Rust Tooling

Comprehensive guide to Rust linting, formatting, type checking, and coverage.

Type Checking: cargo check

Rust's compiler IS the type checker. Fast check without building:

# Check without building
cargo check

# Check all targets (including tests, examples)
cargo check --all-targets

# Check with all features
cargo check --all-features

Linting: Clippy

Installation

Comes with rustup:

rustup component add clippy

Configuration

# Cargo.toml
[lints.clippy]
pedantic = "warn"
nursery = "warn"

# Specific overrides
missing_errors_doc = "allow"
missing_panics_doc = "allow"
module_name_repetitions = "allow"

Or in code:

// lib.rs or main.rs
#![warn(clippy::pedantic)]
#![allow(clippy::module_name_repetitions)]

Commands

# Check
cargo clippy

# Check all targets
cargo clippy --all-targets --all-features

# Fix (where possible)
cargo clippy --fix

# Treat warnings as errors (CI)
cargo clippy -- -D warnings

Lint Categories

Category	Flag	Description
Default	(none)	Common issues
Pedantic	clippy::pedantic	Stricter, opinionated
Nursery	clippy::nursery	Experimental lints
Restriction	clippy::restriction	Very strict

Formatting: rustfmt

Installation

rustup component add rustfmt

Configuration

# rustfmt.toml
edition = "2021"
max_width = 100
tab_spaces = 4
use_small_heuristics = "Default"
imports_granularity = "Module"
group_imports = "StdExternalCrate"
reorder_imports = true

Commands

# Format all
cargo fmt

# Check without modifying (CI)
cargo fmt -- --check

# Format specific file
rustfmt src/lib.rs

Test Coverage: tarpaulin

Installation

cargo install cargo-tarpaulin

Commands

# Generate HTML report
cargo tarpaulin --out Html

# Generate XML for CI
cargo tarpaulin --out Xml

Alternative: llvm-cov

cargo install cargo-llvm-cov
cargo llvm-cov --html

Project Validation

Run all checks:

# Format check + Lint + Tests
cargo fmt -- --check && cargo clippy -- -D warnings && cargo test

# With all features
cargo fmt -- --check && \
cargo clippy --all-targets --all-features -- -D warnings && \
cargo test --all-features

Recommended Cargo.toml Lints

[lints.rust]
unsafe_code = "forbid"

[lints.clippy]
pedantic = "warn"
nursery = "warn"
missing_errors_doc = "allow"
missing_panics_doc = "allow"

CI Configuration

# .github/workflows/ci.yml
name: CI

on: [push, pull_request]

env:
  CARGO_TERM_COLOR: always

jobs:
  check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - uses: dtolnay/rust-toolchain@stable
        with:
          components: rustfmt, clippy

      - uses: Swatinem/rust-cache@v2

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

      - name: Clippy
        run: cargo clippy --all-targets --all-features -- -D warnings

      - name: Test
        run: cargo test --all-features

      - name: Doc
        run: cargo doc --no-deps

With Coverage

      - name: Install tarpaulin
        run: cargo install cargo-tarpaulin

      - name: Coverage
        run: cargo tarpaulin --out Xml

      - uses: codecov/codecov-action@v4

Pre-commit Hook

#!/bin/sh
# .git/hooks/pre-commit
cargo fmt -- --check || exit 1
cargo clippy -- -D warnings || exit 1
cargo test || exit 1

Quick Reference

Operation	Command
Type check	cargo check
Lint check	cargo clippy
Lint fix	cargo clippy --fix
Format check	cargo fmt -- --check
Format fix	cargo fmt
Test	cargo test
Coverage	cargo tarpaulin --out Html
All checks	cargo fmt -- --check && cargo clippy -- -D warnings && cargo test
All fixes	cargo fmt && cargo clippy --fix --allow-dirty

Documentation

# Build docs
cargo doc

# Build and open
cargo doc --open

# Include private items
cargo doc --document-private-items