chore: add treefmt formatting (nix fmt + pre-commit + CI check)

.github/workflows/ci.yml

@@ -24,4 +24,7 @@ jobs:
  run: if [ -f scripts/test ]; then nix develop -c bash ./scripts/test; fi
 
  - name: Luacheck
- run: nix develop -c luacheck --quiet --std lua51 --no-unused-args src/
+ run: nix develop -c luacheck --quiet --std lua51 --no-unused-args --max-line-length 130 src/
+
+ - name: Format check
+ run: nix fmt && git diff --exit-code

.gitignore

@@ -1,4 +1,6 @@
 /.*
 !/.gitignore
 !/.github/
+!/.tidyrc.json
+!/.lua-format
 /output/

.lua-format

@@ -0,0 +1,10 @@
+# LuaFormatter config for the hand-written FFI under src/.
+# 2-space indent. Keep simple functions on one line; column_limit sits a few
+# columns under luacheck's 130 limit because lua-format under-counts the leading
+# indent and trailing comma, so this keeps every emitted line within 130.
+indent_width: 2
+use_tab: false
+column_limit: 126
+continuation_indent_width: 2
+keep_simple_function_one_line: true
+keep_simple_control_block_one_line: true

.tidyrc.json

@@ -0,0 +1,10 @@
+{
+ "importSort": "source",
+ "importWrap": "source",
+ "indent": 2,
+ "operatorsFile": null,
+ "ribbon": 1,
+ "typeArrowPlacement": "first",
+ "unicode": "source",
+ "width": 80
+}

AGENTS.md

@@ -4,11 +4,21 @@ A PureScript→Lua FFI fork in the [`purescript-lua`](https://github.com/purescr
 
 ## Commands
 
-All commands run inside the nix dev shell:
-
 - Build: `nix develop -c ./scripts/build`
 - Test (only if the fork has `scripts/test`): `nix develop -c bash ./scripts/test`
-- Lint: `nix develop -c luacheck --quiet --std lua51 --no-unused-args src/`
+- Lint: `nix develop -c luacheck --quiet --std lua51 --no-unused-args --max-line-length 130 src/`
+- Format: `nix fmt` (check: `nix fmt && git diff --exit-code`)
+
+## Formatting
+
+`nix fmt` runs treefmt (`treefmt.nix`): nixfmt for Nix, `dhall format`, purs-tidy
+for `*.purs` (config in `.tidyrc.json`), and LuaFormatter for the `*.lua` FFI
+(config in `.lua-format`). LuaFormatter is used over StyLua because it keeps the
+parentheses pslua's foreign-file parser requires. The Lua line budget is 130
+columns, matching the `luacheck --max-line-length` above. The check is
+content-based (`nix fmt && git diff --exit-code`) rather than `treefmt --ci`,
+since the in-place formatters bump mtime even when content is unchanged, which
+trips treefmt's `--fail-on-change`. CI and the pre-commit hook use it.
 
 ## Lua 5.1 target
 

flake.nix

@@ -9,16 +9,33 @@
  inputs.nixpkgs.follows = "nixpkgs";
  };
  pslua.url = "github:purescript-lua/purescript-lua";
+ treefmt-nix = {
+ url = "github:numtide/treefmt-nix";
+ inputs.nixpkgs.follows = "nixpkgs";
+ };
  };
 
- outputs = { self, nixpkgs, flake-utils, purescript-overlay, pslua }:
- flake-utils.lib.eachDefaultSystem (system:
+ outputs =
+ {
+ self,
+ nixpkgs,
+ flake-utils,
+ purescript-overlay,
+ pslua,
+ treefmt-nix,
+ }:
+ flake-utils.lib.eachDefaultSystem (
+ system:
  let
  pkgs = import nixpkgs {
  inherit system;
  overlays = [ purescript-overlay.overlays.default ];
  };
- in {
+ treefmtEval = treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
+ in
+ {
+ formatter = treefmtEval.config.build.wrapper;
+ checks.formatting = treefmtEval.config.build.check self;
  devShell = pkgs.mkShell {
  buildInputs = with pkgs; [
  dhall
@@ -31,8 +48,26 @@
  spago-bin.spago-0_21_0
  treefmt
  ];
+ # Install a content-based pre-commit hook. It compares the working
+ # tree diff before and after `nix fmt`, so it only objects to changes
+ # the formatter itself introduces (not the developer's existing
+ # unstaged work) and is not fooled by formatters that only bump mtime.
+ # Rewritten each shell entry to stay in sync with this flake.
+ shellHook = ''
+ hook=.git/hooks/pre-commit
+ if [ -d .git ]; then
+ printf '%s\n' \
+ '#!/usr/bin/env bash' \
+ 'before=$(git diff)' \
+ 'nix fmt >/dev/null 2>&1 || exit 0' \
+ '[ "$before" = "$(git diff)" ] || { echo "nix fmt changed files; re-stage them, then commit." >&2; exit 1; }' \
+ > "$hook"
+ chmod +x "$hook"
+ fi
+ '';
  };
- });
+ }
+ );
 
  # --- Flake Local Nix Configuration ----------------------------
  nixConfig = {

src/Control/Monad/ST/Internal.purs

@@ -66,12 +66,12 @@ instance monadRecST :: MonadRec (ST r) where
  Done _ -> pure unit
  fromDone <$> read r
  where
-fromDone :: forall a b. Step a b -> b
-fromDone = unsafePartial \(Done b) -> b
+ fromDone :: forall a b. Step a b -> b
+ fromDone = unsafePartial \(Done b) -> b
 
-isLooping = case _ of
-Loop _ -> true
-_ -> false
+ isLooping = case _ of
+ Loop _ -> true
+ _ -> false
 
 instance semigroupST :: Semigroup a => Semigroup (ST r a) where
  append = lift2 append
@@ -122,10 +122,12 @@ foreign import read :: forall a r. STRef r a -> ST r a
 -- | Update the value of a mutable reference by applying a function
 -- | to the current value, computing a new state value for the reference and
 -- | a return value.
-modify' :: forall r a b. (a -> { state :: a, value :: b }) -> STRef r a -> ST r b
+modify'
+ :: forall r a b. (a -> { state :: a, value :: b }) -> STRef r a -> ST r b
 modify' = modifyImpl
 
-foreign import modifyImpl :: forall r a b. (a -> { state :: a, value :: b }) -> STRef r a -> ST r b
+foreign import modifyImpl
+ :: forall r a b. (a -> { state :: a, value :: b }) -> STRef r a -> ST r b
 
 -- | Modify the value of a mutable reference by applying a function to the
 -- | current value. The modified value is returned.

src/Control/Monad/ST/Uncurried.lua

@@ -17,9 +17,7 @@ return {
 
  mkSTFn9 = (function(fn) return function(a, b, c, d, e, f, g, h, i) return fn(a)(b)(c)(d)(e)(f)(g)(h)(i)() end end),
 
- mkSTFn10 = (function(fn)
- return function(a, b, c, d, e, f, g, h, i, j) return fn(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)() end
- end),
+ mkSTFn10 = (function(fn) return function(a, b, c, d, e, f, g, h, i, j) return fn(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)() end end),
 
  runSTFn1 = (function(fn) return function(a) return function() return fn(a) end end end),
 
@@ -38,9 +36,7 @@ return {
  runSTFn5 = (function(fn)
  return function(a)
  return function(b)
- return function(c)
- return function(d) return function(e) return function() return fn(a, b, c, d, e) end end end
- end
+ return function(c) return function(d) return function(e) return function() return fn(a, b, c, d, e) end end end end
  end
  end
  end),
@@ -63,9 +59,7 @@ return {
  return function(c)
  return function(d)
  return function(e)
- return function(f)
- return function(g) return function() return fn(a, b, c, d, e, f, g) end end
- end
+ return function(f) return function(g) return function() return fn(a, b, c, d, e, f, g) end end end
  end
  end
  end
@@ -121,9 +115,7 @@ return {
  return function(g)
  return function(h)
  return function(i)
- return function(j)
- return function() return fn(a, b, c, d, e, f, g, h, i, j) end
- end
+ return function(j) return function() return fn(a, b, c, d, e, f, g, h, i, j) end end
  end
  end
  end