Rust Toolchain Bump

Stable Rust Toolchain Bump (google-cloud-rust)

This skill automates checking for new stable minor compiler releases from the Rust project (released every 6 weeks), verifying workspace clippy lints, and synchronizing compiler version definitions across CI configurations.

[!NOTE] Bumping the Minimum Supported Rust Version (MSRV) is managed independently under the 1-year policy.

Step 1: Run Toolchain Check Script

Run the automated toolchain check script (requires network access / BypassSandbox: true):

./scripts/check-rust-toolchain.sh

The script will:

1. Extract CURRENT_RUST_VERSION deterministically from .github/workflows/rust-toolchain-check.yaml.
2. Compare against the latest stable release in RELEASES.md.
3. Check out a feature branch (chore-bump-rust-toolchain-1.XX) based on main.
4. Update the local stable compiler (rustup update stable).
5. Attempt to automatically apply machine-applicable clippy suggestions (cargo clippy --fix ...).
6. Check if generated code (**/generated/**) was modified, failing early if action in librarian is required.
7. Run strict workspace clippy verification (cargo clippy --all-features --all-targets --profile=test --workspace -- --deny warnings).
8. Run cargo semver-checks on google-cloud-wkt.

Step 2: Handle Diagnostics & Generated Code Changes

Check git status to inspect any changes made by automatic clippy fixes:

• If check-rust-toolchain.sh exits successfully and ONLY handwritten crates (src/auth, src/gax, src/storage, etc.) were modified:

  • Proceed directly to Step 3. These fixes will be included in the toolchain upgrade PR.

• [CRITICAL] If check-rust-toolchain.sh fails because cargo clippy --fix modified generated code (**/generated/**):

  • Do NOT manually commit edits to generated files.
  • Inspect the diff to see what needs to be updated in the code generator:

    git diff -- '**/generated/**'
    

  • A separate PR is required first: File an issue / PR in googleapis/librarian to update generator templates.
  • Discard local edits in generated directories before committing:

    git restore -- '**/generated/**'
    

  • Once the generator is updated and librarian regenerates the code in google-cloud-rust, resume the toolchain upgrade.

• If check-rust-toolchain.sh fails on remaining warnings in handwritten crates:

  • Fix code diagnostics directly in the working branch, then re-run ./scripts/check-rust-toolchain.sh until clean.

• If semver-checks fails with unsupported rustdoc format vXX:

  • Bump cargo-semver-checks to the latest version in both .gcb/scripts/semver-checks.sh and librarian.yaml, then re-run.

Step 3: Update CI Configuration Files

[!NOTE] The list of CI configuration files below may change over time as new workflows or build steps are added. Always search the repository for the old compiler version number to ensure all references are found.

Search for all occurrences of the old compiler version across the repository (escape the dot, e.g. 1\.97):

git grep -n "1\.XX"

You can also search for key configuration variables:

git grep -n "_RUST_VERSION"
git grep -n "CURRENT_RUST_VERSION"
git grep -n "GHA_RUST_VERSIONS"

[!WARNING] Do NOT modify MSRV configurations: .gcb/msrv.yaml or Cargo.toml (rust-version). Those track the MSRV, which is managed independently under the 1-year policy.

Common files to update include:

1. GitHub Actions Workflows:

   • .github/workflows/sdk.yaml (GHA_RUST_VERSIONS: '{ "rust:current": "1.XX" }')
   • .github/workflows/rust-toolchain-check.yaml (CURRENT_RUST_VERSION: '1.XX')

2. Google Cloud Build Configurations: Update all _RUST_VERSION: '1.XX' entries across .gcb/ and src/**/.gcb/ (excluding msrv.yaml):

   • .gcb/format.yaml
   • .gcb/complex.yaml
   • .gcb/cryptoproviders.yaml
   • .gcb/coverage.yaml
   • .gcb/integration.yaml
   • src/auth/.gcb/integration.yaml

Step 4: Validate and Prepare PR

1. Verify formatting and check builds:

   cargo fmt --check
   cargo check --workspace --all-targets
   

2. Commit all changes following CONTRIBUTING.md#commit-messages:

   git commit -am "chore(ci): update Rust toolchain to 1.XX" -m "Update stable compiler version to 1.XX across GitHub Actions and Google Cloud Build configurations."