[rb] Turn off external caching on portable Ruby

[p0deje]

🔗 Related Issues

💥 What does this PR do?

🔧 Implementation Notes

💡 Additional Considerations

🔄 Types of changes

• Cleanup (formatting, renaming)
• Bug fix (backwards compatible)
• New feature (non-breaking change which adds functionality and tests!)
• Breaking change (fix or feature that would cause existing functionality to change)

[qodo-code-review]

Review Summary by Qodo

Disable external caching for Ruby in Bazel workflow

🐞 Bug fix

Walkthroughs

Description

• Disable external caching for Ruby in Bazel workflow
• Prevents caching issues with portable Ruby builds
• Adds ruby: false to manifest configuration

File Changes

1. .github/workflows/bazel.yml 🐞 Bug fix +1/-0

Disable Ruby external caching in Bazel workflow

• Added ruby: false to the external-cache manifest configuration
• Prevents Bazel from caching Ruby dependencies in portable builds
• Aligns Ruby caching behavior with other pinned extensions

.github/workflows/bazel.yml

---

[qodo-code-review]

Code Review by Qodo

🐞 Bugs (1) 📘 Rule violations (0) 📎 Requirement gaps (0) 🎨 UX Issues (0)

1. Ruby cache disable incomplete 🐞 Bug ☼ Reliability

Description

ruby: false is only added to the inputs.caching Bazel setup, but the inputs.caching == false
setup still passes an external-cache manifest without a ruby entry, so workflows that set
caching: false won’t explicitly disable portable Ruby external caching. This makes the PR’s “turn
off external caching on portable Ruby” behavior dependent on the caching input and may leave
affected jobs unchanged.

Code

.github/workflows/bazel.yml[R169-172]

          external-cache: |
            manifest:
              crates: rust/Cargo.Bazel.lock
+              ruby: false

Evidence

The Bazel workflow has two setup branches: the caching-enabled branch now disables ruby in the
external-cache manifest, but the caching-disabled branch still defines external-cache and does not
include ruby: false. Some workflows (e.g., CI-RBE) call this reusable workflow with `caching:
false and then run bazel test //... and bazel build //...`, which will exercise repos/toolchains
declared by the rules_ruby extension; MODULE.bazel explicitly enables portable_ruby = True and
registers a repo named ruby (the portable Ruby toolchain).

.github/workflows/bazel.yml[158-203]
.github/workflows/ci-rbe.yml[24-34]
scripts/github-actions/ci-build.sh[1-27]
MODULE.bazel[272-284]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
The reusable Bazel workflow disables external caching for the portable Ruby repo only in the `inputs.caching` branch. The `inputs.caching == false` branch still sets `external-cache` without explicitly disabling `ruby`, so callers that run with `caching: false` won’t get the intended portable-Ruby cache disablement.

### Issue Context
Some workflows call `./.github/workflows/bazel.yml` with `caching: false` (e.g., CI-RBE) and still run `bazel test //...` and `bazel build //...`, which can require the rules_ruby portable Ruby toolchain declared in `MODULE.bazel`.

### Fix Focus Areas
- .github/workflows/bazel.yml[192-201]

### Suggested change
Add `ruby: false` under the `external-cache: |\n  manifest:` block in the **"Setup Bazel without caching"** step as well (mirroring the caching-enabled branch).

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[Copilot]

Pull request overview

Updates the GitHub Actions Bazel workflow cache configuration to avoid using the external cache for the portable Ruby toolchain.

Changes:

• Adds a ruby: false entry to the external-cache manifest in .github/workflows/bazel.yml to disable caching for Ruby.