reject SemLock reduce by youknowone · Pull Request #6738 · RustPython/RustPython

youknowone

📝 Walkthrough

Walkthrough

A new __reduce__ method is added to the SemLock class in the multiprocessing module. This method raises a TypeError to prevent direct pickling of SemLock objects, requiring users to use the appropriate multiprocessing.SemLock wrapper for serialization support instead.

Changes

Cohort / File(s)	Summary
SemLock pickling restriction `crates/stdlib/src/multiprocessing.rs`	Added `__reduce__` method to `SemLock` class that raises `TypeError` with message "cannot pickle 'SemLock' object" to block direct serialization

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

RustPython/RustPython#6542: Modifies the core SemLock implementation in multiprocessing module; this PR complements it by adding pickle prevention via the __reduce__ method.

Poem

🐰 A lock that cannot be pickled sweet,
No brines nor jars shall make it neat,
For SemLock stays locked away,
Wrap it well, the proper way! 🔒

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'reject SemLock reduce' directly and specifically describes the main change: preventing SemLock objects from being pickled by implementing a reduce method that rejects serialization.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

📝 Generate docstrings

📜 Recent review details

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Review profile: CHILL

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📥 Commits

Reviewing files that changed from the base of the PR and between 609dbb1 and 5697ab3.

⛔ Files ignored due to path filters (1)

Lib/test/test_concurrent_futures/test_process_pool.py is excluded by !Lib/**

📒 Files selected for processing (1)

crates/stdlib/src/multiprocessing.rs

🧰 Additional context used

📓 Path-based instructions (1)

**/*.rs

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

**/*.rs: Follow the default rustfmt code style using cargo fmt to format Rust code
Always run clippy to lint code (cargo clippy) before completing tasks and fix any warnings or lints introduced by changes
Follow Rust best practices for error handling and memory management
Use the macro system (pyclass, pymodule, pyfunction, etc.) when implementing Python functionality in Rust

Files:

crates/stdlib/src/multiprocessing.rs

🔇 Additional comments (1)

crates/stdlib/src/multiprocessing.rs (1)

550-555: LGTM!

The __reduce__ method correctly prevents direct pickling of SemLock objects by raising a TypeError. This is consistent with CPython's behavior and the existing _rebuild classmethod design pattern—the higher-level multiprocessing.synchronize.SemLock wrapper is expected to handle serialization while using _rebuild for reconstruction.

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