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__slots__ xor __dict__ , name mangling by youknowone · Pull Request #6392 · RustPython/RustPython · GitHub
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__slots__ xor __dict__ , name mangling #6392

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Merged
youknowone merged 2 commits into from
Dec 10, 2025
Merged

__slots__ xor __dict__ , name mangling #6392

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f893da6
__slots__ xor __dict__
youknowone Dec 10, 2025
8718dc4
mangle_name for `__` prefixed members
youknowone Dec 10, 2025
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mangle_name for __ prefixed members
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@youknowone
youknowone committed Dec 10, 2025
commit 8718dc422c52b12cedafa6147b3ecbcda696d1ad
22 changes: 18 additions & 4 deletions crates/vm/src/builtins/type.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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());
Expand Down Expand Up @@ -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::*;
Expand Down
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