fix error with complex enums with many fields (PyO3#4832)

newsfragments/4832.fixed.md

@@ -0,0 +1 @@
+`#[pyclass]` complex enums support more than 12 variant fields.

pyo3-macros-backend/src/pyclass.rs

@@ -19,8 +19,9 @@ use crate::method::{FnArg, FnSpec, PyArg, RegularArg};
 use crate::pyfunction::ConstructorAttribute;
 use crate::pyimpl::{gen_py_const, get_cfg_attributes, PyClassMethodsType};
 use crate::pymethod::{
-    impl_py_getter_def, impl_py_setter_def, MethodAndMethodDef, MethodAndSlotDef, PropertyType,
-    SlotDef, __GETITEM__, __HASH__, __INT__, __LEN__, __REPR__, __RICHCMP__, __STR__,
+    impl_py_class_attribute, impl_py_getter_def, impl_py_setter_def, MethodAndMethodDef,
+    MethodAndSlotDef, PropertyType, SlotDef, __GETITEM__, __HASH__, __INT__, __LEN__, __REPR__,
+    __RICHCMP__, __STR__,
 };
 use crate::pyversions::is_abi3_before;
 use crate::utils::{self, apply_renaming_rule, Ctx, LitCStr, PythonDoc};
@@ -1185,34 +1186,30 @@ fn impl_complex_enum_variant_cls(
 }
 
 fn impl_complex_enum_variant_match_args(
-    ctx: &Ctx,
+    ctx @ Ctx { pyo3_path, .. }: &Ctx,
     variant_cls_type: &syn::Type,
     field_names: &mut Vec<Ident>,
-) -> (MethodAndMethodDef, syn::ImplItemConst) {
+) -> syn::Result<(MethodAndMethodDef, syn::ImplItemFn)> {
     let ident = format_ident!("__match_args__");
-    let match_args_const_impl: syn::ImplItemConst = {
-        let args_tp = field_names.iter().map(|_| {
-            quote! { &'static str }
-        });
+    let mut match_args_impl: syn::ImplItemFn = {
         parse_quote! {
-            #[allow(non_upper_case_globals)]
-            const #ident: ( #(#args_tp,)* ) = (
-                #(stringify!(#field_names),)*
-            );
+            #[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),)*
+                ])
+            }
         }
     };
 
-    let spec = ConstSpec {
-        rust_ident: ident,
-        attributes: ConstAttributes {
-            is_class_attr: true,
-            name: None,
-        },
-    };
-
-    let variant_match_args = gen_py_const(variant_cls_type, &spec, ctx);
+    let spec = FnSpec::parse(
+        &mut match_args_impl.sig,
+        &mut match_args_impl.attrs,
+        Default::default(),
+    )?;
+    let variant_match_args = impl_py_class_attribute(variant_cls_type, &spec, ctx)?;
 
-    (variant_match_args, match_args_const_impl)
+    Ok((variant_match_args, match_args_impl))
 }
 
 fn impl_complex_enum_struct_variant_cls(
@@ -1260,14 +1257,15 @@ 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, &mut field_names)?;
 
     field_getters.push(variant_match_args);
 
     let cls_impl = quote! {
         #[doc(hidden)]
         #[allow(non_snake_case)]
         impl #variant_cls {
+            #[allow(clippy::too_many_arguments)]
             fn __pymethod_constructor__(py: #pyo3_path::Python<'_>, #(#fields_with_types,)*) -> #pyo3_path::PyClassInitializer<#variant_cls> {
                 let base_value = #enum_name::#variant_ident { #(#field_names,)* };
                 <#pyo3_path::PyClassInitializer<#enum_name> as ::std::convert::From<#enum_name>>::from(base_value).add_subclass(#variant_cls)
@@ -1434,14 +1432,15 @@ 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, &mut field_names)?;
 
     field_getters.push(variant_match_args);
 
     let cls_impl = quote! {
         #[doc(hidden)]
         #[allow(non_snake_case)]
         impl #variant_cls {
+            #[allow(clippy::too_many_arguments)]
             fn __pymethod_constructor__(py: #pyo3_path::Python<'_>, #(#field_names : #field_types,)*) -> #pyo3_path::PyClassInitializer<#variant_cls> {
                 let base_value = #enum_name::#variant_ident ( #(#field_names,)* );
                 <#pyo3_path::PyClassInitializer<#enum_name> as ::std::convert::From<#enum_name>>::from(base_value).add_subclass(#variant_cls)

pyo3-macros-backend/src/pymethod.rs

@@ -526,7 +526,7 @@ fn impl_clear_slot(cls: &syn::Type, spec: &FnSpec<'_>, ctx: &Ctx) -> syn::Result
     })
 }
 
-fn impl_py_class_attribute(
+pub(crate) fn impl_py_class_attribute(
     cls: &syn::Type,
     spec: &FnSpec<'_>,
     ctx: &Ctx,

src/tests/hygiene/pyclass.rs

@@ -92,6 +92,44 @@ pub enum TupleEnumEqOrd {
     Variant2(u32),
 }
 
+#[crate::pyclass(crate = "crate")]
+pub enum ComplexEnumManyVariantFields {
+    ManyStructFields {
+        field_1: u16,
+        field_2: u32,
+        field_3: u32,
+        field_4: i32,
+        field_5: u32,
+        field_6: u32,
+        field_7: u8,
+        field_8: u32,
+        field_9: i32,
+        field_10: u32,
+        field_11: u32,
+        field_12: u32,
+        field_13: u32,
+        field_14: i16,
+        field_15: u32,
+    },
+    ManyTupleFields(
+        u16,
+        u32,
+        u32,
+        i32,
+        u32,
+        u32,
+        u8,
+        u32,
+        i32,
+        u32,
+        u32,
+        u32,
+        u32,
+        i16,
+        u32,
+    ),
+}
+
 #[crate::pyclass(str = "{x}, {y}, {z}")]
 #[pyo3(crate = "crate")]
 pub struct PointFmt {