rugged-gemini: Skill for Claude Code

Rust Idioms and Patterns

Rust type system + ownership model = primary correctness tools. Lean into compiler — strongest ally. Idiomatic, safe, expressive.

Scope: Rust coding idioms. Layout: @.gemini/skills/project-structure-rust/SKILL.md. Test naming: GEMINI.md § Testing Strategy. Logging: @.gemini/skills/logging-and-observability-principles/SKILL.md.

Ownership and Borrowing

1. Prefer borrowing (&T, &mut T) over cloning. Never .clone() to silence borrow checker without // CLONE: comment. Use Cow<'_, T> when may/may not need ownership. Prefer &str over String, &[T] over Vec<T> in params.

2. Minimize owned data in structs. References + lifetimes for short-lived. Owned types when struct outlives inputs.

3. Avoid unnecessary Arc<Mutex<T>>: channels for one-directional, RwLock for read-heavy, Arc<T> (no lock) for immutable-after-init.

Error Handling

1. ? for propagation — never unwrap() in production. Acceptable only in tests, infallible ops with // SAFETY: comment, CLI main() with expect("reason").

2. Error crates by context: library = thiserror (typed enums), application = anyhow (ergonomic chaining). Never mix: libs must not depend on anyhow.

3. Error type design:

// ✅ Typed, matchable
#[derive(Debug, thiserror::Error)]
pub enum PathfinderError {
    #[error("file not found: {path}")]
    FileNotFound { path: PathBuf },
    #[error("AST parse failed: {0}")]
    ParseError(String),
    #[error(transparent)]
    Io(#[from] std::io::Error),
}

// ❌ Stringly-typed, unmatchable
fn do_thing() -> Result<(), String> { ... }

// ✅ Force callers to handle
#[must_use]
pub fn create_task(req: CreateTaskRequest) -> Result<Task, TaskError> { ... }

Async and Concurrency

1. tokio runtime. #[tokio::main]/#[tokio::test]. tokio::spawn over std::thread::spawn. tokio::select! for racing futures.

2. Cancellation safety: prefer tokio::sync::mpsc over broadcast. Document cancellation on async fns holding resources across .await. Use CancellationToken for shutdown.