bazelbuild/bazel

rules_rust crash under bazel 9

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#29114 opened on Mar 26, 2026

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P2help wantedteam-ExternalDepstype: bug

Description

Description of the bug:

https://github.com/patrickmscott/rules_rust_bazel9

When modifying Cargo.toml and requesting CARGO_BAZEL_REPIN=true, bazel crashes because the lockfile has been modified.

@katre

Which category does this issue belong to?

Rules API

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

https://github.com/patrickmscott/rules_rust_bazel9

Which operating system are you running Bazel on?

linux

What is the output of bazel info release?

release 9.0.1

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

No response

Contributor guide

Tech stack
rust
Domain
build systemapi
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Familiarity with BazelUnderstanding of rules rustRust programming language
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the crash using the provided reproduction repository at https://github.com/patrickmscott/rules rust bazel9. The bug occurs when modifying Cargo.toml and setting CARGO BAZEL REPIN=true. Look at the Bazel source code related to rules rust lockfile handling, particularly the interaction between Cargo.toml changes and lockfile regeneration. Check for any recent changes in Bazel 9 that might have altered this behavior. The issue has no linked PRs, but there is a mention of @katre who may provide more context.