From 53b7b5b70bbb640609e23f3cfb91d62739f3c806 Mon Sep 17 00:00:00 2001
From: Alex Orlenko <zxteam@protonmail.com>
Date: Sun, 27 Aug 2023 23:01:37 +0100
Subject: [PATCH] Fix setting userdata (static) fields when it has __index
 metamethod/function. Closes #312

---
 src/lua.rs        |  1 +
 tests/userdata.rs | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/lua.rs b/src/lua.rs
index 57fb304..11765ce 100644
--- a/src/lua.rs
+++ b/src/lua.rs
@@ -2667,6 +2667,7 @@ impl Lua {
                     rawset_field(state, metatable_index, "__index")?;
                 }
                 _ => {
+                    ffi::lua_pop(state, 1);
                     // Propagate fields to the field getters
                     for (k, f) in registry.fields {
                         registry.field_getters.push((k, f))
diff --git a/tests/userdata.rs b/tests/userdata.rs
index 98431bd..da6c40d 100644
--- a/tests/userdata.rs
+++ b/tests/userdata.rs
@@ -506,6 +506,9 @@ fn test_functions() -> Result<()> {
 
 #[test]
 fn test_fields() -> Result<()> {
+    let lua = Lua::new();
+    let globals = lua.globals();
+
     #[derive(Copy, Clone)]
     struct MyUserData(i64);
 
@@ -533,8 +536,6 @@ fn test_fields() -> Result<()> {
         }
     }
 
-    let lua = Lua::new();
-    let globals = lua.globals();
     globals.set("ud", MyUserData(7))?;
     lua.load(
         r#"
@@ -555,6 +556,33 @@ fn test_fields() -> Result<()> {
     )
     .exec()?;
 
+    // Case: fields + __index metamethod (function)
+    struct MyUserData2(i64);
+
+    impl UserData for MyUserData2 {
+        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+            fields.add_field("z", 0);
+            fields.add_field_method_get("x", |_, data| Ok(data.0));
+        }
+
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_meta_method(MetaMethod::Index, |_, _, name: StdString| match &*name {
+                "y" => Ok(Some(-1)),
+                _ => Ok(None),
+            });
+        }
+    }
+
+    globals.set("ud", MyUserData2(1))?;
+    lua.load(
+        r#"
+        assert(ud.x == 1)
+        assert(ud.y == -1)
+        assert(ud.z == 0)
+    "#,
+    )
+    .exec()?;
+
     Ok(())
 }