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Fix __build_class__ compatibility #6308

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Merged
youknowone merged 2 commits into from
Nov 29, 2025
Merged

Fix __build_class__ compatibility #6308

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94a1903
Update __build_class__
youknowone Nov 29, 2025
cf3e257
fix test
youknowone Nov 29, 2025
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2 changes: 0 additions & 2 deletions Lib/test/test_descr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -479,8 +479,6 @@ def __getitem__(self, i):
self.assertEqual(a[2], 102)
self.assertEqual(a[100:200], (100,200))

# TODO: RUSTPYTHON
@unittest.expectedFailure
def test_metaclass(self):
# Testing metaclasses...
class C(metaclass=type):
Expand Down
4 changes: 0 additions & 4 deletions Lib/test/test_super.py
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Expand Up @@ -162,8 +162,6 @@ def f():

self.assertIs(test_class, A)

# TODO: RUSTPYTHON
@unittest.expectedFailure
def test___class___delayed(self):
# See issue #23722
test_namespace = None
Expand Down Expand Up @@ -236,8 +234,6 @@ def f(self):
with self.assertRaises(AttributeError):
WithClassRef.__classcell__

# TODO: RUSTPYTHON
@unittest.expectedFailure
def test___classcell___missing(self):
# See issue #23722
# Some metaclasses may not pass the original namespace to type.__new__
Expand Down
54 changes: 35 additions & 19 deletions crates/vm/src/stdlib/builtins.rs
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Expand Up @@ -892,13 +892,12 @@ mod builtins {
#[pyfunction]
pub fn __build_class__(
function: PyRef<PyFunction>,
qualified_name: PyStrRef,
name: PyStrRef,
bases: PosArgs,
mut kwargs: KwArgs,
vm: &VirtualMachine,
) -> PyResult {
let name = qualified_name.as_str().split('.').next_back().unwrap();
let name_obj = vm.ctx.new_str(name);
let name_obj: PyObjectRef = name.clone().into();

// Update bases.
let mut new_bases: Option<Vec<PyObjectRef>> = None;
Expand Down Expand Up @@ -942,20 +941,33 @@ mod builtins {
.downcast_exact::<PyType>(vm)
.map(|m| m.into_pyref())
})
.unwrap_or_else(|| Ok(vm.ctx.types.type_type.to_owned()));
.unwrap_or_else(|| {
// if there are no bases, use type; else get the type of the first base
Ok(if bases.is_empty() {
vm.ctx.types.type_type.to_owned()
} else {
bases.first().unwrap().class().to_owned()
})
});

let (metaclass, meta_name) = match metaclass {
Ok(mut metaclass) => {
for base in bases.iter() {
let base_class = base.class();
// if winner is subtype of tmptype, continue (winner is more derived)
if metaclass.fast_issubclass(base_class) {
continue;
}
// if tmptype is subtype of winner, update (tmptype is more derived)
if base_class.fast_issubclass(&metaclass) {
metaclass = base.class().to_owned();
} else if !metaclass.fast_issubclass(base_class) {
return Err(vm.new_type_error(
"metaclass conflict: the metaclass of a derived class must be a (non-strict) \
subclass of the metaclasses of all its bases",
));
metaclass = base_class.to_owned();
continue;
}
// Metaclass conflict
return Err(vm.new_type_error(
"metaclass conflict: the metaclass of a derived class must be a (non-strict) \
subclass of the metaclasses of all its bases",
));
}
let meta_name = metaclass.slot_name();
(metaclass.to_owned().into(), meta_name.to_owned())
Expand All @@ -969,8 +981,7 @@ mod builtins {
let namespace = vm
.get_attribute_opt(metaclass.clone(), identifier!(vm, __prepare__))?
.map_or(Ok(vm.ctx.new_dict().into()), |prepare| {
let args =
FuncArgs::new(vec![name_obj.clone().into(), bases.clone()], kwargs.clone());
let args = FuncArgs::new(vec![name_obj.clone(), bases.clone()], kwargs.clone());
prepare.call(args, vm)
})?;

Expand Down Expand Up @@ -1013,7 +1024,7 @@ mod builtins {
.del_item(vm.ctx.intern_str(".type_params"), vm)
.ok();

let args = FuncArgs::new(vec![name_obj.into(), bases, namespace.into()], kwargs);
let args = FuncArgs::new(vec![name_obj, bases, namespace.into()], kwargs);
let class = metaclass.call(args, vm)?;

// For PEP 695 classes, set __type_params__ on the class from the function
Expand All @@ -1028,16 +1039,21 @@ mod builtins {
class.set_attr(identifier!(vm, __parameters__), type_params, vm)?;
}

if let Some(ref classcell) = classcell {
let classcell = classcell.get().ok_or_else(|| {
vm.new_type_error(format!(
"__class__ not set defining {meta_name:?} as {class:?}. Was __classcell__ propagated to type.__new__?"
// only check cell if cls is a type and cell is a cell object
if let Some(ref classcell) = classcell
&& class.fast_isinstance(vm.ctx.types.type_type)
{
let cell_value = classcell.get().ok_or_else(|| {
vm.new_runtime_error(format!(
"__class__ not set defining {:?} as {:?}. Was __classcell__ propagated to type.__new__?",
name, class
))
})?;

if !classcell.is(&class) {
if !cell_value.is(&class) {
return Err(vm.new_type_error(format!(
"__class__ set to {classcell:?} defining {meta_name:?} as {class:?}"
"__class__ set to {:?} defining {:?} as {:?}",
cell_value, name, class
)));
}
}
Expand Down
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