From e08ff38803b4dbbe820e9b8a98123bc1641d1642 Mon Sep 17 00:00:00 2001
From: luaneko <lumi@lua.re>
Date: Mon, 23 Jun 2025 07:02:50 +1000
Subject: [PATCH] Implement variadic support in luaify

---
 crates/luaify/src/generate.rs | 27 +++++++++++++++++++++++----
 crates/luaify/tests/test.rs   | 18 ++++++++++++++++++
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/crates/luaify/src/generate.rs b/crates/luaify/src/generate.rs
index 0e8bb41..06591e6 100644
--- a/crates/luaify/src/generate.rs
+++ b/crates/luaify/src/generate.rs
@@ -569,9 +569,10 @@ fn generate_expr_while(f: &mut Formatter, whil: &ExprWhile, cx: Context) -> Resu
 }
 
 fn generate_punctuated_expr(f: &mut Formatter, exprs: &Punctuated<Expr, Token![,]>) -> Result<()> {
+    let len = exprs.len();
     for (i, expr) in exprs.iter().enumerate() {
         (i != 0).then(|| f.write(","));
-        generate_expr(f, expr, Context::expr(false))?;
+        generate_expr(f, expr, Context::expr(i == len - 1))?;
     }
     Ok(())
 }
@@ -795,6 +796,7 @@ fn generate_receiver(f: &mut Formatter, recv: &Receiver) -> Result<()> {
 fn generate_macro(f: &mut Formatter, mac: &Macro, cx: Context) -> Result<()> {
     match format!("{}", mac.path.require_ident()?).as_str() {
         "concat" => generate_macro_concat(f, mac, cx),
+        "variadic" => generate_macro_variadic(f, mac, cx),
         "embed" => generate_macro_embed(f, mac, cx),
         "raw" => generate_macro_raw(f, mac, cx),
         name => syn_error!(mac.path, "unknown macro '{name}'"),
@@ -813,6 +815,17 @@ fn generate_macro_concat(f: &mut Formatter, mac: &Macro, cx: Context) -> Result<
     Ok(())
 }
 
+fn generate_macro_variadic(f: &mut Formatter, mac: &Macro, cx: Context) -> Result<()> {
+    syn_assert!(
+        cx.is_multi_expr(),
+        mac,
+        "variadic! must be in multi-value expression position"
+    );
+    cx.is_ret().then(|| f.write("return"));
+    f.write("...");
+    Ok(())
+}
+
 fn generate_macro_embed(f: &mut Formatter, mac: &Macro, cx: Context) -> Result<()> {
     syn_assert!(cx.is_value(), mac, "embed! must be in expression position");
     cx.is_ret().then(|| f.write("return"));
@@ -871,9 +884,9 @@ fn generate_pat_ident(f: &mut Formatter, ident: &PatIdent, _cx: PatContext) -> R
     generate_ident(f, &ident.ident)
 }
 
-fn generate_pat_macro(f: &mut Formatter, mac: &PatMacro, _cx: PatContext) -> Result<()> {
+fn generate_pat_macro(f: &mut Formatter, mac: &PatMacro, cx: PatContext) -> Result<()> {
     assert_no_attrs!(mac);
-    generate_macro(f, &mac.mac, Context::expr(false))
+    generate_macro(f, &mac.mac, Context::expr(cx.is_multi()))
 }
 
 fn generate_pat_tuple(f: &mut Formatter, tuple: &PatTuple, cx: PatContext) -> Result<()> {
@@ -900,9 +913,15 @@ fn generate_pat_wild(f: &mut Formatter, wild: &PatWild, _cx: PatContext) -> Resu
 }
 
 fn generate_punctuated_pat(f: &mut Formatter, pats: &Punctuated<Pat, Token![,]>) -> Result<()> {
+    let len = pats.len();
     for (i, pat) in pats.iter().enumerate() {
         (i != 0).then(|| f.write(","));
-        generate_pat(f, pat, PatContext::Single)?;
+        let cx = if i == len - 1 {
+            PatContext::Multi
+        } else {
+            PatContext::Single
+        };
+        generate_pat(f, pat, cx)?;
     }
     Ok(())
 }
diff --git a/crates/luaify/tests/test.rs b/crates/luaify/tests/test.rs
index 36eb7fd..7119167 100644
--- a/crates/luaify/tests/test.rs
+++ b/crates/luaify/tests/test.rs
@@ -373,3 +373,21 @@ fn ifs() {
         r#"function()if a==b then c();elseif b==c then return a();else d();end;end"#
     );
 }
+
+#[test]
+fn variadic() {
+    assert_eq!(luaify!(|a, b, variadic!()| {}), r#"function(a,b,...)end"#);
+    assert_eq!(
+        luaify!(|variadic!()| {
+            let (a, b) = variadic!();
+        }),
+        r#"function(...)local a,b=...;end"#
+    );
+    assert_eq!(
+        luaify!(|a, variadic!()| {
+            let (a, b) = (a, b, c, variadic!());
+            func(a, b, (c, (d, variadic!())))
+        }),
+        r#"function(a,...)local a,b=a,b,c,...;return func(a,b,c,d,...);end"#
+    );
+}