Unable to call async method of Arc<Mutex<T: UserData>> with userdata-wrappers feature?

[arkav]

When migrating from version 0.9 I encountered the issue that when I try to call an async method of a Arc<Mutex<T>> of a type that implements UserData for example the following code returns an error.

impl UserData for SharedData {
    fn add_methods<M: mlua::UserDataMethods<Self>>(methods: &mut M) {
        methods.add_async_method("some_async_method", |_, mut this, ()| async move {
            println!("Hello");
            tokio::time::sleep(Duration::from_secs(5)).await;
            println!("from the other side!");
            Ok(())
        });
    }
}

#[tokio::main]
async fn main() -> Result<(), mlua::Error> {
    let lua = Lua::new();

    lua.load(
        r#"
        function test(shared_data)
            shared_data:some_async_method()
        end
    "#,
    )
    .exec()?;

    let shared_data = Arc::new(Mutex::new(SharedData::new()));
    let func: mlua::Function = lua.globals().get("test")?;

    func.call_async::<()>(shared_data).await
}

The error returned:

Error: CallbackError { traceback: "stack traceback:\n\t[C]: in local 'poll'\n\t[string \"?\"]:4: in method 'some_async_method'\n\t[string \"src/main.rs:40:9\"]:3: in function 'test'", cause: BadArgument { to: Some("SharedData.some_async_method"), pos: 1, name: Some("self"), cause: UserDataTypeMismatch } }

Is this intended behavior?

[khvzak]

This is not supported yet.
As a workaround you can change method to:

methods.add_async_function("some_async_method", |_, this: UserDataRef<Arc<Mutex<Self>>>| async move {
    println!("Hello");
    tokio::time::sleep(Duration::from_secs(1)).await;
    println!("from the other side!");
    Ok(())
});

Or receiving AnyUserData and then trying to borrow Self or Arc<Mutex<Self>> to support all cases.

I'll try to fix this in next version, it's not trivial unfortunately.