ci: one coverage tool, not two, and stop building them from source

Merged
RM
2mo ago
+18-28

User description

What

CI measured the same workspace's coverage twice, with two different tools, and threw one result away.

security.yml carried a coverage job that installed cargo-tarpaulin, produced coverage/cobertura.xml, and uploaded it via actions/upload-artifact. Nothing downloaded that artifact — not another job, not Codecov, not a status check.

rust.yml's test (ubuntu-latest) job already runs cargo llvm-cov over the same --workspace and reports lcov to Codecov. That is the coverage signal the repository actually consumes.

Evidence

jobtime on PR #144output consumed?
security.ymlcode coverage (tarpaulin)3m36s❌ artifact, never downloaded
rust.ymltest (ubuntu-latest) (llvm-cov)1m23s✅ uploaded to Codecov

The discarded job was the slowest thing in CI, and most of its runtime was cargo install cargo-tarpaulin compiling from crates.io. Its Swatinem/rust-cache step could not help — it ran after the install, and caches the workspace target dir rather than ~/.cargo/bin.

Changes

  • security.yml: remove the coverage job. A header comment records why, so it does not get re-added.
  • rust.yml: install cargo-llvm-cov via taiki-e/install-action with fallback: none instead of cargo install. This matches how the cargo audit job in security.yml already installs its tool — same action, same pinned SHA, same refusal to silently fall back to a source build.

Safety

  • No coverage reporting is lost. The lcov upload to Codecov is untouched; only the unconsumed second measurement goes.
  • Dropping the code coverage check name blocks nothing — verified main carries no branch protection (GET /repos/rmems/writ/branches/main/protection → 404 "Branch not protected"), so there are no required status checks to satisfy.
  • actionlint clean on all four workflows.

Not in scope

The Codecov gate itself is vacuous (target: 0, threshold: 0.0) and release.yml is dead — both tracked separately.

Refs #1

🤖 Generated with Claude Code

https://claude.ai/code/session_016yFLnKN9zQA7uzgpYxTrjX

Summary by cubic

Stops CI from running two coverage tools on the same workspace: removes the coverage job from security.yml that measured with cargo-tarpaulin and uploaded an artifact nobody consumed. The existing cargo llvm-cov coverage in rust.yml remains the single source of truth. Also installs cargo-llvm-cov via a prebuilt binary instead of compiling from source, matching how cargo audit is installed.

CodeAnt-AI Description

Streamline CI coverage checks and reduce unnecessary build time

What Changed

  • Removed the unused duplicate coverage job and its unconsumed report artifact
  • Kept workspace coverage testing and Codecov reporting in the existing Rust test job
  • Installs the coverage tool from a prebuilt release instead of compiling it during each CI run

Impact

✅ Faster pull request checks
✅ Fewer redundant CI jobs
✅ Coverage reports remain available in Codecov

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