add treefmt

flake.lock

@@ -55,7 +55,28 @@
     "root": {
       "inputs": {
         "flake-parts": "flake-parts",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1693817438,
+        "narHash": "sha256-fg3+n4Ky1gCzDtPm0MomMTFw0YkH05Y8ojy5t7bkfHg=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "b8d3a059f5487d6767d07c3716386753e3132d9f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
       }
     }
   },

flake.nix

@@ -4,10 +4,14 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     flake-parts.url = "github:hercules-ci/flake-parts";
+
+    treefmt-nix.url = "github:numtide/treefmt-nix";
+    treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
   };
 
   outputs = inputs@{ flake-parts, ... }:
     flake-parts.lib.mkFlake { inherit inputs; } ({ lib, ... }: {
+      imports = [ ./treefmt.nix ];
       systems = [
         "aarch64-linux"
         "x86_64-linux"
@@ -16,8 +20,15 @@
         "aarch64-darwin"
       ];
       perSystem = { pkgs, self', ... }: {
-        packages.nix-ci-builds = pkgs.callPackage ./default.nix {};
+        packages.nix-ci-builds = pkgs.callPackage ./default.nix { };
         packages.default = self'.packages.nix-ci-builds;
+
+        checks =
+          let
+            packages = lib.mapAttrs' (n: lib.nameValuePair "package-${n}") self'.packages;
+            devShells = lib.mapAttrs' (n: lib.nameValuePair "devShell-${n}") self'.devShells;
+          in
+          packages // devShells;
       };
     });
 }

treefmt.nix

@@ -0,0 +1,44 @@
+{ lib, inputs, ... }: {
+  imports = [
+    inputs.treefmt-nix.flakeModule
+  ];
+
+  perSystem = { pkgs, ... }: {
+    treefmt = {
+      # Used to find the project root
+      projectRootFile = "flake.lock";
+
+      programs.mypy.enable = true;
+
+      settings.formatter = {
+        nix = {
+          command = "sh";
+          options = [
+            "-eucx"
+            ''
+              # First deadnix
+              ${lib.getExe pkgs.deadnix} --edit "$@"
+              # Then nixpkgs-fmt
+              ${lib.getExe pkgs.nixpkgs-fmt} "$@"
+            ''
+            "--"
+          ];
+          includes = [ "*.nix" ];
+        };
+
+        python = {
+          command = "sh";
+          options = [
+            "-eucx"
+            ''
+              ${lib.getExe pkgs.ruff} --fix "$@"
+              ${lib.getExe pkgs.black} "$@"
+            ''
+            "--" # this argument is ignored by bash
+          ];
+          includes = [ "*.py" ];
+        };
+      };
+    };
+  };
+}