Replace `ahash` with `rapidhash` by fanninpm · Pull Request #7954 · RustPython/RustPython

fanninpm · 2026-05-23T02:04:49Z

Follow-up to #7800.

Back in 2021, ahash was added to RustPython in #2397 because it was faster than the Rust standard library hash/RandomState.
Since then, hashing technology has evolved to the point where rapidhash beats ahash in both the SMHasher and SMHasher3 test suites.
Additionally, rapidhash has very minimal direct dependencies and is portable across CPU architectures.

cc @coolreader18 @joshuamegnauth54

Summary by CodeRabbit

Chores
- Replaced the workspace hashing dependency with an alternative implementation and updated usages across crates for consistent hashing behavior.
- Adjusted dependency grouping so the previous hash crate is no longer included in the automated grouping/configuration.

$Review Change Stack$

coderabbitai · 2026-05-23T02:04:57Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between fd63103 and 133a66c.

⛔ Files ignored due to path filters (1)

Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (11)

.github/dependabot.yml
Cargo.toml
crates/codegen/Cargo.toml
crates/codegen/src/lib.rs
crates/stdlib/Cargo.toml
crates/stdlib/src/contextvars.rs
crates/vm/Cargo.toml
crates/vm/src/builtins/type.rs
crates/vm/src/intern.rs
crates/vm/src/vm/interpreter.rs
crates/vm/src/vm/mod.rs

💤 Files with no reviewable changes (1)

.github/dependabot.yml

✅ Files skipped from review due to trivial changes (1)

crates/codegen/Cargo.toml

📝 Walkthrough

Walkthrough

This PR replaces the ahash crate with rapidhash across the workspace: workspace dependencies updated, Dependabot pattern removed, and hasher types switched from ahash::RandomState to rapidhash::quality::RandomState in codegen, stdlib, and vm crates.

Changes

Hash Library Migration

Layer / File(s)	Summary
Workspace dependency and Dependabot configuration `Cargo.toml`, `.github/dependabot.yml`	Workspace removes `ahash` and adds `rapidhash = "4.4.1"`; Dependabot `cargo` → `random` group `patterns` no longer includes `"ahash"`.
Codegen crate migration `crates/codegen/Cargo.toml`, `crates/codegen/src/lib.rs`	`crates/codegen` removes `ahash` dep, adds `rapidhash`, and updates `IndexMap`/`IndexSet` aliases to use `rapidhash::quality::RandomState`.
Stdlib crate migration `crates/stdlib/Cargo.toml`, `crates/stdlib/src/contextvars.rs`	`crates/stdlib` swaps `ahash` for `rapidhash` and updates the `Hamt` `IndexMap` hasher to `rapidhash::quality::RandomState`.
VM crate migration `crates/vm/Cargo.toml`, `crates/vm/src/builtins/type.rs`, `crates/vm/src/intern.rs`, `crates/vm/src/vm/mod.rs`, `crates/vm/src/vm/interpreter.rs`	`crates/vm` replaces `ahash` with `rapidhash` and updates `PyAttributes`, `StringPool.inner`, `PyGlobalState.frozen`, and the interpreter `frozen` registry `HashMap` types to `rapidhash::quality::RandomState`.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

RustPython/RustPython#7665: Adds ahash to Dependabot Cargo random group patterns; this PR removes it from the same configuration.

Suggested reviewers

coolreader18
youknowone

"🐰 I hopped through Cargo trees today,
swapped ahash out, made rapidhash play,
maps and sets now hum with speed,
a nimble hop for every need.
⚡🥕"

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely summarizes the main change: replacing the ahash hashing library with rapidhash across the codebase.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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ShaharNaveh

Do we need to adjust dependabot as well?

fanninpm · 2026-05-24T00:05:37Z

Do we need to adjust dependabot as well?

That will be the last commit in the series.

youknowone

👍

$ShaharNaveh$

ShaharNaveh approved these changes May 23, 2026

View reviewed changes

$@fanninpm$

fanninpm marked this pull request as ready for review May 24, 2026 03:46

fanninpm added 5 commits May 24, 2026 10:30

$@fanninpm$

Add rapidhash to list of dependencies

b2fe4b5

$@fanninpm$

Use rapidhash::quality::RandomState in codegen crate

3b71c63

$@fanninpm$

Use rapidhash::quality::RandomState in stdlib crate

3c484f4

$@fanninpm$

Use rapidhash::quality::RandomState in vm crate

c95d581

$@fanninpm$

Remove ahash from lists of dependencies

133a66c

$@fanninpm$

fanninpm force-pushed the replace-ahash-with-rapidhash branch from fd63103 to 133a66c Compare May 24, 2026 14:30

$youknowone$

youknowone approved these changes May 25, 2026

View reviewed changes

$@youknowone$

youknowone merged commit bc3d00e into RustPython:main May 25, 2026
26 checks passed

$@fanninpm$

fanninpm deleted the replace-ahash-with-rapidhash branch May 26, 2026 03:00

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Replace `ahash` with `rapidhash` - #7954

Replace `ahash` with `rapidhash`#7954
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fanninpm:replace-ahash-with-rapidhash

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$@fanninpm$ fanninpm commented May 23, 2026 •

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