1 files changed, 60 insertions, 0 deletions
diff --git a/tools/depotfmt.nix b/tools/depotfmt.nix
new file mode 100644
index 000000000000..dbd3a31a0d80
--- /dev/null
+++ b/tools/depotfmt.nix
@@ -0,0 +1,60 @@
+# Builds treefmt for depot, with a hardcoded configuration that
+# includes the right paths to formatters.
+{ depot, pkgs, ... }:
+
+let
+  # terraform fmt can't handle multiple paths at once, but treefmt
+  # expects this
+  terraformat = pkgs.writeShellScript "terraformat" ''
+    echo "$@" | xargs -n1 ${pkgs.terraform}/bin/terraform fmt
+  '';
+
+  config = pkgs.writeText "depot-treefmt-config" ''
+    [formatter.go]
+    command = "${pkgs.go}/bin/gofmt"
+    options = [ "-w" ]
+    includes = ["*.go"]
+
+    [formatter.tf]
+    command = "${terraformat}"
+    includes = [ "*.tf" ]
+
+    [formatter.nix]
+    command = "${pkgs.nixpkgs-fmt}/bin/nixpkgs-fmt"
+    includes = [ "*.nix" ]
+    excludes = [
+      "third_party/nix/tests/*",
+      "third_party/nix/src/tests/*"
+    ]
+
+    [formatter.rust]
+    command = "${pkgs.rustfmt}/bin/rustfmt"
+    includes = [ "*.rs" ]
+    excludes = [
+      "users/tazjin/*",
+    ]
+  '';
+
+  # helper tool for formatting the depot interactively
+  depotfmt = pkgs.writeShellScriptBin "depotfmt" ''
+    exec ${pkgs.treefmt}/bin/treefmt ''${@} \
+      --config-file ${config} \
+      --tree-root $(${pkgs.git}/bin/git rev-parse --show-toplevel)
+  '';
+
+  # wrapper script for running formatting checks in CI
+  check = pkgs.writeShellScript "depotfmt-check" ''
+    ${pkgs.treefmt}/bin/treefmt \
+      --clear-cache \
+      --fail-on-change \
+      --config-file ${config} \
+      --tree-root .
+  '';
+in
+depotfmt.overrideAttrs (_: {
+  passthru.meta.ci.extraSteps.check = {
+    label = "depot formatting check";
+    command = check;
+    alwaysRun = true;
+  };
+})