pkg: pkg.result.${system}) config.packages;
+            }
+            // pkg.settings.args
+          )
         );
     };
 
+    config.builders.custom-load = {
+      settings.type = lib.types.submodule {
+        options.args = lib.options.create {
+          type = lib.types.null;
+          default.value = null;
+        };
+      };
+      settings.default = { };
+      build = pkg: lib.attrs.generate pkg.systems (system: pkg.package { inherit system; });
+    };
+
+    config.packages =
+      let
+        systems = [
+          "x86_64-linux"
+          "aarch64-linux"
+          "aarch64-darwin"
+        ];
+        mkPackage = package: {
+          builder = "nixpkgs-flake";
+          inherit systems package;
+        };
+        mkPackageFlakeOutput =
+          {
+            input,
+            output ? input,
+          }:
+          {
+            inherit systems;
+            builder = "custom-load";
+            package = { system }: inputs.${input}.packages.${system}.${output};
+          };
+      in
+      {
+        attic-client = mkPackageFlakeOutput {
+          input = "attic";
+          output = "attic-client";
+        };
+        attic-server = mkPackageFlakeOutput {
+          input = "attic";
+          output = "attic-server";
+        };
+        agenix = mkPackageFlakeOutput { input = "agenix"; };
+        base-packages = mkPackage (
+          { symlinkJoin }:
+          symlinkJoin {
+            name = "settei-base";
+            paths = [ ];
+          }
+        );
+      };
+
     config.shells.default = {
-      systems = [ "x86_64-linux" ];
+      systems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "aarch64-darwin"
+      ];
       builder = "nixpkgs-flake";
       shell =
-        { mkShell, hello }:
+        {
-        mkShell {
+          mkShellNoCC,
-          packages = [ hello ];
+          nh,
+          self',
+        }:
+        mkShellNoCC {
+          packages = [
+            self'.agenix
+            self'.attic-client
+            nh
+          ];
         };
     };
   }