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fix(itertools): add re-entrancy guard to tee object #5931

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

fix(itertools): add re-entrancy guard to tee object #5931

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aaf1805
fix(itertools): add re-entrancy guard to tee object
ever0de Jul 10, 2025
17011c4
apply feedback PyRwLock -> PyMutex & remove AtomicCell<bool> lock field
ever0de Jul 10, 2025
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2 changes: 0 additions & 2 deletions Lib/test/test_itertools.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1761,8 +1761,6 @@ def test_tee_del_backward(self):
del forward, backward
raise

# TODO: RUSTPYTHON
@unittest.expectedFailure
def test_tee_reenter(self):
class I:
first = True
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17 changes: 11 additions & 6 deletions vm/src/stdlib/itertools.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1184,23 +1184,28 @@ mod decl {
#[derive(Debug)]
struct PyItertoolsTeeData {
iterable: PyIter,
values: PyRwLock<Vec<PyObjectRef>>,
values: PyMutex<Vec<PyObjectRef>>,
}

impl PyItertoolsTeeData {
fn new(iterable: PyIter, _vm: &VirtualMachine) -> PyResult<PyRc<Self>> {
Ok(PyRc::new(Self {
iterable,
values: PyRwLock::new(vec![]),
values: PyMutex::new(vec![]),
}))
}

fn get_item(&self, vm: &VirtualMachine, index: usize) -> PyResult<PyIterReturn> {
if self.values.read().len() == index {
let result = raise_if_stop!(self.iterable.next(vm)?);
self.values.write().push(result);
let Some(mut values) = self.values.try_lock() else {
return Err(vm.new_runtime_error("cannot re-enter the tee iterator"));
};

if values.len() == index {
let obj = raise_if_stop!(self.iterable.next(vm)?);
values.push(obj);
}
Ok(PyIterReturn::Return(self.values.read()[index].clone()))

Ok(PyIterReturn::Return(values[index].clone()))
}
}

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