flake: use flake-parts

flake.lock

@@ -247,6 +247,10 @@
     "root": {
       "inputs": {
         "clan-core": "clan-core",
+        "flake-parts": [
+          "clan-core",
+          "flake-parts"
+        ],
         "nixos-mailserver": "nixos-mailserver",
         "nixpkgs": [
           "clan-core",

flake.nix

@@ -7,13 +7,16 @@
   inputs.nixos-mailserver.url = "gitlab:simple-nixos-mailserver/nixos-mailserver/nixos-26.05";
   inputs.nixos-mailserver.inputs.nixpkgs.follows = "nixpkgs";
 
+  inputs.flake-parts.follows = "clan-core/flake-parts";
+
   outputs =
-    {
+    inputs@{
       self,
       clan-core,
       nixpkgs,
+      flake-parts,
       ...
-    }@inputs:
+    }:
     let
       # Usage see: https://docs.clan.lol
       clan = clan-core.lib.clan {
@@ -36,38 +39,31 @@
           "age-plugin-fido2-hmac"
         ];
       };
-
+    in
+    flake-parts.lib.mkFlake { inherit inputs; } {
       systems = [
         "x86_64-linux"
         "aarch64-linux"
         "aarch64-darwin"
         "x86_64-darwin"
       ];
-      forAllSystems = nixpkgs.lib.genAttrs systems;
-      pkgsFor = system: clan-core.inputs.nixpkgs.legacyPackages.${system};
-      treefmtFor = system: inputs.treefmt-nix.lib.evalModule (pkgsFor system) ./fmt.nix;
-    in
-    {
-      inherit (clan.config) nixosConfigurations nixosModules clanInternals;
-      clan = clan.config;
 
-      # `nix fmt` and the `nix flake check` formatting gate.
-      formatter = forAllSystems (system: (treefmtFor system).config.build.wrapper);
-      checks = forAllSystems (system: {
-        formatting = (treefmtFor system).config.build.check self;
-      });
+      flake = {
+        inherit (clan.config) nixosConfigurations nixosModules clanInternals;
+        clan = clan.config;
+      };
 
-      # Add the Clan cli tool to the dev shell.
-      # Use "nix develop" to enter the dev shell.
-      devShells = forAllSystems (
-        system:
+      perSystem =
+        { system, ... }:
         let
+          pkgs = clan-core.inputs.nixpkgs.legacyPackages.${system};
+          treefmtEval = inputs.treefmt-nix.lib.evalModule pkgs ./fmt.nix;
           clanCli = clan-core.packages.${system}.clan-cli;
           # `clan machines update a b c` normally runs machines in parallel,
           # which interleaves their output and buries the YubiKey PIN prompts.
           # This wrapper (first in PATH) runs them one at a time instead; any
           # flags fall through to the real CLI untouched.
-          clanSequential = (pkgsFor system).writeShellScriptBin "clan" ''
+          clanSequential = pkgs.writeShellScriptBin "clan" ''
             if [ "$#" -gt 3 ] && [ "$1" = machines ] && [ "$2" = update ]; then
               shift 2
               for arg in "$@"; do
@@ -84,14 +80,19 @@
           '';
         in
         {
-          default = (pkgsFor system).mkShell {
+          # `nix fmt` and the `nix flake check` formatting gate.
+          formatter = treefmtEval.config.build.wrapper;
+          checks.formatting = treefmtEval.config.build.check self;
+
+          # Add the Clan cli tool to the dev shell.
+          # Use "nix develop" to enter the dev shell.
+          devShells.default = pkgs.mkShell {
             packages = [
               clanSequential
               clanCli
-              (treefmtFor system).config.build.wrapper
+              treefmtEval.config.build.wrapper
             ];
           };
-        }
-      );
+        };
     };
 }