Jon Chery
4e433158cd
---ci--- project: atelier phase: 3 milestone: v0.4 status: complete phase_role: execution phase_tag: v0.3.3 requirements: covered: [ATELIER-102, ATELIER-103, ATELIER-104, ATELIER-105] partial: [] ---/ci---
86 lines
3.4 KiB
Markdown
86 lines
3.4 KiB
Markdown
# Rust — Language Application
|
|
|
|
> How Atelier's domain principles apply in Rust specifically. Derives from `domains/` docs.
|
|
|
|
## Derived Docs
|
|
|
|
- [rs-ownership.md](rs-ownership.md) — Send/Sync, lifetimes, borrowing, ownership transfer.
|
|
- [rs-tooling.md](rs-tooling.md) — cargo, clippy, fmt, edition discipline.
|
|
- [rs-async.md](rs-async.md) — tokio, async traits, cancellation, pin.
|
|
- [rs-testing.md](rs-testing.md) — #[test], proptest, property testing, mock discipline.
|
|
|
|
## Type System (C1 Correctness, Data P7 Type Fidelity)
|
|
|
|
- **Newtypes for domain concepts:** `struct UserId(String);` — zero-cost, type-safe.
|
|
- **`enum` for finite domains:** `enum Status { Pending, Paid, Shipped }` — exhaustive.
|
|
- **No `unsafe` without justification and review:** `unsafe` opts out of the compiler's guarantees.
|
|
|
|
```rust
|
|
struct UserId(String);
|
|
struct OrderId(String);
|
|
// Cannot pass OrderId where UserId is expected
|
|
fn get_user(id: UserId) -> Result<User, Error> { ... }
|
|
```
|
|
|
|
## Error Handling (Errors P1 Errors are Data)
|
|
|
|
- **`Result<T, E>` for fallible operations:** errors are values, not exceptions.
|
|
- **`thiserror` for error enums, `anyhow` for applications:**
|
|
```rust
|
|
#[derive(thiserror::Error)]
|
|
enum AppError {
|
|
#[error("not found: {0}")]
|
|
NotFound(String),
|
|
#[error("validation: {0}")]
|
|
Validation(String),
|
|
#[error(transparent)]
|
|
Io(#[from] std::io::Error),
|
|
}
|
|
```
|
|
- **`?` for propagation, not `unwrap()`:** `unwrap()` panics in production.
|
|
- **No `panic::catch_unwind` for control flow:** panics are for bugs, not errors.
|
|
|
|
## Concurrency (Concurrency — Rust's ownership model)
|
|
|
|
- **`Send` and `Sync` traits enforced by the compiler:** data races are compile errors.
|
|
- **`Arc<T>` for shared, `Mutex<T>`/`RwLock<T>` for mutation:** the lock is explicit.
|
|
- **`tokio` for async:** `async fn`, `.await`. Bounded channels (`tokio::sync::mpsc::channel(N)`).
|
|
- **`Drop` for cleanup:** no leaked resources (no `defer` needed; RAII).
|
|
|
|
```rust
|
|
async fn fetch_with_timeout(url: &str) -> Result<Response, Error> {
|
|
tokio::time::timeout(Duration::from_secs(5), fetch(url)).await??;
|
|
}
|
|
```
|
|
|
|
## Immutability (Concurrency P1 Immutability by Default)
|
|
|
|
- **Variables are immutable by default:** `let x = 5;` not `let mut x = 5;`.
|
|
- **`&T` (shared ref) over `&mut T` (exclusive ref):** the compiler enforces aliasing rules.
|
|
- **Interior mutability (`Cell`/`RefCell`) only when needed:** not as a default.
|
|
|
|
## Nullability (C1)
|
|
|
|
- **`Option<T>`, not nullable pointers:** `Some(x)` / `None`. The compiler enforces handling.
|
|
- **No `null`:** Rust has no null. `Option::None` is the explicit absence.
|
|
- **`?` on `Option` for propagation:** `fn get_name(user: User) -> Option<String> { user.profile?.name }`.
|
|
|
|
## Testing (Testing)
|
|
|
|
- **`#[test]` + `#[cfg(test)] mod tests`:** tests co-located.
|
|
- **`proptest` or `quickcheck` for property-based tests:** edge case coverage (P9).
|
|
- **`tokio::test` for async tests.**
|
|
- **No `SystemTime::now()` in tests:** inject an `Instant` or a mock clock.
|
|
|
|
## Observability (Observability P1)
|
|
|
|
- **`tracing` crate:** structured logs + spans + traces. Not `println!`.
|
|
- **`tracing::instrument` on functions:** automatic span context.
|
|
- **`tracing-subscriber` with JSON format:** structured output for production.
|
|
|
|
## Tooling (DevOps P2)
|
|
|
|
- **`cargo clippy`:** lint. `cargo clippy -- -D warnings` in CI.
|
|
- **`cargo fmt`:** format.
|
|
- **`cargo test`:** tests. `cargo test --release` for perf-sensitive.
|
|
- **Committed `Cargo.lock`:** reproducible builds (even for libraries, for CI). |