Unraw complex struct enum field python names (#5050)

* Unraw complex struct enum field python names

Stray case related to #2395 (probably unnoticed because the functionality is
newer and a bit of an edge case).

The `python_name` of struct-type enum variant fields (and the `__match_args__`
of the variant) do not unraw the names of these fields, which effectively
makes them unusable as the resulting identifiers contain '#' which the Python
lexer interprets as comments. The only reason you'd probably want to do this
anyway is to use reserved identifiers (`type` in my case).

* Add newsfragment for fix

* Fix clippy lints in impl_complex_enum_variant_match_args and callers

No need to pass mutable vec ref anymore

* don't overeagerly collect field_names iterator

* add test case for complex enums containing raw identifiers

* only test raw ident pattern matching on Python 3.10+

Author: hgmich

newsfragments/5050.fixed.md

@@ -0,0 +1 @@
+Fix struct-type complex enum variant fields exposing raw identifiers as `r#ident` in Python bindings.

pyo3-macros-backend/src/pyclass.rs

@@ -1188,15 +1188,16 @@ fn impl_complex_enum_variant_cls(
 fn impl_complex_enum_variant_match_args(
     ctx @ Ctx { pyo3_path, .. }: &Ctx,
     variant_cls_type: &syn::Type,
-    field_names: &mut Vec<Ident>,
+    field_names: &[Ident],
 ) -> syn::Result<(MethodAndMethodDef, syn::ImplItemFn)> {
     let ident = format_ident!("__match_args__");
+    let field_names_unraw = field_names.iter().map(|name| name.unraw());
     let mut match_args_impl: syn::ImplItemFn = {
         parse_quote! {
             #[classattr]
             fn #ident(py: #pyo3_path::Python<'_>) -> #pyo3_path::PyResult<#pyo3_path::Bound<'_, #pyo3_path::types::PyTuple>> {
                 #pyo3_path::types::PyTuple::new::<&str, _>(py, [
-                    #(stringify!(#field_names),)*
+                    #(stringify!(#field_names_unraw),)*
                 ])
             }
         }
@@ -1257,7 +1258,7 @@ fn impl_complex_enum_struct_variant_cls(
     }
 
     let (variant_match_args, match_args_const_impl) =
-        impl_complex_enum_variant_match_args(ctx, &variant_cls_type, &mut field_names)?;
+        impl_complex_enum_variant_match_args(ctx, &variant_cls_type, &field_names)?;
 
     field_getters.push(variant_match_args);
 
@@ -1432,7 +1433,7 @@ fn impl_complex_enum_tuple_variant_cls(
     slots.push(variant_getitem);
 
     let (variant_match_args, match_args_method_impl) =
-        impl_complex_enum_variant_match_args(ctx, &variant_cls_type, &mut field_names)?;
+        impl_complex_enum_variant_match_args(ctx, &variant_cls_type, &field_names)?;
 
     field_getters.push(variant_match_args);
 
@@ -1743,7 +1744,7 @@ fn complex_enum_variant_field_getter<'a>(
     let spec = FnSpec {
         tp: crate::method::FnType::Getter(self_type.clone()),
         name: field_name,
-        python_name: field_name.clone(),
+        python_name: field_name.unraw(),
         signature,
         convention: crate::method::CallingConvention::Noargs,
         text_signature: None,

tests/test_enum.rs

@@ -369,3 +369,38 @@ fn custom_eq() {
         assert!(b.as_any().ne("A").unwrap());
     })
 }
+
+#[pyclass]
+#[derive(Clone, Copy)]
+pub enum ComplexEnumWithRaw {
+    Raw { r#type: i32 },
+}
+
+// Cover simple field lookups with raw identifiers
+#[test]
+fn complex_enum_with_raw() {
+    Python::with_gil(|py| {
+        let complex = ComplexEnumWithRaw::Raw { r#type: 314159 };
+
+        py_assert!(py, complex, "complex.type == 314159");
+    });
+}
+
+// Cover pattern matching with raw identifiers
+#[test]
+#[cfg(Py_3_10)]
+fn complex_enum_with_raw_pattern_match() {
+    Python::with_gil(|py| {
+        let complex = ComplexEnumWithRaw::Raw { r#type: 314159 };
+        let cls = py.get_type::<ComplexEnumWithRaw>();
+
+        // Cover destructuring by pattern matching
+        py_run!(py, cls complex, r#"
+        match complex:
+            case cls.Raw(type=ty):
+                assert ty == 314159
+            case _:
+                assert False, "no matching variant found"
+        "#);
+    });
+}