rust-best-practices

Prefer borrowing with &T unless you need an owned copy, such as for caching, Arc/Rc pointers, or APIs requiring ownership. Avoid cloning large structures like Vec or HashMap, and use &str over String and &[T] over Vec<T> in function parameters.

Use thiserror for library code where callers need precise, typed errors with #[from] conversions. Reserve anyhow for binaries where ergonomic error propagation matters more than exact error types, since anyhow erases error context callers might need.

Run cargo clippy --all-targets --all-features --locked -- -D warnings to check libraries, tests, benches, and examples with warnings treated as errors. Optionally add -W clippy::pedantic or -W clippy::nursery for stricter checks.

Use type state when you need compile-time state safety, such as preventing a client from sending messages before connecting. Avoid it for trivial states, when runtime flexibility is required, or when it leads to overly complex generic signatures.

Most slowness comes from building without the --release flag, so always benchmark release builds. Use cargo flamegraph to visualize CPU time per function and cargo clippy -- -D clippy::perf for performance lint hints before optimizing.

Avoid snapshots for simple primitives, small structs, critical-path logic, and flaky or randomly generated output unless redacted. Snapshot testing works best for generated code, serialized complex data, rendered HTML, and CLI output.