chore: bring back Rust build CI cache

[michael1011]

Effectively reverts a96a976

Found that nice trick in rust-bitcoin/rust-miniscript#880

Summary by CodeRabbit

• Chores
  • Enhanced CI/CD pipeline infrastructure with optimizations to improve build stability and efficiency.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

The CI workflow is enhanced with disk space optimization and Rust build caching. Free disk space maintenance steps remove Android, Dotnet, and Haskell components across multiple jobs. Rust builds now cache Cargo paths and target directories using composite keys derived from OS, Rust version, and Cargo.lock hash.

Changes

Cohort / File(s)	Summary
Disk Space Optimization .github/workflows/ci.yml	Adds endersonmenezes/free-disk-space@v3 action steps to multiple CI jobs with options to remove Android, Dotnet, and Haskell components.
Rust Build Caching .github/workflows/ci.yml	Introduces actions/cache@v4 for Rust builds, caching Cargo-related paths and target directory. Cache keys use composite strategy based on OS, rust-version, and Cargo.lock hash, with restore-key fallbacks.

Sequence Diagram

sequenceDiagram
    participant Job as CI Job
    participant DiskSpace as Free Disk Space
    participant Cache as Rust Cache
    participant RustBuild as Rust Build

    activate Job
    Note over Job: Job starts
    Job->>DiskSpace: Run free-disk-space@v3
    Note over DiskSpace: Remove Android, Dotnet, Haskell
    DiskSpace-->>Job: Disk space freed
    
    Job->>Cache: Restore Rust cache
    Note over Cache: Key: OS + rust-version + Cargo.lock
    Cache-->>Job: Cache hit or miss
    
    Job->>RustBuild: Run Rust build/test
    RustBuild-->>Job: Compilation completes
    
    Job->>Cache: Save Rust cache
    Cache-->>Job: Cache updated
    
    deactivate Job
    Note over Job: Job complete

Loading

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Consistency verification: Ensure free-disk-space and cache steps are applied uniformly across all target jobs with no gaps
• Cache key correctness: Verify that composite keys (OS + rust-version + Cargo.lock) are consistently formatted and correctly reference the hash algorithm
• Restore-key fallback logic: Confirm that restore-key patterns provide appropriate cache hits without being too greedy

Poem

🐰 Disk clears and caches bloom,
Our CI escapes the storage gloom!
Rust builds zip with wings so fleet,
Android, Dotnet—no more heat,
Swift compilation—what a treat! ⚡

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: restoring Rust build caching in CI workflows, which aligns with the summary showing Rust build caching additions via actions/cache.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch ci-cache

---

📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 22f861f and 183febe.

📒 Files selected for processing (1)

• .github/workflows/ci.yml (4 hunks)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

• GitHub Check: build (ubuntu-latest, 20, stable)
• GitHub Check: build-rust (ubuntu-latest, 20, stable)
• GitHub Check: build (ubuntu-latest, 20, stable)

🔇 Additional comments (4)

.github/workflows/ci.yml (4)

16-21: Free disk space optimization is appropriate.

The placement before checkout ensures maximum disk availability for the build process. Removing unused components aligns with CI best practices.

---

50-63: Cache configuration follows Rust best practices, but verify key differentiation is intentional.

The cache paths are comprehensive and match official recommendations. However, the key prefix npm-rust-build differs from the build-rust job's cargo-build (line 141), preventing cache sharing between jobs.

Is this intentional, given that the first job runs npm run compile (line 69) while the second runs direct cargo build (line 150)?

---

93-98: LGTM.

Consistent with the free disk space optimization in the build job.

---

131-144: Rust build cache configuration is correct.

The cache key prefix cargo-build is appropriately distinct from the build job's npm-rust-build, reflecting the difference between npm-driven and direct cargo builds. This prevents unnecessary cache pollution and aligns with the PR intent to restore caching.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}