fix __qualname__ for complex enum variants (#5796)

* fix `__qualname__` for complex enum variants

* newsfragment

* clippy

Author: davidhewitt

newsfragments/5796.fixed.md

@@ -0,0 +1 @@
+Fix `__qualname__` for complex `#[pyclass]` enum variants to include the enum name.

pyo3-macros-backend/src/pyclass.rs

@@ -1452,6 +1452,11 @@ fn impl_complex_enum_struct_variant_cls(
         field_getter_impls.push(field_getter_impl);
     }
 
+    let (qualname, qualname_impl) =
+        impl_complex_enum_variant_qualname(enum_name, variant_ident, &variant_cls_type, ctx)?;
+
+    field_getters.push(qualname);
+
     let (variant_match_args, match_args_const_impl) =
         impl_complex_enum_variant_match_args(ctx, &variant_cls_type, &field_names)?;
 
@@ -1469,6 +1474,8 @@ fn impl_complex_enum_struct_variant_cls(
 
             #match_args_const_impl
 
+            #qualname_impl
+
             #(#field_getter_impls)*
         }
     };
@@ -1641,6 +1648,11 @@ fn impl_complex_enum_tuple_variant_cls(
         &mut field_types,
     )?;
 
+    let (qualname, qualname_impl) =
+        impl_complex_enum_variant_qualname(enum_name, variant_ident, &variant_cls_type, ctx)?;
+
+    field_getters.push(qualname);
+
     let num_fields = variant.fields.len();
 
     let (variant_len, len_method_impl) =
@@ -1674,6 +1686,8 @@ fn impl_complex_enum_tuple_variant_cls(
 
             #match_args_method_impl
 
+            #qualname_impl
+
             #(#field_getter_impls)*
         }
     };
@@ -1685,6 +1699,34 @@ fn gen_complex_enum_variant_class_ident(enum_: &Ident, variant: &Ident) -> Ident
     format_ident!("{}_{}", enum_, variant)
 }
 
+fn impl_complex_enum_variant_qualname(
+    enum_name: &syn::Ident,
+    variant_ident: &syn::Ident,
+    variant_cls_type: &syn::Type,
+    ctx: &Ctx,
+) -> syn::Result<(MethodAndMethodDef, syn::ImplItemFn)> {
+    let Ctx { pyo3_path, .. } = ctx;
+    let qualname = format!("{}.{}", enum_name, variant_ident);
+    let mut qualname_impl: syn::ImplItemFn = {
+        parse_quote! {
+            #[classattr]
+            fn __qualname__(py: #pyo3_path::Python<'_>) -> &'static str {
+                #qualname
+            }
+        }
+    };
+
+    let spec = FnSpec::parse(
+        &mut qualname_impl.sig,
+        &mut qualname_impl.attrs,
+        Default::default(),
+    )?;
+
+    // NB: Deliberately add no introspection here, this is __qualname__
+    let qualname = impl_py_class_attribute(variant_cls_type, &spec, ctx)?;
+    Ok((qualname, qualname_impl))
+}
+
 #[cfg(feature = "experimental-inspect")]
 struct FunctionIntrospectionData<'a> {
     names: &'a [&'a str],

tests/test_enum.rs

@@ -404,3 +404,18 @@ fn complex_enum_with_raw_pattern_match() {
         "#);
     });
 }
+
+#[test]
+fn complex_enum_variant_qualname() {
+    #[pyclass(skip_from_py_object)]
+    pub enum ComplexEnum {
+        A(i32),
+        B { msg: String },
+    }
+
+    Python::attach(|py| {
+        let cls = py.get_type::<ComplexEnum>();
+        py_assert!(py, cls, "cls.A.__qualname__ == 'ComplexEnum.A'");
+        py_assert!(py, cls, "cls.B.__qualname__ == 'ComplexEnum.B'");
+    });
+}