macros: Support #[pyo3(name)] on enum variants

CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Allow `#[classattr]` take `Python` argument. [#2383](https://github.com/PyO3/pyo3/issues/2383)
 - Add `CompareOp::matches` to easily implement `__richcmp__` as the result of a
   Rust `std::cmp::Ordering` comparison. [#2460](https://github.com/PyO3/pyo3/pull/2460)
+- Supprt `#[pyo3(name)]` on enum variants [#2457](https://github.com/PyO3/pyo3/pull/2457)
 
 ### Changed
 

pyo3-macros-backend/src/pyclass.rs

@@ -330,7 +330,17 @@ fn impl_class(
 
 struct PyClassEnumVariant<'a> {
     ident: &'a syn::Ident,
-    /* currently have no more options */
+    options: EnumVariantPyO3Options,
+}
+
+impl<'a> PyClassEnumVariant<'a> {
+    fn python_name(&self) -> Cow<'_, syn::Ident> {
+        self.options
+            .name
+            .as_ref()
+            .map(|name_attr| Cow::Borrowed(&name_attr.value.0))
+            .unwrap_or_else(|| Cow::Owned(self.ident.unraw()))
+    }
 }
 
 struct PyClassEnum<'a> {
@@ -342,7 +352,7 @@ struct PyClassEnum<'a> {
 }
 
 impl<'a> PyClassEnum<'a> {
-    fn new(enum_: &'a syn::ItemEnum) -> syn::Result<Self> {
+    fn new(enum_: &'a mut syn::ItemEnum) -> syn::Result<Self> {
         fn is_numeric_type(t: &syn::Ident) -> bool {
             [
                 "u8", "i8", "u16", "i16", "u32", "i32", "u64", "i64", "u128", "i128", "usize",
@@ -370,7 +380,7 @@ impl<'a> PyClassEnum<'a> {
 
         let variants = enum_
             .variants
-            .iter()
+            .iter_mut()
             .map(extract_variant_data)
             .collect::<syn::Result<_>>()?;
         Ok(Self {
@@ -407,6 +417,46 @@ pub fn build_py_enum(
     Ok(impl_enum(enum_, &args, doc, method_type))
 }
 
+/// `#[pyo3()]` options for pyclass enum variants
+struct EnumVariantPyO3Options {
+    name: Option<NameAttribute>,
+}
+
+enum EnumVariantPyO3Option {
+    Name(NameAttribute),
+}
+
+impl Parse for EnumVariantPyO3Option {
+    fn parse(input: ParseStream<'_>) -> Result<Self> {
+        let lookahead = input.lookahead1();
+        if lookahead.peek(attributes::kw::name) {
+            input.parse().map(EnumVariantPyO3Option::Name)
+        } else {
+            Err(lookahead.error())
+        }
+    }
+}
+
+impl EnumVariantPyO3Options {
+    fn take_pyo3_options(attrs: &mut Vec<syn::Attribute>) -> Result<Self> {
+        let mut options = EnumVariantPyO3Options { name: None };
+
+        for option in take_pyo3_options(attrs)? {
+            match option {
+                EnumVariantPyO3Option::Name(name) => {
+                    ensure_spanned!(
+                        options.name.is_none(),
+                        name.span() => "`name` may only be specified once"
+                    );
+                    options.name = Some(name);
+                }
+            }
+        }
+
+        Ok(options)
+    }
+}
+
 fn impl_enum(
     enum_: PyClassEnum<'_>,
     args: &PyClassArgs,
@@ -433,7 +483,11 @@ fn impl_enum_class(
         let variants_repr = variants.iter().map(|variant| {
             let variant_name = variant.ident;
             // Assuming all variants are unit variants because they are the only type we support.
-            let repr = format!("{}.{}", get_class_python_name(cls, args), variant_name);
+            let repr = format!(
+                "{}.{}",
+                get_class_python_name(cls, args),
+                variant.python_name(),
+            );
             quote! { #cls::#variant_name => #repr, }
         });
         let mut repr_impl: syn::ImplItemMethod = syn::parse_quote! {
@@ -511,7 +565,7 @@ fn impl_enum_class(
         cls,
         args,
         methods_type,
-        enum_default_methods(cls, variants.iter().map(|v| v.ident)),
+        enum_default_methods(cls, variants.iter().map(|v| (v.ident, v.python_name()))),
         default_slots,
     )
     .doc(doc)
@@ -557,33 +611,34 @@ fn generate_default_protocol_slot(
 
 fn enum_default_methods<'a>(
     cls: &'a syn::Ident,
-    unit_variant_names: impl IntoIterator<Item = &'a syn::Ident>,
+    unit_variant_names: impl IntoIterator<Item = (&'a syn::Ident, Cow<'a, syn::Ident>)>,
 ) -> Vec<MethodAndMethodDef> {
     let cls_type = syn::parse_quote!(#cls);
-    let variant_to_attribute = |ident: &syn::Ident| ConstSpec {
+    let variant_to_attribute = |var_ident: &syn::Ident, py_ident: &syn::Ident| ConstSpec {
-        rust_ident: ident.clone(),
+        rust_ident: var_ident.clone(),
         attributes: ConstAttributes {
             is_class_attr: true,
             name: Some(NameAttribute {
                 kw: syn::parse_quote! { name },
-                value: NameLitStr(ident.clone()),
+                value: NameLitStr(py_ident.clone()),
             }),
             deprecations: Default::default(),
         },
     };
     unit_variant_names
         .into_iter()
-        .map(|var| gen_py_const(&cls_type, &variant_to_attribute(var)))
+        .map(|(var, py_name)| gen_py_const(&cls_type, &variant_to_attribute(var, &py_name)))
         .collect()
 }
 
-fn extract_variant_data(variant: &syn::Variant) -> syn::Result<PyClassEnumVariant<'_>> {
+fn extract_variant_data(variant: &mut syn::Variant) -> syn::Result<PyClassEnumVariant<'_>> {
     use syn::Fields;
     let ident = match variant.fields {
         Fields::Unit => &variant.ident,
         _ => bail_spanned!(variant.span() => "Currently only support unit variants."),
     };
-    Ok(PyClassEnumVariant { ident })
+    let options = EnumVariantPyO3Options::take_pyo3_options(&mut variant.attrs)?;
+    Ok(PyClassEnumVariant { ident, options })
 }
 
 fn descriptors_to_items(

tests/test_enum.rs

@@ -175,3 +175,18 @@ fn test_rename_enum_repr_correct() {
         py_assert!(py, var1, "repr(var1) == 'MyEnum.Variant'");
     })
 }
+
+#[pyclass]
+#[derive(Debug, PartialEq, Clone)]
+pub enum RenameVariantEnum {
+    #[pyo3(name = "VARIANT")]
+    Variant,
+}
+
+#[test]
+fn test_rename_variant_repr_correct() {
+    Python::with_gil(|py| {
+        let var1 = Py::new(py, RenameVariantEnum::Variant).unwrap();
+        py_assert!(py, var1, "repr(var1) == 'RenameVariantEnum.VARIANT'");
+    })
+}