__anext__ + experimental-async support #5773
Description
Bug Description
In starting to use experimental-async I noticed that __anext__ isn't allowed to be an async function.
Steps to Reproduce
REPO: https://github.com/jessekrubin/pyo3-anext-repro
copy-pasta-ed some of the experimental-async code to write das test.
use futures::channel::oneshot;
use pyo3::prelude::*;
use std::{sync::atomic::Ordering, thread, time::Duration};
fn handle_windows(test: &str) -> String {
let set_event_loop_policy = r#"
import asyncio, sys
if sys.platform == "win32":
asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
"#;
pyo3::impl_::unindent::unindent(set_event_loop_policy) + &pyo3::impl_::unindent::unindent(test)
}
#[pyfunction]
async fn sleep(seconds: f64) -> usize {
let (tx, rx) = oneshot::channel();
thread::spawn(move || {
thread::sleep(Duration::from_secs_f64(seconds));
tx.send(42).unwrap();
});
rx.await.unwrap()
}
#[pyclass]
struct AsyncRange {
count: std::sync::atomic::AtomicUsize,
max: usize,
}
#[pymethods]
impl AsyncRange {
#[new]
fn new(max: usize) -> Self {
Self {
count: std::sync::atomic::AtomicUsize::new(0),
max,
}
}
fn __aiter__(slf: PyRef<'_, Self>) -> PyRef<'_, Self> {
slf
}
async fn __anext__(&self) -> Option<usize> {
let current = self.count.fetch_add(1, Ordering::SeqCst);
if current < self.max {
// simulate async work
sleep(0.001).await;
Some(current + 1)
} else {
None
}
}
}
#[test]
fn async_anext() {
Python::attach(|py| {
let test = r#"
async def main():
results = [value async for value in AsyncRange(3)]
assert results == [1, 2, 3]
asyncio.run(main())
"#;
let globals = pyo3::types::PyDict::new(py);
globals
.set_item("AsyncRange", py.get_type::<AsyncRange>())
.unwrap();
py.run(
&std::ffi::CString::new(pyo3::impl_::unindent::unindent(&handle_windows(test))).unwrap(),
Some(&globals),
None,
)
.unwrap();
});
}Backtrace
jesse@puter[[pyo3-async-anext]]$ cargo test
Compiling pyo3-build-config v0.28.0
Compiling pyo3-macros-backend v0.28.0
Compiling pyo3-ffi v0.28.0
Compiling pyo3 v0.28.0
Compiling pyo3-macros v0.28.0
Compiling repro v0.1.0 (/home/jesse/pyo3-async-anext)
error[E0277]: the trait bound `impl futures::Future<Output = Option<usize>>: IntoPyCallbackOutput<'_, _>` is not satisfied
--> src/main.rs:30:1
|
30 | #[pymethods]
| ^^^^^^^^^^^^ the trait `IntoPyCallbackOutput<'_, _>` is not implemented for `impl futures::Future<Output = Option<usize>>`
|
= help: the following other types implement trait `IntoPyCallbackOutput<'py, Target>`:
`()` implements `IntoPyCallbackOutput<'_, ()>`
`()` implements `IntoPyCallbackOutput<'_, i32>`
`*mut PyObject` implements `IntoPyCallbackOutput<'_, *mut PyObject>`
`HashCallbackOutput` implements `IntoPyCallbackOutput<'_, isize>`
`Result<T, E>` implements `IntoPyCallbackOutput<'py, U>`
`bool` implements `IntoPyCallbackOutput<'_, bool>`
`bool` implements `IntoPyCallbackOutput<'_, i32>`
`usize` implements `IntoPyCallbackOutput<'_, isize>`
`usize` implements `IntoPyCallbackOutput<'_, usize>`
note: required by a bound in `AsyncIterBaseTag::convert`
--> /home/jesse/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/pyo3-0.28.0/src/impl_/pymethods.rs:559:16
|
557 | pub fn convert<'py, Value, Target>(self, py: Python<'py>, value: Value) -> PyResult<Target>
| ------- required by a bound in this associated function
558 | where
559 | Value: IntoPyCallbackOutput<'py, Target>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `AsyncIterBaseTag::convert`
= note: this error originates in the attribute macro `pymethods` (in Nightly builds, run with -Z macro-backtrace for more info)
For more information about this error, try `rustc --explain E0277`.
error: could not compile `repro` (bin "repro" test) due to 1 previous errorYour operating system and version
windows11/rhel8
Your Python version (python --version)
python313
Your Rust version (rustc --version)
1.92.0
Your PyO3 version
0.28.0
How did you install python? Did you use a virtualenv?
uv
Additional Info
No response