From 317ce7caa6984b5fda0282308b2e269ece26ae7a Mon Sep 17 00:00:00 2001
From: Alex Orlenko <zxteam@protonmail.com>
Date: Sat, 4 May 2024 21:15:22 +0100
Subject: [PATCH] Add `Lua::set_fflag()` to control Luau feature flags

---
 mlua-sys/src/luau/lua.rs |  5 +++++
 src/lua.rs               | 14 ++++++++++++++
 tests/luau.rs            |  6 ++++++
 3 files changed, 25 insertions(+)

diff --git a/mlua-sys/src/luau/lua.rs b/mlua-sys/src/luau/lua.rs
index 3db6a7b..a2077e1 100644
--- a/mlua-sys/src/luau/lua.rs
+++ b/mlua-sys/src/luau/lua.rs
@@ -553,3 +553,8 @@ pub struct lua_Callbacks {
 extern "C" {
     pub fn lua_callbacks(L: *mut lua_State) -> *mut lua_Callbacks;
 }
+
+// Functions from customization lib
+extern "C" {
+    pub fn luau_setfflag(name: *const c_char, value: c_int) -> c_int;
+}
diff --git a/src/lua.rs b/src/lua.rs
index 35bdf4b..6def0c0 100644
--- a/src/lua.rs
+++ b/src/lua.rs
@@ -1288,6 +1288,20 @@ impl Lua {
         unsafe { (*self.extra.get()).enable_jit = enable };
     }
 
+    /// Sets Luau feature flag (global setting).
+    ///
+    /// See https://github.com/luau-lang/luau/blob/master/CONTRIBUTING.md#feature-flags for details.
+    #[cfg(feature = "luau")]
+    #[doc(hidden)]
+    pub fn set_fflag(name: &str, enabled: bool) -> StdResult<(), ()> {
+        if let Ok(name) = CString::new(name) {
+            if unsafe { ffi::luau_setfflag(name.as_ptr(), enabled as c_int) != 0 } {
+                return Ok(());
+            }
+        }
+        Err(())
+    }
+
     /// Returns Lua source code as a `Chunk` builder type.
     ///
     /// In order to actually compile or run the resulting code, you must call [`Chunk::exec`] or
diff --git a/tests/luau.rs b/tests/luau.rs
index aedcc53..29af6cf 100644
--- a/tests/luau.rs
+++ b/tests/luau.rs
@@ -484,3 +484,9 @@ fn test_buffer() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn test_fflags() {
+    // We cannot really on any particular feature flag to be present
+    assert!(Lua::set_fflag("UnknownFlag", true).is_err());
+}