How to call an async function created in Rust from Lua?

[elipp]

Hi,

using the async feature, and having stored the result of create_async_function into globals, how does one call that async function "to exhaustion" from lua?

Currently, I am able to run the Rust function until its first .await point, after which the Lua execution just returns some userdata and stops.

Here's the Rust side

globals.set("async_func", lua.create_async_function(
       |_, (x: i32)| async move {
            println!("hi from async!");
            sleep(Duration::from_millis(1000)).await;
            println!("bye from async!");
            Ok::<mlua::Number, mlua::Error>(0.0)
        })?
)?;

Here's what I've tried on the Lua side:

-- this gives "attempt to yield from outside a coroutine":
local function attempt_1(x)
    return async_func(x)
end

-- this prints "hi from async!" and returns some unknown userdata:
local function attempt_2(x)
    local c = coroutine.wrap(function(v) return async_func(v) end)
    return c(x)
end

-- this one loops forever, always reporting the state as "suspended"
local function attempt_3(x)
    local co = coroutine.create(function(v)
        return async_func(v)
    end)
    local count, errorfree, value = 1, nil, nil
    while coroutine.status(co) ~= 'dead' do
        print('----', count); count = count+1
        errorfree, value = coroutine.resume(co)
        print('E: errorfree, value, status', errorfree, value, coroutine.status(co))
    end
    return value
end

[elipp]

...aaand almost immediately after posting this, I found out from the docs that anything with async functions/coroutines must be called with eval_async or similar. 🤣

After that, even the first variant works as expected.