mangle_name for __ prefixed members

youknowone · youknowone · commit 8718dc422c52 · 2025-12-10T21:42:47.000+09:00
diff --git a/crates/vm/src/builtins/type.rs b/crates/vm/src/builtins/type.rs
@@ -1185,25 +1185,27 @@ impl Constructor for PyType {
 
         if let Some(ref slots) = heaptype_slots {
             let mut offset = base_member_count;
+            let class_name = typ.name().to_string();
             for member in slots.as_slice() {
+                // Apply name mangling for private attributes (__x -> _ClassName__x)
+                let mangled_name = mangle_name(&class_name, member.as_str());
                 let member_def = PyMemberDef {
-                    name: member.to_string(),
+                    name: mangled_name.clone(),
                     kind: MemberKind::ObjectEx,
                     getter: MemberGetter::Offset(offset),
                     setter: MemberSetter::Offset(offset),
                     doc: None,
                 };
+                let attr_name = vm.ctx.intern_str(mangled_name.as_str());
                 let member_descriptor: PyRef<PyMemberDescriptor> =
                     vm.ctx.new_pyref(PyMemberDescriptor {
                         common: PyDescriptorOwned {
                             typ: typ.clone(),
-                            name: vm.ctx.intern_str(member.as_str()),
+                            name: attr_name,
                             qualname: PyRwLock::new(None),
                         },
                         member: member_def,
                     });
-
-                let attr_name = vm.ctx.intern_str(member.as_str());
                 // __slots__ attributes always get a member descriptor
                 // (this overrides any inherited attribute from MRO)
                 typ.set_attr(attr_name, member_descriptor.into());
@@ -1793,6 +1795,18 @@ fn best_base<'a>(bases: &'a [PyTypeRef], vm: &VirtualMachine) -> PyResult<&'a Py
     Ok(base.unwrap())
 }
 
+/// Apply Python name mangling for private attributes.
+/// `__x` becomes `_ClassName__x` if inside a class.
+fn mangle_name(class_name: &str, name: &str) -> String {
+    // Only mangle names starting with __ and not ending with __
+    if !name.starts_with("__") || name.ends_with("__") || name.contains('.') {
+        return name.to_string();
+    }
+    // Strip leading underscores from class name
+    let class_name = class_name.trim_start_matches('_');
+    format!("_{}{}", class_name, name)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
