---

name: rust-code-quality description: Apply rustfmt and clippy linting standards for consistent, safe Rust code. Use before commits and in CI pipelines.

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.