feat: configure a pipeline for formatting nix code

Relies on a fork of treefmt-nix until it can be merged.

Signed-off-by: Brian McGee <brian@bmcgee.ie>

flake.lock

@@ -208,15 +208,16 @@
         ]
       },
       "locked": {
-        "lastModified": 1707300477,
+        "lastModified": 1714382886,
-        "narHash": "sha256-qQF0fEkHlnxHcrKIMRzOETnRBksUK048MXkX0SOmxvA=",
+        "narHash": "sha256-+gooxbbYcP+MORKQ7W/C2ATvlonW+dyHgCUPnu5dfco=",
-        "owner": "numtide",
+        "owner": "brianmcgee",
         "repo": "treefmt-nix",
-        "rev": "ac599dab59a66304eb511af07b3883114f061b9d",
+        "rev": "535e6904c34964ce56d8c092835c11fe6341acc8",
         "type": "github"
       },
       "original": {
-        "owner": "numtide",
+        "owner": "brianmcgee",
+        "ref": "feat/pipelines",
         "repo": "treefmt-nix",
         "type": "github"
       }

flake.nix

@@ -7,7 +7,8 @@
     flake-parts.url = "github:hercules-ci/flake-parts";
     flake-root.url = "github:srid/flake-root";
     treefmt-nix = {
-      url = "github:numtide/treefmt-nix";
+      # todo switch back to numtide/treefmt-nix once merged
+      url = "github:brianmcgee/treefmt-nix/feat/pipelines";
       inputs.nixpkgs.follows = "nixpkgs";
     };
     devshell = {

nix/treefmt.nix

@@ -22,20 +22,37 @@
         statix.enable = true;
       };
 
-      settings.formatter.prettier = {
+      settings.formatter = {
-        options = ["--tab-width" "4"];
+        deadnix = {
-        includes = [
+          pipeline = "nix";
-          "*.css"
+          priority = 1;
-          "*.html"
+        };
-          "*.js"
+
-          "*.json"
+        statix = {
-          "*.jsx"
+          pipeline = "nix";
-          "*.md"
+          priority = 2;
-          "*.mdx"
+        };
-          "*.scss"
+
-          "*.ts"
+        alejandra = {
-          "*.yaml"
+          pipeline = "nix";
-        ];
+          priority = 3;
+        };
+
+        prettier = {
+          options = ["--tab-width" "4"];
+          includes = [
+            "*.css"
+            "*.html"
+            "*.js"
+            "*.json"
+            "*.jsx"
+            "*.md"
+            "*.mdx"
+            "*.scss"
+            "*.ts"
+            "*.yaml"
+          ];
+        };
       };
     };