ci: add cache-suffix to isolate sanitizer build cache

[joseph-isaacs]

Summary

• Add cache-suffix input to setup-rust action to allow jobs with different RUSTFLAGS to use separate caches
• Use cache-suffix: "sanitizer" for the sanitizer test job to prevent cache pollution between sanitizer and non-sanitizer builds

Test plan

• Verify CI jobs pass
• Confirm sanitizer job uses separate cache key

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.53%. Comparing base (89b236b) to head (47393b7).
⚠️ Report is 3 commits behind head on develop.

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[joseph-isaacs]

yes, do you have a preferred way to get a prefix?

[0ax1]

@claude review

[claude]

Claude finished @0ax1's task —— View job

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Code Review Complete ✓

I've reviewed this PR and the changes look good! Here's my detailed feedback:

Summary

This PR adds a cache-suffix input to the setup-rust action to isolate caches for builds with different RUSTFLAGS. This is a smart solution to prevent cache pollution between the sanitizer build (which uses special RUSTFLAGS) and normal builds.

What Changed

1. .github/actions/setup-rust/action.yml:

   • Added new optional cache-suffix input with empty string default
   • Modified the shared-key in the rust-cache step to conditionally append the suffix using format('-{0}', inputs.cache-suffix)

2. .github/workflows/ci.yml:

   • Added cache-suffix: "sanitizer" to the sanitizer test job that uses special RUSTFLAGS

Review Feedback

✅ Strengths:

• The implementation correctly addresses the cache pollution issue between sanitizer and non-sanitizer builds
• The conditional suffix syntax ${{ inputs.cache-suffix && format('-{0}', inputs.cache-suffix) || '' }} is idiomatic and clean
• The default empty string ensures backward compatibility for existing jobs
• The suffix is only applied where needed (sanitizer job)
• Good documentation in the input description explaining the purpose

💡 Suggestions:

1. Consider applying to other jobs with special RUSTFLAGS: Looking at the workflow, there are other jobs that might benefit from cache isolation:

   • The rust-coverage job (line 334) has RUSTFLAGS: "-Cinstrument-coverage -A warnings"
   • This could potentially cause cache conflicts with other builds

2. Documentation: Consider adding a comment in the workflow near the sanitizer job explaining why the cache-suffix is needed, for future maintainers. Something like:

   # Use separate cache due to different RUSTFLAGS (sanitizer flags)
   cache-suffix: "sanitizer"

3. Regarding the review comment about prefix: The current implementation uses a suffix approach which is appropriate since:

   • It maintains all the existing cache key components in order
   • The conditional format ensures clean key generation
   • If you wanted a prefix instead, you'd use: ${{ inputs.cache-suffix && format('{0}-', inputs.cache-suffix) || '' }}rust-cache-...
   • However, suffix is more intuitive here since it's an optional modifier to the base key

🎯 Recommendation:
This PR is ready to merge. The implementation is sound and solves the stated problem effectively. The optional suggestions above are minor enhancements that could be addressed in follow-up work if desired.

Overall Assessment: ✅ Approved - Clean, well-scoped change that solves a real problem.

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