purescript-lua · Unisay · Jun 15, 2026 · Jun 14, 2026
diff --git a/.github/workflows/ci.yml b/.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
diff --git a/.gitignore b/.gitignore
@@ -1,4 +1,6 @@
 /.*
 !/.gitignore
 !/.github/
+!/.tidyrc.json
+!/.lua-format
 /output/
diff --git a/.lua-format b/.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
diff --git a/.tidyrc.json b/.tidyrc.json
@@ -0,0 +1,10 @@
+{
+  "importSort": "source",
+  "importWrap": "source",
+  "indent": 2,
+  "operatorsFile": null,
+  "ribbon": 1,
+  "typeArrowPlacement": "first",
+  "unicode": "source",
+  "width": 80
+}
diff --git a/AGENTS.md b/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
 

diff --git a/flake.lock b/flake.lock
diff --git a/flake.nix b/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 = {

diff --git a/src/Data/Function/Uncurried.lua b/src/Data/Function/Uncurried.lua
@@ -17,17 +17,16 @@ return {
   end),
   runFn5 = (function(fn)
     return function(a)
-      return function(b)
-        return function(c) return function(d) return function(e) return fn(a, b, c, d, e) end end end
-      end
+      return function(b) return function(c) return function(d) return function(e) return fn(a, b, c, d, e) end end end end
     end
   end),
   runFn6 = (function(fn)
     return function(a)
       return function(b)
-        return function(c)
-          return function(d) return function(e) return function(f) return fn(a, b, c, d, e, f) end end end
-        end
+        return
+          function(c)
+            return function(d) return function(e) return function(f) return fn(a, b, c, d, e, f) end end end
+          end
       end
     end
   end),
@@ -48,9 +47,7 @@ return {
         return function(c)
           return function(d)
             return function(e)
-              return function(f)
-                return function(g) return function(h) return fn(a, b, c, d, e, f, g, h) end end
-              end
+              return function(f) return function(g) return function(h) return fn(a, b, c, d, e, f, g, h) end end end
             end
           end
         end

diff --git a/src/Data/Function/Uncurried.purs b/src/Data/Function/Uncurried.purs
@@ -31,27 +31,62 @@ foreign import data Fn5 :: Type -> Type -> Type -> Type -> Type -> Type -> Type
 type role Fn5 representational representational representational representational representational representational
 
 -- | A function of six arguments
-foreign import data Fn6 :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
+foreign import data Fn6
+  :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
 
 type role Fn6 representational representational representational representational representational representational representational
 
 -- | A function of seven arguments
-foreign import data Fn7 :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
+foreign import data Fn7
+  :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
 
 type role Fn7 representational representational representational representational representational representational representational representational
 
 -- | A function of eight arguments
-foreign import data Fn8 :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
+foreign import data Fn8
+  :: Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
 
 type role Fn8 representational representational representational representational representational representational representational representational representational
 
 -- | A function of nine arguments
-foreign import data Fn9 :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
+foreign import data Fn9
+  :: Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
 
 type role Fn9 representational representational representational representational representational representational representational representational representational representational
 
 -- | A function of ten arguments
-foreign import data Fn10 :: Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type -> Type
+foreign import data Fn10
+  :: Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
+  -> Type
 
 type role Fn10 representational representational representational representational representational representational representational representational representational representational representational
 
@@ -69,25 +104,42 @@ foreign import mkFn2 :: forall a b c. (a -> b -> c) -> Fn2 a b c
 foreign import mkFn3 :: forall a b c d. (a -> b -> c -> d) -> Fn3 a b c d
 
 -- | Create a function of four arguments from a curried function
-foreign import mkFn4 :: forall a b c d e. (a -> b -> c -> d -> e) -> Fn4 a b c d e
+foreign import mkFn4
+  :: forall a b c d e. (a -> b -> c -> d -> e) -> Fn4 a b c d e
 
 -- | Create a function of five arguments from a curried function
-foreign import mkFn5 :: forall a b c d e f. (a -> b -> c -> d -> e -> f) -> Fn5 a b c d e f
+foreign import mkFn5
+  :: forall a b c d e f. (a -> b -> c -> d -> e -> f) -> Fn5 a b c d e f
 
 -- | Create a function of six arguments from a curried function
-foreign import mkFn6 :: forall a b c d e f g. (a -> b -> c -> d -> e -> f -> g) -> Fn6 a b c d e f g
+foreign import mkFn6
+  :: forall a b c d e f g
+   . (a -> b -> c -> d -> e -> f -> g)
+  -> Fn6 a b c d e f g
 
 -- | Create a function of seven arguments from a curried function
-foreign import mkFn7 :: forall a b c d e f g h. (a -> b -> c -> d -> e -> f -> g -> h) -> Fn7 a b c d e f g h
+foreign import mkFn7
+  :: forall a b c d e f g h
+   . (a -> b -> c -> d -> e -> f -> g -> h)
+  -> Fn7 a b c d e f g h
 
 -- | Create a function of eight arguments from a curried function
-foreign import mkFn8 :: forall a b c d e f g h i. (a -> b -> c -> d -> e -> f -> g -> h -> i) -> Fn8 a b c d e f g h i
+foreign import mkFn8
+  :: forall a b c d e f g h i
+   . (a -> b -> c -> d -> e -> f -> g -> h -> i)
+  -> Fn8 a b c d e f g h i
 
 -- | Create a function of nine arguments from a curried function
-foreign import mkFn9 :: forall a b c d e f g h i j. (a -> b -> c -> d -> e -> f -> g -> h -> i -> j) -> Fn9 a b c d e f g h i j
+foreign import mkFn9
+  :: forall a b c d e f g h i j
+   . (a -> b -> c -> d -> e -> f -> g -> h -> i -> j)
+  -> Fn9 a b c d e f g h i j
 
 -- | Create a function of ten arguments from a curried function
-foreign import mkFn10 :: forall a b c d e f g h i j k. (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k) -> Fn10 a b c d e f g h i j k
+foreign import mkFn10
+  :: forall a b c d e f g h i j k
+   . (a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k)
+  -> Fn10 a b c d e f g h i j k
 
 -- | Apply a function of no arguments
 foreign import runFn0 :: forall a. Fn0 a -> a
@@ -103,22 +155,71 @@ foreign import runFn2 :: forall a b c. Fn2 a b c -> a -> b -> c
 foreign import runFn3 :: forall a b c d. Fn3 a b c d -> a -> b -> c -> d
 
 -- | Apply a function of four arguments
-foreign import runFn4 :: forall a b c d e. Fn4 a b c d e -> a -> b -> c -> d -> e
+foreign import runFn4
+  :: forall a b c d e. Fn4 a b c d e -> a -> b -> c -> d -> e
 
 -- | Apply a function of five arguments
-foreign import runFn5 :: forall a b c d e f. Fn5 a b c d e f -> a -> b -> c -> d -> e -> f
+foreign import runFn5
+  :: forall a b c d e f. Fn5 a b c d e f -> a -> b -> c -> d -> e -> f
 
 -- | Apply a function of six arguments
-foreign import runFn6 :: forall a b c d e f g. Fn6 a b c d e f g -> a -> b -> c -> d -> e -> f -> g
+foreign import runFn6
+  :: forall a b c d e f g. Fn6 a b c d e f g -> a -> b -> c -> d -> e -> f -> g
 
 -- | Apply a function of seven arguments
-foreign import runFn7 :: forall a b c d e f g h. Fn7 a b c d e f g h -> a -> b -> c -> d -> e -> f -> g -> h
+foreign import runFn7
+  :: forall a b c d e f g h
+   . Fn7 a b c d e f g h
+  -> a
+  -> b
+  -> c
+  -> d
+  -> e
+  -> f
+  -> g
+  -> h
 
 -- | Apply a function of eight arguments
-foreign import runFn8 :: forall a b c d e f g h i. Fn8 a b c d e f g h i -> a -> b -> c -> d -> e -> f -> g -> h -> i
+foreign import runFn8
+  :: forall a b c d e f g h i
+   . Fn8 a b c d e f g h i
+  -> a
+  -> b
+  -> c
+  -> d
+  -> e
+  -> f
+  -> g
+  -> h
+  -> i
 
 -- | Apply a function of nine arguments
-foreign import runFn9 :: forall a b c d e f g h i j. Fn9 a b c d e f g h i j -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j
+foreign import runFn9
+  :: forall a b c d e f g h i j
+   . Fn9 a b c d e f g h i j
+  -> a
+  -> b
+  -> c
+  -> d
+  -> e
+  -> f
+  -> g
+  -> h
+  -> i
+  -> j
 
 -- | Apply a function of ten arguments
-foreign import runFn10 :: forall a b c d e f g h i j k. Fn10 a b c d e f g h i j k -> a -> b -> c -> d -> e -> f -> g -> h -> i -> j -> k
+foreign import runFn10
+  :: forall a b c d e f g h i j k
+   . Fn10 a b c d e f g h i j k
+  -> a
+  -> b
+  -> c
+  -> d
+  -> e
+  -> f
+  -> g
+  -> h
+  -> i
+  -> j
+  -> k