[INTT-54] Add code formatters for general projects

flake.nix

@@ -25,6 +25,11 @@
       url = "github:BirdeeHub/nix-wrapper-modules";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    treefmt = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =

nix/default.nix

@@ -8,6 +8,7 @@ importingFlake: {
   imports = [
     inputs.devshell.flakeModule
     inputs.github-actions-nix.flakeModules.default
+    inputs.treefmt.flakeModule
     flakeModules.prek-pre-commit
 
     (importApply ./general args)

nix/general/default.nix

@@ -8,6 +8,7 @@ importingFlake: {
   imports = [
     ./action-versions.nix
     (importApply ./devshell.nix args)
+    ./formatting.nix
     (importApply ./pre-commit-hooks.nix args)
 
     ./workflows/check-pre-commit-hooks.nix

nix/general/devshell.nix

@@ -5,31 +5,40 @@
   ...
 }:
 importingFlake: {
-  config.perSystem = { config, ... }: {
-    devshells.standards = {
-      name = lib.mkDefault "engineering-standards";
+  config.perSystem =
+    { config, pkgs, ... }:
+    {
+      devshells.standards = {
+        name = lib.mkDefault "engineering-standards";
 
       # Include all packages from pre-commit in the shell
-      # - This allows easy access to the individual checks, if developers are interested in running them
-      # - `prek install` doesn't install the wrapped binary, so when executing the hooks, all runtimePkgs
-      #   would be missing if they were not in the shell
-      packages = builtins.map (package: package.data) config.prek-pre-commit.package.runtimePkgs;
+          # - This allows easy access to the individual checks, if developers are interested in running them
+          # - `prek install` doesn't install the wrapped binary, so when executing the hooks, all runtimePkgs
+          #   would be missing if they were not in the shell
+          packages = builtins.map (package: package.data) config.prek-pre-commit.package.runtimePkgs;
 
       commands = [
-        {
-          name = "prek";
-          help = "Run pre-commit hooks on currently staged changes";
-          category = "[[lints and checks]]";
-          package = config.prek-pre-commit.package.wrapper;
-        }
+          {
+            name = "nix fmt";
+            help = "Auto-format all files in the project.";
+            category = "[[lints and checks]]";
+            package = pkgs.nix;
+          }
 
-        {
-          name = "prek -s main -o HEAD";
-          help = "Run pre-commit hooks on all commits in the current branch";
-          category = "[[lints and checks]]";
-          package = config.prek-pre-commit.package.wrapper;
-        }
-      ];
+          {
+            name = "prek";
+            help = "Run pre-commit hooks on currently staged changes";
+            category = "[[lints and checks]]";
+            package = config.prek-pre-commit.package.wrapper;
+          }
+
+            {
+              name = "prek -s main -o HEAD";
+              help = "Run pre-commit hooks on all commits in the current branch";
+              category = "[[lints and checks]]";
+              package = config.prek-pre-commit.package.wrapper;
+            }
+          ];
+      };
     };
-  };
 }

nix/general/formatting.nix

@@ -0,0 +1,34 @@
+{
+  perSystem =
+    { config, ... }:
+    {
+      treefmt = {
+        # `prek` is in charge of running these kinds of checks, we don't
+        # want to run formatters with `nix flake check`.
+        flakeCheck = false;
+
+        settings = {
+          allowMissingFormatter = false;
+          walk = "git";
+
+          excludes = config.filegen.generatedFiles;
+        };
+
+        programs = {
+          prettier.enable = true;
+          sqlfluff.enable = true;
+          shfmt.enable = true;
+        };
+
+        settings.formatter.prettier.excludes = [ "*.md" ];
+      };
+
+      filegen.settings.files = [
+        {
+          type = "copy";
+          target = "treefmt.toml";
+          source = config.treefmt.build.configFile;
+        }
+      ];
+    };
+}