From e30b42522433b31523eb929c1ac37bfbaf07ebfc Mon Sep 17 00:00:00 2001
From: Alex Orlenko <zxteam@protonmail.com>
Date: Sat, 27 Jan 2024 11:51:59 +0000
Subject: [PATCH] Fix crash when initializing Luau sandbox without stdlibs
 (#361)

---
 mlua-sys/src/luau/lauxlib.rs |  9 ++++++---
 tests/luau.rs                | 16 ++++++++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/mlua-sys/src/luau/lauxlib.rs b/mlua-sys/src/luau/lauxlib.rs
index 73788af..9f4384c 100644
--- a/mlua-sys/src/luau/lauxlib.rs
+++ b/mlua-sys/src/luau/lauxlib.rs
@@ -144,9 +144,12 @@ pub unsafe fn luaL_sandbox(L: *mut lua_State, enabled: c_int) {
 
     // set all builtin metatables to read-only
     lua_pushliteral(L, "");
-    lua_getmetatable(L, -1);
-    lua_setreadonly(L, -1, enabled);
-    lua_pop(L, 2);
+    if lua_getmetatable(L, -1) != 0 {
+        lua_setreadonly(L, -1, enabled);
+        lua_pop(L, 2);
+    } else {
+        lua_pop(L, 1);
+    }
 
     // set globals to readonly and activate safeenv since the env is immutable
     lua_setreadonly(L, LUA_GLOBALSINDEX, enabled);
diff --git a/tests/luau.rs b/tests/luau.rs
index 987ea4f..aedcc53 100644
--- a/tests/luau.rs
+++ b/tests/luau.rs
@@ -275,6 +275,22 @@ fn test_sandbox() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_sandbox_nolibs() -> Result<()> {
+    let lua = Lua::new_with(StdLib::NONE, LuaOptions::default()).unwrap();
+
+    lua.sandbox(true)?;
+    lua.load("global = 123").exec()?;
+    let n: i32 = lua.load("return global").eval()?;
+    assert_eq!(n, 123);
+    assert_eq!(lua.globals().get::<_, Option<i32>>("global")?, Some(123));
+
+    lua.sandbox(false)?;
+    assert_eq!(lua.globals().get::<_, Option<i32>>("global")?, None);
+
+    Ok(())
+}
+
 #[test]
 fn test_sandbox_threads() -> Result<()> {
     let lua = Lua::new();