Clippy Advanced

---
created: 2025-12-16
modified: 2026-05-09
reviewed: 2025-12-16
name: clippy-advanced
description: "Advanced Clippy configuration for Rust — custom rules, pedantic/nursery lints, clippy.toml, IDE and CI integration. Use when configuring or enforcing lint standards."
user-invocable: false
allowed-tools: Bash, Read, Grep, Glob
---

# clippy-advanced - Advanced Clippy Configuration

Advanced Clippy configuration for comprehensive Rust linting, including custom rules, lint categories, disallowed methods, and IDE integration.

## When to Use This Skill

| Use this skill when... | Use another tool instead when... |
|------------------------|----------------------------------|
| Configuring Clippy lint rules | Formatting code (use rustfmt) |
| Setting up CI linting for Rust | Building/compiling (use cargo build) |
| Customizing clippy.toml | Running tests (use cargo test) |
| Enforcing code standards | Managing dependencies (use cargo add) |

## Installation

```bash
# Clippy is included with rustup
rustup component add clippy

# Verify installation
cargo clippy --version

# Update clippy with rust toolchain
rustup update
```

## Basic Usage

```bash
# Run clippy on current project
cargo clippy

# Run on all targets (lib, bins, tests, examples, benches)
cargo clippy --all-targets

# Run with all features enabled
cargo clippy --all-features

# Run on workspace
cargo clippy --workspace --all-targets --all-features

# Show detailed lint explanations
cargo clippy -- -W clippy::all -A clippy::pedantic

# Treat warnings as errors
cargo clippy -- -D warnings
```

## Lint Categories

| Category | Purpose | Default |
|----------|---------|---------|
| `clippy::correctness` | Likely bugs | Deny |
| `clippy::complexity` | Overly complex code | Warn |
| `clippy::perf` | Performance issues | Warn |
| `clippy::style` | Code style | Warn |
| `clippy::suspicious` | Code that looks wrong | Warn |
| `clippy::pedantic` | Opinionated style | Off |
| `clippy::restriction` | Opt-in constraints | Off |
| `clippy::nursery` | Experimental | Off |
| `clippy::cargo` | Cargo.toml issues | Off |

### Recommended Cargo.toml Configuration

```toml
[workspace.lints.clippy]
# Deny correctness issues (likely bugs)
correctness = "deny"
complexity = "warn"
perf = "warn"
style = "warn"
suspicious = "warn"

# Enable pedantic but allow some noisy lints
pedantic = "warn"
must_use_candidate = "allow"
missing_errors_doc = "allow"

# Enable some restriction lints selectively
clone_on_ref_ptr = "warn"
dbg_macro = "warn"
print_stdout = "warn"
todo = "warn"
unimplemented = "warn"
unwrap_used = "warn"

# Enable nursery lints (experimental)
use_self = "warn"
```

## clippy.toml Essential Settings

Create `clippy.toml` in project root for thresholds and disallowed items:

```toml
cognitive-complexity-threshold = 15
too-many-lines-threshold = 100
too-many-arguments-threshold = 5

disallowed-methods = [
  { path = "std::env::var", reason = "Use std::env::var_os for better Unicode handling" },
  { path = "std::process::exit", reason = "Use Result propagation instead" },
]

disallowed-names = ["foo", "bar", "baz"]
```

## Lint Suppression

```rust
// Function-level
#[allow(clippy::too_many_arguments)]
fn complex_function(a: i32, b: i32, c: i32, d: i32, e: i32, f: i32) {}

// Module-level (src/lib.rs)
#![warn(clippy::all)]
#![warn(clippy::pedantic)]
#![deny(clippy::unwrap_used)]
#![allow(clippy::module_name_repetitions)]

// Inline
#[allow(clippy::cast_possible_truncation)]
let x = value as u8;
```

## Agentic Optimizations

| Context | Command |
|---------|---------|
| CI strict | `cargo clippy --workspace --all-targets -- -D warnings` |
| JSON output | `cargo clippy --message-format=json` |
| Compact errors | `cargo clippy --message-format=short` |
| Quick check | `cargo clippy --message-format=short -- -D warnings` |
| Pedantic check | `cargo clippy -- -W clippy::pedantic -D clippy::correctness` |

## Quick Reference

### Command-Line Flags

| Flag | Description |
|------|-------------|
| `--all-targets` | Check lib, bins, tests, examples, benches |
| `--all-features` | Enable all features |
| `--workspace` | Check entire workspace |
| `--message-format=json` | JSON output for tooling |
| `--message-format=short` | Compact error format |
| `-- -D warnings` | Treat warnings as errors |
| `-- -W clippy::pedantic` | Enable pedantic lints |
| `-- -A clippy::lint_name` | Allow specific lint |

### Lint Levels

| Level | Attribute | Effect |
|-------|-----------|--------|
| Allow | `#[allow(...)]` | Suppress lint |
| Warn | `#[warn(...)]` | Show warning |
| Deny | `#[deny(...)]` | Compile error |

## References

- [Clippy documentation](https://doc.rust-lang.org/clippy/)
- [Lint list](https://rust-lang.github.io/rust-clippy/master/)
- [Configuration options](https://doc.rust-lang.org/clippy/configuration.html)
- [rust-analyzer integration](https://rust-analyzer.github.io/manual.html)

For detailed configuration examples, CI integration, IDE setup, and best practices, see [REFERENCE.md](REFERENCE.md).