Add SHA3 private attribute parity to hashlib hash objects by moreal · Pull Request #7134 · RustPython/RustPython

Walkthrough

This PR introduces Keccak-related helper functions and constants to the hashlib module, then exposes Keccak metadata properties (capacity bits, rate bits, suffix byte) on PyHasher and PyHasherXof classes.

Changes

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• Make HASH/HASHXOF types immutable #7131: Modifies the same PyHasher and PyHasherXof types to change pyclass flags to IMMUTABLETYPE.

Suggested reviewers

• youknowone

Poem

🐰 A hasher's delight, so crisp and clean,
Keccak secrets now are seen,
Capacity, rate, and suffix too—
Python's metadata dreams come true! ✨

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

• 📝 Generate docstrings

crates/stdlib/src/hashlib.rs (2)

157-181: Properties are correct; consider .ok_or_else() for conciseness.

Minor style nit: the match + Some/None pattern could be slightly more concise with .ok_or_else().

fn _capacity_bits(&self, vm: &VirtualMachine) -> PyResult<usize> {
    let block_size = self.ctx.read().block_size();
    keccak_capacity_bits(&self.name, block_size)
        .ok_or_else(|| vm.new_attribute_error(format!("'HASH' object has no attribute '_capacity_bits'")))
}

This is purely stylistic — the current form is clear too.

---

256-280: Duplicated property bodies between PyHasher and PyHasherXof.

These three properties are identical to their PyHasher counterparts (lines 157–181), differing only in the "HASHXOF" vs "HASH" class name string. Given the #[pyclass] macro constraints, full dedup is awkward, but you could extract thin helpers that accept the class name:

♻️ Example dedup

fn get_capacity_bits(name: &str, block_size: usize, class_name: &str, vm: &VirtualMachine) -> PyResult<usize> {
    keccak_capacity_bits(name, block_size)
        .ok_or_else(|| vm.new_attribute_error(format!("'{class_name}' object has no attribute '_capacity_bits'")))
}

fn get_rate_bits(name: &str, block_size: usize, class_name: &str, vm: &VirtualMachine) -> PyResult<usize> {
    keccak_rate_bits(name, block_size)
        .ok_or_else(|| vm.new_attribute_error(format!("'{class_name}' object has no attribute '_rate_bits'")))
}

fn get_suffix(name: &str, class_name: &str, vm: &VirtualMachine) -> PyResult<PyBytes> {
    keccak_suffix(name)
        .map(|s| vec![s].into())
        .ok_or_else(|| vm.new_attribute_error(format!("'{class_name}' object has no attribute '_suffix'")))
}

Then each #[pygetset] becomes a one-liner delegating to the shared helper.

As per coding guidelines, "When branches differ only in a value but share common logic, extract the differing value first, then call the common logic once to avoid duplicate code."

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