Conventions & Style Guide

Q: Edition 2024 required?

When edition = "2024" in workspace Cargo.toml; match manifest, not blog posts.

Q: Import order?

rustfmt handles groups; rust-analyzer organize imports on save optional.

Team-wide Rust idioms reduce review friction: rustfmt formatting, clippy policy, naming, module layout, and error handling split.

Recipe

cargo fmt --all
cargo clippy --all-targets --all-features -- -D warnings

# rustfmt.toml (repo root)
edition = "2024"
max_width = 100

When to reach for this:

Writing or reviewing any PR
Onboarding new hires
Updating CI lint policy

Working Example

Naming

// modules and files: snake_case
mod billing_tax;
 
// types: PascalCase
struct LineItem;
 
// functions: snake_case
fn calculate_tax() {}
 
// constants: SCREAMING_SNAKE_CASE
const MAX_RETRIES: u32 = 3;

Errors

// crates/domain - library
#[derive(thiserror::Error, Debug)]
pub enum DomainError { /* ... */ }
 
// crates/api - binary
fn main() -> anyhow::Result<()> { Ok(()) }

Module layout

src/
  lib.rs or main.rs
  routes/        # HTTP only in api crate
  error.rs
  state.rs

Deep Dive

Clippy Policy

Level	Rule
Deny	`unwrap_used` in production `src/` (allow in tests)
Deny	`pedantic` subset team selects
Allow	Documented with `#[allow(clippy::...)]` + reason

Commit Messages

feat(api): add readiness probe [API-55]
fix(domain): reject zero-quantity line [BILL-12]

Imperative subject, ticket ID, body explains why.

API Documentation

Public items need /// with example compiling in rustdoc:

/// Adds two quantities.
///
/// # Example
/// ```
/// assert_eq!(add(1, 2), 3);
/// ```
pub fn add(a: u32, b: u32) -> u32 { a + b }

Gotchas

Formatting debates in PR - wasted time. Fix: rustfmt auto in CI.
allow clippy globally - hides real issues. Fix: line-level allows with comment.
unwrap in lib - panics surprise callers. Fix: Result or expect with invariant comment in tests only.
Inconsistent error types per module - fragmentation. Fix: one enum per crate.
Missing pub(crate) - over-exposed API. Fix: minimal visibility.

Alternatives

Alternative	Use When	Don't Use When
Stricter pedantic	Safety-critical	Early startup velocity
Custom rustfmt width	Long generics	Unless team agrees

FAQs

Edition 2024 required?

When edition = "2024" in workspace Cargo.toml; match manifest, not blog posts.

Import order?

rustfmt handles groups; rust-analyzer organize imports on save optional.

Stack versions: This page was written for Rust 1.97.0 (edition 2024), Tokio 1.x, Axum 0.8, serde 1.0, sqlx 0.8, clap 4, and Polars 0.46+.

Working Example

// modules and files: snake_case
mod billing_tax;
 
// types: PascalCase
struct LineItem;
 
// functions: snake_case
fn calculate_tax() {}
 
// constants: SCREAMING_SNAKE_CASE
const MAX_RETRIES: u32 = 3;

// crates/domain - library
#[derive(thiserror::Error, Debug)]
pub enum DomainError { /* ... */ }
 
// crates/api - binary
fn main() -> anyhow::Result<()> { Ok(()) }

src/
  lib.rs or main.rs
  routes/        # HTTP only in api crate
  error.rs
  state.rs

Deep Dive

Level	Rule
Deny	`unwrap_used` in production `src/` (allow in tests)
Deny	`pedantic` subset team selects
Allow	Documented with `#[allow(clippy::...)]` + reason

feat(api): add readiness probe [API-55]
fix(domain): reject zero-quantity line [BILL-12]

Imperative subject, ticket ID, body explains why.

Public items need /// with example compiling in rustdoc:

/// Adds two quantities.
///
/// # Example
/// ```
/// assert_eq!(add(1, 2), 3);
/// ```
pub fn add(a: u32, b: u32) -> u32 { a + b }

Gotchas

Formatting debates in PR - wasted time. Fix: rustfmt auto in CI.

allow clippy globally - hides real issues. Fix: line-level allows with comment.

unwrap in lib - panics surprise callers. Fix: Result or expect with invariant comment in tests only.

Inconsistent error types per module - fragmentation. Fix: one enum per crate.

Missing pub(crate) - over-exposed API. Fix: minimal visibility.

Alternative

Use When

Don't Use When

Stricter pedantic

Safety-critical

Early startup velocity

Custom rustfmt width

Long generics

Unless team agrees

Conventions & Style Guide

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Conventions & Style Guide