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

ever0de

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Summary by CodeRabbit

Bug Fixes
- Improved stability of the tee iterator by preventing concurrent or recursive access, reducing the risk of runtime errors or inconsistent behavior. Users will now receive a clear error if re-entrancy is attempted.

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Walkthrough

The PyItertoolsTeeData struct's values field was changed from a read-write lock to a mutex. The get_item method now uses a try_lock() on the mutex to detect re-entrance, returning a runtime error if the lock is already held, and caches iterator results accordingly.

Changes

File(s)	Change Summary
vm/src/stdlib/itertools.rs	Changed `values` from `PyRwLock<Vec<PyObjectRef>>` to `PyMutex<Vec<PyObjectRef>>` in `PyItertoolsTeeData`. Updated `new` and `get_item` to use mutex locking with `try_lock()` and return error on re-entrance.

Poem

A mutex now guards the tee's bright trail,
No more re-entry to make it fail.
Cached treasures locked tight in a row,
One hop at a time, steady and slow.
🐇🔐🌿

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vm/src/stdlib/itertools.rs (1 hunks)

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vm/src/stdlib/itertools.rs

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youknowone

Thank you!

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

aaf1805

ever0de force-pushed the fix/itertools-tee-reentrancy branch from 93a39b4 to aaf1805 Compare July 10, 2025 06:32

youknowone requested changes Jul 10, 2025

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apply feedback PyRwLock -> PyMutex & remove AtomicCell<bool> lock field

17011c4

youknowone approved these changes Jul 10, 2025

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coderabbitai Bot mentioned this pull request Feb 11, 2026

Update doctest,test_generators from v3.14.2 and fix generator bugs #7067

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