chore: add treefmt - to format them all

- this is a unified & modern approch to keeping all files according to fmt-spec
- has excellent editor integration

flake.lock

@@ -21,6 +21,21 @@
         "type": "github"
       }
     },
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1610051610,
+        "narHash": "sha256-U9rPz/usA1/Aohhk7Cmc2gBrEEKRzcW4nwPWMPwja4Y=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "3982c9903e93927c2164caa727cd3f6a0e6d14cc",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
     "flakeCompat": {
       "flake": false,
       "locked": {
@@ -73,7 +88,8 @@
         "fenix": "fenix",
         "flakeCompat": "flakeCompat",
         "flakeUtils": "flakeUtils",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "treefmt": "treefmt"
       }
     },
     "rust-analyzer-src": {
@@ -92,6 +108,27 @@
         "repo": "rust-analyzer",
         "type": "github"
       }
+    },
+    "treefmt": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1640364438,
+        "narHash": "sha256-sV1Oa9JVNmpAwZ4cnVs7ovHrKL8EPg3J08jPX/a48LI=",
+        "owner": "numtide",
+        "repo": "treefmt",
+        "rev": "26d7f5f15e5d22d4413ba7c5ae0447fdc0b5cc76",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -5,6 +5,8 @@
     flakeCompat.url = github:edolstra/flake-compat;
     flakeCompat.flake = false;
     flakeUtils.url = "github:numtide/flake-utils";
+    treefmt.url = "github:numtide/treefmt";
+    treefmt.inputs.nixpkgs.follows = "nixpkgs";
     nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
   };
   outputs =
@@ -15,6 +17,7 @@
         let
           nixpkgs = import inputs.nixpkgs { inherit system; };
           cargoToml = builtins.fromTOML ( builtins.readFile ./Cargo.toml );
+          treefmt = inputs.treefmt.defaultPackage.${ system };
           fenix = inputs.fenix.packages.${ system };
           fenixPlatform = nixpkgs.makeRustPlatform { inherit ( fenix.latest ) cargo rustc; };
         in
@@ -53,7 +56,11 @@
                   fenix.latest.rust-src
                   fenix.latest.rustc
                   fenix.latest.rustfmt
+                  treefmt
+                  nixpkgs.shfmt
+                  nixpkgs.nodePackages.prettier
                 ];
+                shellHook = "cargo build";
               };
         }
       );

treefmt.toml

@@ -0,0 +1,32 @@
+# One CLI to format the code tree - https://github.com/numtide/treefmt
+
+[formatter.nix]
+command = "./target/debug/alejandra"
+includes = ["*.nix"]
+
+[formatter.prettier]
+command = "prettier"
+options = ["--write"]
+includes = [
+    "*.css",
+    "*.html",
+    "*.js",
+    "*.json",
+    "*.jsx",
+    "*.md",
+    "*.mdx",
+    "*.scss",
+    "*.ts",
+    "*.yaml",
+]
+
+[formatter.shell]
+command = "shfmt"
+options = [
+    "-i",
+    "2",  # indent 2
+    "-s",  # simplify the code
+    "-w",  # write back to the file
+]
+includes = ["*.sh"]
+