Switch to treefmt; resolves #283

.github/workflows/ci.yaml

@@ -16,6 +16,12 @@ jobs:
           install_options: "--tarball-url-prefix https://nixos-nix-install-tests.cachix.org/serve"
           extra_nix_config: |
             experimental-features = nix-command flakes
+      - name: Cache Nix dependencies
+        run: |
+          nix develop -j 4 -c echo
+      - name: Format check
+        run: |
+          nix develop -j auto -c treefmt -- --fail-on-change
       - name: Build
         id: build
         run: |

.vscode/extensions.json

@@ -5,6 +5,7 @@
     "haskell.haskell",
     "arrterian.nix-env-selector",
     "bbenoist.nix",
-    "jnoortheen.nix-ide"
+    "jnoortheen.nix-ide",
+    "tamasfe.even-better-toml"
   ]
 }

flake.lock

@@ -31,43 +31,6 @@
         "type": "github"
       }
     },
-    "flake-utils_2": {
-      "locked": {
-        "lastModified": 1644229661,
-        "narHash": "sha256-1YdnJAsNy69bpcjuoKdOYQX0YxZBiCYZo4Twxerqv7k=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "3cecb5b042f7f209c56ffd8371b2711a290ec797",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
-    "lint-utils": {
-      "inputs": {
-        "flake-utils": "flake-utils_2",
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1650427214,
-        "narHash": "sha256-9m66rRSSM614ocRXNPAArwnrS6zzCQYYhd3nw8g4QUg=",
-        "ref": "overengineered",
-        "rev": "5555def5a25c5437834c06cbe79b3945916ec59f",
-        "revCount": 28,
-        "type": "git",
-        "url": "https://gitlab.homotopic.tech/nix/lint-utils.git"
-      },
-      "original": {
-        "ref": "overengineered",
-        "type": "git",
-        "url": "https://gitlab.homotopic.tech/nix/lint-utils.git"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1651024496,
@@ -88,7 +51,6 @@
       "inputs": {
         "flake-compat": "flake-compat",
         "flake-utils": "flake-utils",
-        "lint-utils": "lint-utils",
         "nixpkgs": "nixpkgs"
       }
     }

flake.nix

@@ -8,12 +8,6 @@
     flake-compat.url = "github:edolstra/flake-compat";
     flake-compat.flake = false;
     flake-compat.inputs.nixpkgs.follows = "nixpkgs";
-    lint-utils = {
-      type = "git";
-      url = "https://gitlab.homotopic.tech/nix/lint-utils.git";
-      ref = "overengineered"; # https://gitlab.homotopic.tech/nix/lint-utils/-/merge_requests/4
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
   };
 
   outputs = inputs:
@@ -39,6 +33,7 @@
             fourmolu
             hlint
             pkgs.nixpkgs-fmt
+            pkgs.treefmt
           ];
 
           project = returnShellEnv:
@@ -64,15 +59,6 @@
                       (optionals returnShellEnv shellDeps))
                   ];
             };
-
-          lintSpec = {
-            nixpkgs-fmt = { };
-            cabal-fmt = { };
-            # hlint = { };
-            fourmolu = {
-              ghcOpts = "-o-XTypeApplications -o-XImportQualifiedPost";
-            };
-          };
         in
         {
           # Used by `nix build ...`
@@ -85,7 +71,6 @@
               type = "app";
               program = "${inputs.self.packages.${system}.default}/bin/haskell-template";
             };
-            format = inputs.lint-utils.mkApp.${system} lintSpec;
           };
           # Used by `nix develop ...`
           devShells = {

treefmt.toml

@@ -0,0 +1,16 @@
+[formatter.haskell]
+command = "fourmolu"
+options = [
+    "--ghc-opt",
+    "-XImportQualifiedPost",
+    "--ghc-opt",
+    "-XTypeApplications",
+    "--mode",
+    "inplace",
+    "--check-idempotence",
+]
+includes = ["*.hs"]
+
+[formatter.nix]
+command = "nixpkgs-fmt"
+includes = ["*.nix"]