Rust Code Quality

Code Quality

Maintain consistent, safe Rust code with rustfmt and clippy.

Rustfmt Configuration

Create rustfmt.toml in project root:

max_width = 100
edition = "2021"
imports_granularity = "Crate"
group_imports = "StdExternalCrate"
reorder_imports = true

Run before every commit:

cargo fmt
cargo fmt --check  # CI mode (fails if not formatted)

Clippy Configuration

Add to lib.rs or main.rs:

#![warn(clippy::all, clippy::pedantic)]
#![deny(clippy::unwrap_used)]
#![deny(clippy::expect_used)]
#![warn(missing_docs)]

Or in Cargo.toml:

[lints.clippy]
all = "warn"
pedantic = "warn"
unwrap_used = "deny"
expect_used = "deny"

Run clippy:

cargo clippy
cargo clippy -- -D warnings  # CI mode (fails on warnings)

Recommended Clippy Lints

// Deny dangerous patterns
#![deny(clippy::unwrap_used)]        // Use ? or expect with context
#![deny(clippy::expect_used)]        // Use proper error handling
#![deny(clippy::panic)]              // No panics in library code
#![deny(clippy::todo)]               // No TODOs in production

// Warn on style issues
#![warn(clippy::pedantic)]           // Stricter lints
#![warn(clippy::nursery)]            // Experimental lints
#![warn(clippy::cargo)]              // Cargo.toml lints
#![warn(missing_docs)]               // Document public items

CI Integration

GitHub Actions example:

name: Rust CI
on: [push, pull_request]

jobs:
  check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable
        with:
          components: rustfmt, clippy

      - name: Format check
        run: cargo fmt --check

      - name: Clippy
        run: cargo clippy -- -D warnings

      - name: Tests
        run: cargo test

Common Clippy Fixes

// Bad: clippy::unwrap_used
let value = some_option.unwrap();

// Good: Use ? operator
let value = some_option.ok_or(Error::MissingValue)?;

// Bad: clippy::clone_on_ref_ptr
let arc2 = arc1.clone();

// Good: Use Arc::clone for clarity
let arc2 = Arc::clone(&arc1);

// Bad: clippy::redundant_closure
items.iter().map(|x| process(x))

// Good: Pass function directly
items.iter().map(process)

Pre-commit Hook

Create .git/hooks/pre-commit:

#!/bin/sh
cargo fmt --check || exit 1
cargo clippy -- -D warnings || exit 1

Guidelines

• Run cargo fmt before every commit
• Fix all clippy warnings before merging
• Use #[allow(clippy::...)] sparingly with justification
• Enable pedantic lints for library code
• Document all public items

Examples

See hercules-local-algo/src/lib.rs for lint configuration.

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