Async methods now takes Receiver

pyo3-derive-backend/src/defs.rs

@@ -156,18 +156,21 @@ pub const ASYNC: Proto = Proto {
     slot_table: "pyo3::ffi::PyAsyncMethods",
     set_slot_table: "set_async_methods",
     methods: &[
-        MethodProto::Unary {
+        MethodProto::UnaryS {
             name: "__await__",
+            arg: "Receiver",
             pyres: true,
             proto: "pyo3::class::pyasync::PyAsyncAwaitProtocol",
         },
-        MethodProto::Unary {
+        MethodProto::UnaryS {
             name: "__aiter__",
+            arg: "Receiver",
             pyres: true,
             proto: "pyo3::class::pyasync::PyAsyncAiterProtocol",
         },
-        MethodProto::Unary {
+        MethodProto::UnaryS {
             name: "__anext__",
+            arg: "Receiver",
             pyres: true,
             proto: "pyo3::class::pyasync::PyAsyncAnextProtocol",
         },

src/class/macros.rs

@@ -34,8 +34,9 @@ macro_rules! py_unarys_func {
         {
             $crate::callback_body!(py, {
                 let slf = py.from_borrowed_ptr::<$crate::PyCell<T>>(slf);
-                let borrow = <T::Receiver>::try_from_pycell(slf)
-                    .map_err(|e| e.into())?;
+                let borrow =
+                    <T::Receiver as $crate::derive_utils::TryFromPyCell<_>>::try_from_pycell(slf)
+                        .map_err(|e| e.into())?;
 
                 $class::$f(borrow).into()$(.map($conv))?
             })

src/class/pyasync.rs

@@ -8,6 +8,7 @@
 //! [PEP-0492](https://www.python.org/dev/peps/pep-0492/)
 //!
 
+use crate::derive_utils::TryFromPyCell;
 use crate::err::PyResult;
 use crate::{ffi, PyClass, PyObject};
 
@@ -16,21 +17,21 @@ use crate::{ffi, PyClass, PyObject};
 /// Each method in this trait corresponds to Python async/await implementation.
 #[allow(unused_variables)]
 pub trait PyAsyncProtocol<'p>: PyClass {
-    fn __await__(&'p self) -> Self::Result
+    fn __await__(slf: Self::Receiver) -> Self::Result
     where
         Self: PyAsyncAwaitProtocol<'p>,
     {
         unimplemented!()
     }
 
-    fn __aiter__(&'p self) -> Self::Result
+    fn __aiter__(slf: Self::Receiver) -> Self::Result
     where
         Self: PyAsyncAiterProtocol<'p>,
     {
         unimplemented!()
     }
 
-    fn __anext__(&'p mut self) -> Self::Result
+    fn __anext__(slf: Self::Receiver) -> Self::Result
     where
         Self: PyAsyncAnextProtocol<'p>,
     {
@@ -58,16 +59,19 @@ pub trait PyAsyncProtocol<'p>: PyClass {
 }
 
 pub trait PyAsyncAwaitProtocol<'p>: PyAsyncProtocol<'p> {
+    type Receiver: TryFromPyCell<'p, Self>;
     type Success: crate::IntoPy<PyObject>;
     type Result: Into<PyResult<Self::Success>>;
 }
 
 pub trait PyAsyncAiterProtocol<'p>: PyAsyncProtocol<'p> {
+    type Receiver: TryFromPyCell<'p, Self>;
     type Success: crate::IntoPy<PyObject>;
     type Result: Into<PyResult<Self::Success>>;
 }
 
 pub trait PyAsyncAnextProtocol<'p>: PyAsyncProtocol<'p> {
+    type Receiver: TryFromPyCell<'p, Self>;
     type Success: crate::IntoPy<PyObject>;
     type Result: Into<PyResult<Option<Self::Success>>>;
 }
@@ -90,13 +94,13 @@ impl ffi::PyAsyncMethods {
     where
         T: for<'p> PyAsyncAwaitProtocol<'p>,
     {
-        self.am_await = py_unary_func!(PyAsyncAwaitProtocol, T::__await__);
+        self.am_await = py_unarys_func!(PyAsyncAwaitProtocol, T::__await__);
     }
     pub fn set_aiter<T>(&mut self)
     where
         T: for<'p> PyAsyncAiterProtocol<'p>,
     {
-        self.am_aiter = py_unary_func!(PyAsyncAiterProtocol, T::__aiter__);
+        self.am_aiter = py_unarys_func!(PyAsyncAiterProtocol, T::__aiter__);
     }
     pub fn set_anext<T>(&mut self)
     where
@@ -123,7 +127,9 @@ mod anext {
         fn convert(self, py: Python) -> PyResult<*mut ffi::PyObject> {
             match self.0 {
                 Some(val) => Ok(val.into_py(py).into_ptr()),
-                None => Err(crate::exceptions::StopAsyncIteration::py_err(())),
+                None => Err(crate::exceptions::StopAsyncIteration::py_err(
+                    "Task Completed",
+                )),
             }
         }
     }
@@ -133,12 +139,6 @@ mod anext {
     where
         T: for<'p> PyAsyncAnextProtocol<'p>,
     {
-        py_unary_func!(
-            PyAsyncAnextProtocol,
-            T::__anext__,
-            call_mut,
-            *mut crate::ffi::PyObject,
-            IterANextOutput
-        )
+        py_unarys_func!(PyAsyncAnextProtocol, T::__anext__, IterANextOutput)
     }
 }

tests/test_dunder.rs

@@ -1,5 +1,6 @@
 use pyo3::class::{
-    PyContextProtocol, PyIterProtocol, PyMappingProtocol, PyObjectProtocol, PySequenceProtocol,
+    PyAsyncProtocol, PyContextProtocol, PyIterProtocol, PyMappingProtocol, PyObjectProtocol,
+    PySequenceProtocol,
 };
 use pyo3::exceptions::{IndexError, ValueError};
 use pyo3::prelude::*;
@@ -552,3 +553,77 @@ fn getattr_doesnt_override_member() {
     py_assert!(py, inst, "inst.data == 4");
     py_assert!(py, inst, "inst.a == 8");
 }
+
+/// Wraps a Python future and yield it once.
+#[pyclass]
+struct OnceFuture {
+    future: PyObject,
+    polled: bool,
+}
+
+#[pymethods]
+impl OnceFuture {
+    #[new]
+    fn new(future: PyObject) -> Self {
+        OnceFuture {
+            future,
+            polled: false,
+        }
+    }
+}
+
+#[pyproto]
+impl PyAsyncProtocol for OnceFuture {
+    fn __await__(slf: PyRef<Self>) -> PyResult<Py<Self>> {
+        Ok(slf.into())
+    }
+}
+
+#[pyproto]
+impl PyIterProtocol for OnceFuture {
+    fn __iter__(slf: PyRef<Self>) -> PyResult<Py<Self>> {
+        Ok(slf.into())
+    }
+    fn __next__(mut slf: PyRefMut<Self>) -> PyResult<Option<PyObject>> {
+        if !slf.polled {
+            slf.polled = true;
+            Ok(Some(slf.future.clone()))
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+#[test]
+fn test_await() {
+    let gil = Python::acquire_gil();
+    let py = gil.python();
+    let once = py.get_type::<OnceFuture>();
+    let source = pyo3::indoc::indoc!(
+        r#"
+import asyncio
+import sys
+
+async def main():
+    res = await Once(await asyncio.sleep(0.1))
+    return res
+
+# It looks like that https://bugs.python.org/issue38563 solves this problem,
+# but we see still errors on Github actions...
+if sys.platform == "win32" and sys.version_info >= (3, 8, 0):
+    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
+loop = asyncio.get_event_loop()
+assert loop.run_until_complete(main()) is None
+loop.close()
+"#
+    );
+    let globals = PyModule::import(py, "__main__").unwrap().dict();
+    globals.set_item("Once", once).unwrap();
+    py.run(source, None, Some(globals))
+        .map_err(|e| {
+            e.print(py);
+            py.run("import sys; sys.stderr.flush()", None, None)
+                .unwrap();
+        })
+        .unwrap();
+}