rust-lang / rust-lang/rust

Seedable hashmap for testing?

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#128,948 2 comments 0 reactions 0 assignees View on GitHub

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C-feature-request T-libs
Dominant language
Rust
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Description

This is inspired by the many regressions in https://github.com/rust-lang/rust/issues/128899 that appeared to be "sorting" issues but actually seem to be hashmap issues. It would be nice if we had some way, even if only for unstable/nightly/internal/literally-just-crater usage, to tweak std's hashmap (or just the RNG for it?) so that we could determine if the hashmap's iteration order is the reason a crate's tests are failing.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading the regressions in rust-lang/rust#128899 and the surrounding discussion here. Investigate how std's hashmap iteration order and RNG are controlled, and consider the constraints of an unstable, nightly, internal, or crater-only mechanism; done means a concrete, testable way to vary hashmap behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
testing-qa
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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