Add treefmt for code formatting

flake.lock

@@ -96,6 +96,22 @@
         "type": "github"
       }
     },
+    "nixpkgs_3": {
+      "locked": {
+        "lastModified": 1726871744,
+        "narHash": "sha256-V5LpfdHyQkUF7RfOaDPrZDP+oqz88lTJrMT1+stXNwo=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "a1d92660c6b3b7c26fb883500a80ea9d33321be2",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "advisory-db": "advisory-db",
@@ -103,7 +119,8 @@
         "flake-utils": "flake-utils",
         "nix-filter": "nix-filter",
         "nixpkgs": "nixpkgs",
-        "rust-overlay": "rust-overlay"
+        "rust-overlay": "rust-overlay",
+        "treefmt-nix": "treefmt-nix"
       }
     },
     "rust-overlay": {
@@ -138,6 +155,24 @@
         "repo": "default",
         "type": "github"
       }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": "nixpkgs_3"
+      },
+      "locked": {
+        "lastModified": 1729242555,
+        "narHash": "sha256-6jWSWxv2crIXmYSEb3LEVsFkCkyVHNllk61X4uhqfCs=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "d986489c1c757f6921a48c1439f19bfb9b8ecab5",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -9,6 +9,7 @@
     nix-filter.url = "github:numtide/nix-filter";
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
     rust-overlay.url = "github:oxalica/rust-overlay";
+    treefmt-nix.url = "github:numtide/treefmt-nix";
   };
 
   outputs =
@@ -20,6 +21,7 @@
       nix-filter,
       nixpkgs,
       rust-overlay,
+      treefmt-nix,
     }:
     flake-utils.lib.eachDefaultSystem (
       system:
@@ -54,23 +56,25 @@
         };
 
         commonArgs = {
-          inherit
-            src
-            stdenv
-            nativeBuildInputs
-            ;
+          inherit src stdenv nativeBuildInputs;
           strictDeps = true;
           LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";
         };
 
         cargoArtifacts = craneLib.buildDepsOnly commonArgs;
 
-        my-project = craneLib.buildPackage (
-          commonArgs
-          // {
-            inherit cargoArtifacts;
-          }
-        );
+        treefmtEval = treefmt-nix.lib.evalModule pkgs {
+          projectRootFile = "flake.nix";
+          programs = {
+            nixfmt.enable = true;
+            nixfmt.package = pkgs.nixfmt-rfc-style;
+            shfmt.enable = true;
+            rustfmt.enable = true;
+          };
+          settings.formatter.rustfmt.command = pkgs.lib.mkForce "${pkgs.rust-toolchain}/bin/rustfmt";
+        };
+
+        my-project = craneLib.buildPackage (commonArgs // { inherit cargoArtifacts; });
       in
       rec {
         # `nix build`
@@ -100,8 +104,8 @@
           );
         };
 
-        # Formatter for the Nix code
-        formatter = pkgs.nixpkgs-fmt;
+        # For `nix fmt`
+        formatter = treefmtEval.config.build.wrapper;
 
         # `nix develop`
         devShells.default = pkgs.mkShell {

justfile

@@ -10,11 +10,11 @@ check:
 
 # Lint all source code
 lint:
- echo FIXME: Add linter(s) here
+ cargo clippy
 
 # Format all source code
 fmt:
- echo FIXME: Add formatter here
+ nix fmt
 
 # Update all dependencies
 update: update-nix-pkgs update-rust-deps