chore: Add treefmt

.github/workflows/ci.yml

@@ -19,30 +19,6 @@ jobs:
     - name: Check format
       run: nix-shell --packages jq diffutils --run "diff --unified overrides/build-systems.json <(jq --from-file overrides/sort-build-systems.jq --raw-output --sort-keys < overrides/build-systems.json)"
 
-  nixpkgs-fmt:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: cachix/install-nix-action@v23
-      with:
-        nix_path: nixpkgs=channel:nixos-unstable
-    - uses: actions/checkout@v4
-    - name: Check format
-      run: nix run 'nixpkgs#nixpkgs-fmt' -- --check .
-
-  black-fmt:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: cachix/install-nix-action@v23
-      with:
-        nix_path: nixpkgs=channel:nixos-unstable
-    - uses: actions/checkout@v4
-    - uses: cachix/cachix-action@v12
-      with:
-        name: poetry2nix
-        signingKey: "VhaWuN3IyJVpWg+aZvTocVB+W8ziZKKRGLKR53Pkld3YRZxYOUfXZf0fvqF+LkqVW0eA60trVd5vsqNONpX9Hw=="
-    - name: Check format
-      run: nix develop -c black --check .
-
   nix-matrix:
     runs-on: ubuntu-latest
     outputs:
@@ -74,8 +50,6 @@ jobs:
   collect:
     runs-on: ubuntu-latest
     needs:
-      - nixpkgs-fmt
-      - black-fmt
       - nix-build
       - sort-build-systems
     steps:

dev/treefmt.nix

@@ -0,0 +1,31 @@
+{ pkgs, ... }: {
+  # Used to find the project root
+  projectRootFile = "flake.lock";
+
+  settings.formatter = {
+    nix = {
+      command = "sh";
+      options = [
+        "-eucx"
+        ''
+          ${pkgs.lib.getExe pkgs.nixpkgs-fmt} "$@"
+        ''
+        "--"
+      ];
+      includes = [ "*.nix" ];
+      excludes = [ ];
+    };
+
+    python = {
+      command = "sh";
+      options = [
+        "-eucx"
+        ''
+          ${pkgs.lib.getExe pkgs.python3.pkgs.black} "$@"
+        ''
+        "--" # this argument is ignored by bash
+      ];
+      includes = [ "*.py" ];
+    };
+  };
+}

flake.nix

@@ -5,13 +5,21 @@
     flake-utils.url = "github:numtide/flake-utils";
     nixpkgs.url = "github:NixOS/nixpkgs/master";
 
+    treefmt-nix.url = "github:numtide/treefmt-nix";
+    treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
+
     nix-github-actions = {
       url = "github:nix-community/nix-github-actions";
       inputs.nixpkgs.follows = "nixpkgs";
     };
   };
 
-  outputs = { self, nixpkgs, flake-utils, nix-github-actions }:
+  outputs = { self, nixpkgs, flake-utils, nix-github-actions, treefmt-nix, systems }:
+    let
+      eachSystem = f: nixpkgs.lib.genAttrs (import systems) (system: f nixpkgs.legacyPackages.${system});
+      treefmtEval = eachSystem (pkgs: treefmt-nix.lib.evalModule pkgs ./dev/treefmt.nix);
+    in
+
     {
       overlay = import ./overlay.nix;
 
@@ -32,7 +40,9 @@
               let
                 pkgs = mkPkgs "x86_64-linux";
               in
-              import ./tests { inherit pkgs; };
+              import ./tests { inherit pkgs; } // {
+                formatting = treefmtEval.x86_64-linux.config.build.check self;
+              };
 
             x86_64-darwin =
               let
@@ -84,6 +94,8 @@
         poetry2nix = import ./default.nix { inherit pkgs; };
       in
       rec {
+        formatter = treefmtEval.${system}.config.build.wrapper;
+
         packages = {
           poetry2nix = poetry2nix.cli;
           default = poetry2nix.cli;