How to implement asynchronous __anext__ method in new pyo3 version (0.21.0)

[chandr-andr]

Hello! Thanks for the new version of Pyo3, It's awesome.

I want to understand how to implement the asynchronous __anext__ method now.

In your documentation https://pyo3.rs/main/migration.html#iteranextoutput-are-deprecated, you show an example with anext but there is no example with really asynchronous code.

Let's assume I need to write something like this:

#[pyclass]
struct RequestMaker {
	url: String
}

#[pymethods]
impl RequestMaker {
    fn __aiter__(slf: Py<Self>) -> Py<Self> {
        slf
    }

    async fn __anext__(&self) -> Option<String> {
        let response: Option<String> = make_request(self.url).await?;
        if let Some(response) = response {
            Some(response)
	}
		
        None
    }
}

As I understand __anext__ method doesn't support async construct and the docs said that it must return Python awaitable, but __await__ or __iter__ methods also don't support async.

The question is how can I expose asynchronous code in __anext__ to Python?
As there is no pyo3_asyncio with future_into_py anymore, I'm a bit confused about how to implement such an idea.

let res = pyo3_asyncio::tokio::future_into_py(py, async { future.await.map_err(Into::into) })
        .map(Into::into)?;
Ok(res)

[chandr-andr]

I've found one strange solution. I couldn't install pyo3-asyncio to use the future_into_py function because it depends on pyo3 v0.20.0.
So my solution is to fork pyo3-asyncio library in my repository, change the version of pyo3 to 0.21.1 in Cargo.toml, and build locally.

So, now I can use future_into_py function.

Now it works, but looks a bit complicated.