rust-standards— agent skill

Testing

• Unit tests in #[cfg(test)] modules within each source file
• Integration tests in tests/ directory

Naming

• No get_ prefix: fn name() not fn get_name()
• Iterator convention: iter() / iter_mut() / into_iter()
• Conversion naming: as_ (cheap &), to_ (expensive), into_ (ownership)
• Static var prefix: G_CONFIG for static, no prefix for const

Data Types

• Use newtypes: struct Email(String) for domain semantics
• Prefer slice patterns: if let [first, .., last] = slice
• Pre-allocate: Vec::with_capacity(), String::with_capacity()
• Avoid Vec abuse: use arrays for fixed sizes

Strings

• Prefer &str over String in function parameters
• Use String for ownership: return String when transferring ownership
• Prefer bytes: s.bytes() over s.chars() when ASCII
• Use Cow<str> when you might need to modify borrowed data
• Use format! over string concatenation with +
• Avoid nested iteration: contains() on string is O(n\*m)

Error Handling

• Use ? for all fallible operations
• unwrap() in tests only, never production
• expect() only for provably impossible states; the message must justify why it can't fail e.g. expect("regex is valid: validated at compile time")
• unwrap_or / unwrap_or_else / unwrap_or_default for deliberate fallbacks
• Assertions for invariants: assert! at function entry

Memory

• Meaningful lifetimes: 'src, 'ctx not just 'a
• try_borrow() for RefCell to avoid panic
• Shadowing for transformation: let x = x.parse()?

Concurrency

• Identify lock ordering to prevent deadlocks
• Atomics for primitives, not Mutex for bool/usize
• Choose memory order carefully: Relaxed/Acquire/Release/SeqCst

Async

• Sync for CPU-bound; async is for I/O
• Don't hold locks across await: use scoped guards

Macros

• Avoid unless necessary: prefer functions/generics
• Follow Rust syntax: macro input should look like Rust

Deprecated → Better

• lazy_static! → std::sync::OnceLock (since 1.70)
• once_cell::Lazy → std::sync::LazyLock (since 1.80)
• std::sync::mpsc → crossbeam::channel only if you need multi-consumer or better performance under contention; std::sync::mpsc is fine for most use cases
• failure/error-chain → thiserror/anyhow
• try!() → ? operator (since 2018)

Docs

• All pub methods must have /// doc comments
• All /// doc comments must be extremely concise
• Imperative mood: Returns the length not This function returns the length
• Don't restate the name: fn connect() doesn't need "Connects to the server"
• Document the non-obvious: panics, errors, surprising edge cases; skip obvious params/returns
• No filler: no "This method...", "Note that...", "Please be aware..."
• # Examples only for non-trivial usage; doctests must compile and pass
• Don't write doctests purely for coverage; write them only when the example genuinely aids understanding

Quick Reference

Naming: snake_case (fn/var), CamelCase (type), SCREAMING_CASE (const)
Format: rustfmt (just use it)
Docs: /// for public items, //! for module docs
Lint: #![deny(clippy::all, clippy::pedantic)]

Miscellaneous

• Derive Debug on all public types; derive Clone, PartialEq only when needed
• Use clippy with #![deny(clippy::all, clippy::pedantic)] - fix all warnings
• No unsafe blocks
• Modules: one file per module, mod.rs only for re-exports