flake: add treefmt

Author: jaen

flake.lock

@@ -8,10 +8,22 @@
     androidPkgs.url = "github:tadfisher/android-nixpkgs/stable";
 
     flake-compat.url = "github:nix-community/flake-compat";
+
+    treefmt-nix.url = "github:numtide/treefmt-nix";
+    treefmt-nix.inputs.nixpkgs.follows = "nixpkgs-unstable";
   };
 
-  outputs = { self, nixpkgs, nixpkgs-unstable, androidPkgs, flake-compat,  ... }@inputs: let
+  outputs = { self, nixpkgs, nixpkgs-unstable, androidPkgs, flake-compat, treefmt-nix, ... }@inputs: let
     pkgs = import ./pkgs/default.nix { inherit inputs; };
+    
+    treeFmt = treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
+    pythonForUpdaterScripts = pkgs.python3.withPackages (
+      p: with p; [
+        mypy
+        flake8
+        pytest
+      ]
+    );
   in {
     # robotnixSystem evaluates a robotnix configuration
     lib.robotnixSystem = configuration: import ./default.nix {
@@ -33,9 +45,9 @@
 
     devShell.x86_64-linux = pkgs.mkShell {
       name = "robotnix-scripts";
+      inputsFrom = [ treeFmt.config.build.devShell ];
       nativeBuildInputs = with pkgs; [
-        # For android updater scripts
-        (python3.withPackages (p: with p; [ mypy flake8 pytest ]))
+        pythonForUpdaterScripts
         gitRepo nix-prefetch-git
         curl pup jq
         shellcheck
@@ -49,5 +61,11 @@
       ];
       PYTHONPATH=./scripts;
     };
+
+    formatter.x86_64-linux = treeFmt.config.build.wrapper;
+
+    checks.x86_64-linux = {
+      formatting = treeFmt.config.build.check self;
+    };
   };
 }

flake.nix

@@ -1,4 +1,9 @@
 { inputs }:
+let
+  inherit (inputs) nixpkgs-unstable;
+
+  unstablePkgs = nixpkgs-unstable.legacyPackages.x86_64-linux;
+in
 self: super: {
   android-emulator = super.callPackage ./android-emulator {};
 
@@ -36,6 +41,8 @@ self: super: {
 
   gitRepo = super.callPackage ./gitRepo { inherit inputs; };
 
+  nixfmt-rfc-style = unstablePkgs.nixfmt-rfc-style;
+
   ###
 
   # Robotnix helper derivations

pkgs/overlay.nix

@@ -0,0 +1,45 @@
+{ pkgs, lib, ... }:
+{
+  # Adding this options is a workaround for `config.build.programs` not evaluating properly
+  # to get all formatter binaries into a devShell
+  options.programs.mypy.package = lib.mkPackageOption pkgs  [ "python3Packages" "mypy" ] { };
+  config = {
+    projectRootFile = "flake.nix";
+
+    programs = {
+      nixpkgs-fmt.enable = true;
+      nixpkgs-fmt.package = pkgs.nixfmt-rfc-style;
+
+      mypy.enable = true;
+      mypy.package = pkgs.python3.withPackages(ps: with ps; [ mypy pytest ]);
+      mypy.directories = {
+        "." = {
+          # Fot whatever reason using `settings.formatter.mypy.excludes` does not work properly
+          options = [ "--exclude" "apks/chromium" "--exclude" "result" ];
+          # Has to be set again, because treefmt clears PYTHONPATH and running via `treefmt` fails, see:
+          # https://github.com/numtide/treefmt-nix/blob/main/programs/mypy.nix#L67
+          extraPythonPackages = [ pkgs.python3Packages.pytest ];
+        };
+      };
+
+      # Drop–in flake8 replacement
+      ruff.format = true;
+      ruff.check = true;
+
+      shfmt.enable = true;
+
+      shellcheck.enable = true;
+    };
+
+    settings.formatter = {
+      ruff-check.excludes = [ "apks/chromium/*" ];
+      ruff-format.excludes = [ "apks/chromium/*" ];
+      shellcheck.includes = lib.mkForce [
+        "flavors/**/*.sh"
+        "modules/pixel/update.sh"
+        "scripts/patchelf-prefix.sh"
+        "pkgs/robotnix/unpack-images.sh"
+      ];
+    };
+  };
+}