|
| 1 | +--- |
| 2 | +description: 'Rust programming language coding conventions and best practices' |
| 3 | +applyTo: '**/*.rs' |
| 4 | +--- |
| 5 | + |
| 6 | +# Rust Coding Conventions and Best Practices |
| 7 | + |
| 8 | +Follow idiomatic Rust practices and community standards when writing Rust code. |
| 9 | + |
| 10 | +These instructions are based on [The Rust Book](https://doc.rust-lang.org/book/), [Rust API Guidelines](https://rust-lang.github.io/api-guidelines/), [RFC 430 naming conventions](https://github.com/rust-lang/rfcs/blob/master/text/0430-finalizing-naming-conventions.md), and the broader Rust community at [users.rust-lang.org](https://users.rust-lang.org). |
| 11 | + |
| 12 | +## General Instructions |
| 13 | + |
| 14 | +- Always prioritize readability, safety, and maintainability. |
| 15 | +- Use strong typing and leverage Rust's ownership system for memory safety. |
| 16 | +- Break down complex functions into smaller, more manageable functions. |
| 17 | +- For algorithm-related code, include explanations of the approach used. |
| 18 | +- Write code with good maintainability practices, including comments on why certain design decisions were made. |
| 19 | +- Handle errors gracefully using `Result<T, E>` and provide meaningful error messages. |
| 20 | +- For external dependencies, mention their usage and purpose in documentation. |
| 21 | +- Use consistent naming conventions following [RFC 430](https://github.com/rust-lang/rfcs/blob/master/text/0430-finalizing-naming-conventions.md). |
| 22 | +- Write idiomatic, safe, and efficient Rust code that follows the borrow checker's rules. |
| 23 | +- Ensure code compiles without warnings. |
| 24 | + |
| 25 | +## Patterns to Follow |
| 26 | + |
| 27 | +- Use modules (`mod`) and public interfaces (`pub`) to encapsulate logic. |
| 28 | +- Handle errors properly using `?`, `match`, or `if let`. |
| 29 | +- Use `serde` for serialization and `thiserror` or `anyhow` for custom errors. |
| 30 | +- Implement traits to abstract services or external dependencies. |
| 31 | +- Structure async code using `async/await` and `tokio` or `async-std`. |
| 32 | +- Prefer enums over flags and states for type safety. |
| 33 | +- Use builders for complex object creation. |
| 34 | +- Split binary and library code (`main.rs` vs `lib.rs`) for testability and reuse. |
| 35 | +- Use `rayon` for data parallelism and CPU-bound tasks. |
| 36 | +- Use iterators instead of index-based loops as they're often faster and safer. |
| 37 | +- Use `&str` instead of `String` for function parameters when you don't need ownership. |
| 38 | +- Prefer borrowing and zero-copy operations to avoid unnecessary allocations. |
| 39 | + |
| 40 | +### Ownership, Borrowing, and Lifetimes |
| 41 | + |
| 42 | +- Prefer borrowing (`&T`) over cloning unless ownership transfer is necessary. |
| 43 | +- Use `&mut T` when you need to modify borrowed data. |
| 44 | +- Explicitly annotate lifetimes when the compiler cannot infer them. |
| 45 | +- Use `Rc<T>` for single-threaded reference counting and `Arc<T>` for thread-safe reference counting. |
| 46 | +- Use `RefCell<T>` for interior mutability in single-threaded contexts and `Mutex<T>` or `RwLock<T>` for multi-threaded contexts. |
| 47 | + |
| 48 | +## Patterns to Avoid |
| 49 | + |
| 50 | +- Don't use `unwrap()` or `expect()` unless absolutely necessary—prefer proper error handling. |
| 51 | +- Avoid panics in library code—return `Result` instead. |
| 52 | +- Don't rely on global mutable state—use dependency injection or thread-safe containers. |
| 53 | +- Avoid deeply nested logic—refactor with functions or combinators. |
| 54 | +- Don't ignore warnings—treat them as errors during CI. |
| 55 | +- Avoid `unsafe` unless required and fully documented. |
| 56 | +- Don't overuse `clone()`, use borrowing instead of cloning unless ownership transfer is needed. |
| 57 | +- Avoid premature `collect()`, keep iterators lazy until you actually need the collection. |
| 58 | +- Avoid unnecessary allocations—prefer borrowing and zero-copy operations. |
| 59 | + |
| 60 | +## Code Style and Formatting |
| 61 | + |
| 62 | +- Follow the Rust Style Guide and use `rustfmt` for automatic formatting. |
| 63 | +- Keep lines under 100 characters when possible. |
| 64 | +- Place function and struct documentation immediately before the item using `///`. |
| 65 | +- Use `cargo clippy` to catch common mistakes and enforce best practices. |
| 66 | + |
| 67 | +## Error Handling |
| 68 | + |
| 69 | +- Use `Result<T, E>` for recoverable errors and `panic!` only for unrecoverable errors. |
| 70 | +- Prefer `?` operator over `unwrap()` or `expect()` for error propagation. |
| 71 | +- Create custom error types using `thiserror` or implement `std::error::Error`. |
| 72 | +- Use `Option<T>` for values that may or may not exist. |
| 73 | +- Provide meaningful error messages and context. |
| 74 | +- Error types should be meaningful and well-behaved (implement standard traits). |
| 75 | +- Validate function arguments and return appropriate errors for invalid input. |
| 76 | + |
| 77 | +## API Design Guidelines |
| 78 | + |
| 79 | +### Common Traits Implementation |
| 80 | +Eagerly implement common traits where appropriate: |
| 81 | +- `Copy`, `Clone`, `Eq`, `PartialEq`, `Ord`, `PartialOrd`, `Hash`, `Debug`, `Display`, `Default` |
| 82 | +- Use standard conversion traits: `From`, `AsRef`, `AsMut` |
| 83 | +- Collections should implement `FromIterator` and `Extend` |
| 84 | +- Note: `Send` and `Sync` are auto-implemented by the compiler when safe; avoid manual implementation unless using `unsafe` code |
| 85 | + |
| 86 | +### Type Safety and Predictability |
| 87 | +- Use newtypes to provide static distinctions |
| 88 | +- Arguments should convey meaning through types; prefer specific types over generic `bool` parameters |
| 89 | +- Use `Option<T>` appropriately for truly optional values |
| 90 | +- Functions with a clear receiver should be methods |
| 91 | +- Only smart pointers should implement `Deref` and `DerefMut` |
| 92 | + |
| 93 | +### Future Proofing |
| 94 | +- Use sealed traits to protect against downstream implementations |
| 95 | +- Structs should have private fields |
| 96 | +- Functions should validate their arguments |
| 97 | +- All public types must implement `Debug` |
| 98 | + |
| 99 | +## Testing and Documentation |
| 100 | + |
| 101 | +- Write comprehensive unit tests using `#[cfg(test)]` modules and `#[test]` annotations. |
| 102 | +- Use test modules alongside the code they test (`mod tests { ... }`). |
| 103 | +- Write integration tests in `tests/` directory with descriptive filenames. |
| 104 | +- Write clear and concise comments for each function, struct, enum, and complex logic. |
| 105 | +- Ensure functions have descriptive names and include comprehensive documentation. |
| 106 | +- Document all public APIs with rustdoc (`///` comments) following the [API Guidelines](https://rust-lang.github.io/api-guidelines/). |
| 107 | +- Use `#[doc(hidden)]` to hide implementation details from public documentation. |
| 108 | +- Document error conditions, panic scenarios, and safety considerations. |
| 109 | +- Examples should use `?` operator, not `unwrap()` or deprecated `try!` macro. |
| 110 | + |
| 111 | +## Project Organization |
| 112 | + |
| 113 | +- Use semantic versioning in `Cargo.toml`. |
| 114 | +- Include comprehensive metadata: `description`, `license`, `repository`, `keywords`, `categories`. |
| 115 | +- Use feature flags for optional functionality. |
| 116 | +- Organize code into modules using `mod.rs` or named files. |
| 117 | +- Keep `main.rs` or `lib.rs` minimal - move logic to modules. |
| 118 | + |
| 119 | +## Quality Checklist |
| 120 | + |
| 121 | +Before publishing or reviewing Rust code, ensure: |
| 122 | + |
| 123 | +### Core Requirements |
| 124 | +- [ ] **Naming**: Follows RFC 430 naming conventions |
| 125 | +- [ ] **Traits**: Implements `Debug`, `Clone`, `PartialEq` where appropriate |
| 126 | +- [ ] **Error Handling**: Uses `Result<T, E>` and provides meaningful error types |
| 127 | +- [ ] **Documentation**: All public items have rustdoc comments with examples |
| 128 | +- [ ] **Testing**: Comprehensive test coverage including edge cases |
| 129 | + |
| 130 | +### Safety and Quality |
| 131 | +- [ ] **Safety**: No unnecessary `unsafe` code, proper error handling |
| 132 | +- [ ] **Performance**: Efficient use of iterators, minimal allocations |
| 133 | +- [ ] **API Design**: Functions are predictable, flexible, and type-safe |
| 134 | +- [ ] **Future Proofing**: Private fields in structs, sealed traits where appropriate |
| 135 | +- [ ] **Tooling**: Code passes `cargo fmt`, `cargo clippy`, and `cargo test` |
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