rework complex enum field conversion

newsfragments/4694.fixed.md

@@ -0,0 +1 @@
+Complex enums now allow field types that either implement `IntoPyObject` by reference or by value together with `Clone`. This makes `Py<T>` available as field type. 

pyo3-macros-backend/src/pyclass.rs

@@ -1233,9 +1233,16 @@ fn impl_complex_enum_struct_variant_cls(
             complex_enum_variant_field_getter(&variant_cls_type, field_name, field.span, ctx)?;
 
         let field_getter_impl = quote! {
-            fn #field_name(slf: #pyo3_path::PyRef<Self>) -> #pyo3_path::PyResult<#field_type> {
+            fn #field_name(slf: #pyo3_path::PyRef<Self>) -> #pyo3_path::PyResult<#pyo3_path::PyObject> {
+                #[allow(unused_imports)]
+                use #pyo3_path::impl_::pyclass::Probe;
+                let py = slf.py();
                 match &*slf.into_super() {
-                    #enum_name::#variant_ident { #field_name, .. } => ::std::result::Result::Ok(::std::clone::Clone::clone(&#field_name)),
+                    #enum_name::#variant_ident { #field_name, .. } =>
+                        #pyo3_path::impl_::pyclass::ConvertField::<
+                            { #pyo3_path::impl_::pyclass::IsIntoPyObjectRef::<#field_type>::VALUE },
+                            { #pyo3_path::impl_::pyclass::IsIntoPyObject::<#field_type>::VALUE },
+                        >::convert_field::<#field_type>(#field_name, py),
                     _ => ::core::unreachable!("Wrong complex enum variant found in variant wrapper PyClass"),
                 }
             }
@@ -1302,9 +1309,16 @@ fn impl_complex_enum_tuple_variant_field_getters(
             })
             .collect();
         let field_getter_impl: syn::ImplItemFn = parse_quote! {
-            fn #field_name(slf: #pyo3_path::PyRef<Self>) -> #pyo3_path::PyResult<#field_type> {
+            fn #field_name(slf: #pyo3_path::PyRef<Self>) -> #pyo3_path::PyResult<#pyo3_path::PyObject> {
+                #[allow(unused_imports)]
+                use #pyo3_path::impl_::pyclass::Probe;
+                let py = slf.py();
                 match &*slf.into_super() {
-                    #enum_name::#variant_ident ( #(#field_access_tokens), *) => ::std::result::Result::Ok(::std::clone::Clone::clone(&val)),
+                    #enum_name::#variant_ident ( #(#field_access_tokens), *) =>
+                        #pyo3_path::impl_::pyclass::ConvertField::<
+                            { #pyo3_path::impl_::pyclass::IsIntoPyObjectRef::<#field_type>::VALUE },
+                            { #pyo3_path::impl_::pyclass::IsIntoPyObject::<#field_type>::VALUE },
+                        >::convert_field::<#field_type>(val, py),
                     _ => ::core::unreachable!("Wrong complex enum variant found in variant wrapper PyClass"),
                 }
             }

src/impl_/pyclass.rs

@@ -1521,6 +1521,38 @@ fn pyo3_get_value<
     Ok((unsafe { &*value }).clone().into_py(py).into_ptr())
 }
 
+pub struct ConvertField<
+    const IMPLEMENTS_INTOPYOBJECT_REF: bool,
+    const IMPLEMENTS_INTOPYOBJECT: bool,
+>;
+
+impl<const IMPLEMENTS_INTOPYOBJECT: bool> ConvertField<true, IMPLEMENTS_INTOPYOBJECT> {
+    #[inline]
+    pub fn convert_field<'a, 'py, T>(obj: &'a T, py: Python<'py>) -> PyResult<Py<PyAny>>
+    where
+        &'a T: IntoPyObject<'py>,
+    {
+        obj.into_pyobject(py)
+            .map(BoundObject::into_any)
+            .map(BoundObject::unbind)
+            .map_err(Into::into)
+    }
+}
+
+impl<const IMPLEMENTS_INTOPYOBJECT: bool> ConvertField<false, IMPLEMENTS_INTOPYOBJECT> {
+    #[inline]
+    pub fn convert_field<'py, T>(obj: &T, py: Python<'py>) -> PyResult<Py<PyAny>>
+    where
+        T: PyO3GetField<'py>,
+    {
+        obj.clone()
+            .into_pyobject(py)
+            .map(BoundObject::into_any)
+            .map(BoundObject::unbind)
+            .map_err(Into::into)
+    }
+}
+
 /// Marker trait whether a class implemented a custom comparison. Used to
 /// silence deprecation of autogenerated `__richcmp__` for enums.
 pub trait HasCustomRichCmp {}

tests/test_enum.rs

@@ -202,9 +202,10 @@ fn test_renaming_all_enum_variants() {
 }
 
 #[pyclass(module = "custom_module")]
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 enum CustomModuleComplexEnum {
     Variant(),
+    Py(Py<PyAny>),
 }
 
 #[test]