Also replace IterANextOutput by autoref-based specialization to allow returning arbitrary values

pyo3-macros-backend/src/pymethod.rs

@@ -799,8 +799,9 @@ const __NEXT__: SlotDef = SlotDef::new("Py_tp_iternext", "iternextfunc")
     );
 const __AWAIT__: SlotDef = SlotDef::new("Py_am_await", "unaryfunc");
 const __AITER__: SlotDef = SlotDef::new("Py_am_aiter", "unaryfunc");
-const __ANEXT__: SlotDef = SlotDef::new("Py_am_anext", "unaryfunc").return_conversion(
-    TokenGenerator(|| quote! { _pyo3::class::pyasync::IterANextOutput::<_, _> }),
+const __ANEXT__: SlotDef = SlotDef::new("Py_am_anext", "unaryfunc").return_specialized_conversion(
+    TokenGenerator(|| quote! { AsyncIterBaseKind, AsyncIterOptionKind, AsyncIterResultOptionKind }),
+    TokenGenerator(|| quote! { async_iter_tag }),
 );
 const __LEN__: SlotDef = SlotDef::new("Py_mp_length", "lenfunc").ret_ty(Ty::PySsizeT);
 const __CONTAINS__: SlotDef = SlotDef::new("Py_sq_contains", "objobjproc")

src/impl_/pymethods.rs

@@ -1,4 +1,5 @@
 use crate::callback::IntoPyCallbackOutput;
+use crate::exceptions::PyStopAsyncIteration;
 use crate::gil::LockGIL;
 use crate::impl_::panic::PanicTrap;
 use crate::internal_tricks::extract_c_string;
@@ -381,3 +382,83 @@ pub trait IterResultOptionKind {
 }
 
 impl<Value> IterResultOptionKind for PyResult<Option<Value>> {}
+
+// Autoref-based specialization for handling `__anext__` returning `Option`
+
+pub struct AsyncIterBaseTag;
+
+impl AsyncIterBaseTag {
+    #[inline]
+    pub fn convert<Value, Target>(self, py: Python<'_>, value: Value) -> PyResult<Target>
+    where
+        Value: IntoPyCallbackOutput<Target>,
+    {
+        value.convert(py)
+    }
+}
+
+pub trait AsyncIterBaseKind {
+    #[inline]
+    fn async_iter_tag(&self) -> AsyncIterBaseTag {
+        AsyncIterBaseTag
+    }
+}
+
+impl<Value> AsyncIterBaseKind for &Value {}
+
+pub struct AsyncIterOptionTag;
+
+impl AsyncIterOptionTag {
+    #[inline]
+    pub fn convert<Value>(
+        self,
+        py: Python<'_>,
+        value: Option<Value>,
+    ) -> PyResult<*mut ffi::PyObject>
+    where
+        Value: IntoPyCallbackOutput<*mut ffi::PyObject>,
+    {
+        match value {
+            Some(value) => value.convert(py),
+            None => Err(PyStopAsyncIteration::new_err(())),
+        }
+    }
+}
+
+pub trait AsyncIterOptionKind {
+    #[inline]
+    fn async_iter_tag(&self) -> AsyncIterOptionTag {
+        AsyncIterOptionTag
+    }
+}
+
+impl<Value> AsyncIterOptionKind for Option<Value> {}
+
+pub struct AsyncIterResultOptionTag;
+
+impl AsyncIterResultOptionTag {
+    #[inline]
+    pub fn convert<Value>(
+        self,
+        py: Python<'_>,
+        value: PyResult<Option<Value>>,
+    ) -> PyResult<*mut ffi::PyObject>
+    where
+        Value: IntoPyCallbackOutput<*mut ffi::PyObject>,
+    {
+        match value {
+            Ok(Some(value)) => value.convert(py),
+            Ok(None) => Err(PyStopAsyncIteration::new_err(())),
+            Err(err) => Err(err),
+        }
+    }
+}
+
+pub trait AsyncIterResultOptionKind {
+    #[inline]
+    fn async_iter_tag(&self) -> AsyncIterResultOptionTag {
+        AsyncIterResultOptionTag
+    }
+}
+
+impl<Value> AsyncIterResultOptionKind for PyResult<Option<Value>> {}

src/lib.rs

@@ -351,6 +351,7 @@ pub mod class {
     /// For compatibility reasons this has not yet been removed, however will be done so
     /// once <https://github.com/rust-lang/rust/issues/30827> is resolved.
     pub mod pyasync {
+        #[allow(deprecated)]
         pub use crate::pyclass::{IterANextOutput, PyIterANextOutput};
     }
 

src/pyclass.rs

@@ -155,6 +155,10 @@ where
 /// Output of `__anext__`.
 ///
 /// <https://docs.python.org/3/reference/expressions.html#agen.__anext__>
+#[deprecated(
+    since = "0.21.0",
+    note = "Use `Option` or `PyStopAsyncIteration` instead."
+)]
 pub enum IterANextOutput<T, U> {
     /// An expression which the generator yielded.
     Yield(T),
@@ -163,40 +167,25 @@ pub enum IterANextOutput<T, U> {
 }
 
 /// An [IterANextOutput] of Python objects.
+#[deprecated(
+    since = "0.21.0",
+    note = "Use `Option` or `PyStopAsyncIteration` instead."
+)]
+#[allow(deprecated)]
 pub type PyIterANextOutput = IterANextOutput<PyObject, PyObject>;
 
-impl IntoPyCallbackOutput<*mut ffi::PyObject> for PyIterANextOutput {
-    fn convert(self, _py: Python<'_>) -> PyResult<*mut ffi::PyObject> {
-        match self {
-            IterANextOutput::Yield(o) => Ok(o.into_ptr()),
-            IterANextOutput::Return(opt) => {
-                Err(crate::exceptions::PyStopAsyncIteration::new_err((opt,)))
-            }
-        }
-    }
-}
-
-impl<T, U> IntoPyCallbackOutput<PyIterANextOutput> for IterANextOutput<T, U>
+#[allow(deprecated)]
+impl<T, U> IntoPyCallbackOutput<*mut ffi::PyObject> for IterANextOutput<T, U>
 where
     T: IntoPy<PyObject>,
     U: IntoPy<PyObject>,
 {
-    fn convert(self, py: Python<'_>) -> PyResult<PyIterANextOutput> {
+    fn convert(self, py: Python<'_>) -> PyResult<*mut ffi::PyObject> {
         match self {
-            IterANextOutput::Yield(o) => Ok(IterANextOutput::Yield(o.into_py(py))),
-            IterANextOutput::Return(o) => Ok(IterANextOutput::Return(o.into_py(py))),
-        }
-    }
-}
-
-impl<T> IntoPyCallbackOutput<PyIterANextOutput> for Option<T>
-where
-    T: IntoPy<PyObject>,
-{
-    fn convert(self, py: Python<'_>) -> PyResult<PyIterANextOutput> {
-        match self {
-            Some(o) => Ok(PyIterANextOutput::Yield(o.into_py(py))),
-            None => Ok(PyIterANextOutput::Return(py.None().into())),
+            IterANextOutput::Yield(o) => Ok(o.into_py(py).into_ptr()),
+            IterANextOutput::Return(o) => Err(crate::exceptions::PyStopAsyncIteration::new_err(
+                o.into_py(py),
+            )),
         }
     }
 }