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Lint

A versatile linting tool with multiple interfaces: CLI, MCP (Model Context Protocol), and library.

Features

  • CLI Interface: Run linting from the command line
  • MCP Server: Expose linting capabilities via MCP protocol
  • Library API: Use linting functionality in your Rust projects

Installation

cargo install --path .

Usage

CLI

Lint files or directories:

# Lint current directory
lint lint .

# `check` is an alias for `lint`
lint check .

# Lint specific files
lint lint src/main.rs src/lib.rs

# Use glob patterns
lint lint "src/**/*.rs"

# Specify output format (text, json, markdown, github, sarif, junit, concise, gitlab)
lint lint . --output json

# --output-format is an alias for --output
lint lint . --output-format markdown

# Set maximum line length
lint lint . --max-line-length 120

# Enable specific rules
lint lint . -r line-length -r trailing-whitespace

# Use a configuration file
lint lint . --config .lint.json

# Config is auto-discovered: place .lint.json in your project root
# and run lint without --config

# .gitignore patterns are automatically respected when walking directories

# Auto-fix fixable issues
lint lint . --fix

# Preview fixes without writing changes
lint lint . --diff

# Apply fixes but don't report remaining violations
lint lint . --fix-only

# Auto-add suppression comments to all violations
lint lint . --add-noqa

# Ignore all suppression comments (useful for auditing)
lint lint . --ignore-suppressions

# Ignore all ignore patterns (lint everything including node_modules)
lint lint . --no-ignore

# Watch for changes and re-lint
lint lint . --watch

# Use cache to skip unchanged files
lint lint . --cache

# Use a custom cache file location
lint lint . --cache --cache-location /tmp/lint_cache.json

# Use content-based caching (more accurate, slower)
lint lint . --cache --cache-strategy content

# Only show errors (suppress warnings and infos)
lint lint . --quiet

# Fail if more than 10 warnings
lint lint . --max-warnings 10

# Disable colored output
lint lint . --color never

# Add a rule to the default set
lint lint . --select no-todo

# Remove a rule from the default set
lint lint . --ignore line-length

# Enable the final-newline rule
lint lint . --select final-newline

# Enable the no-mixed-line-endings rule
lint lint . --select no-mixed-line-endings

# Enable all built-in rules
lint lint . --select-all

# Enable all rules in a category
lint lint . --select style
lint lint . --select security
lint lint . --select correctness,style

# Ignore all rules in a category
lint lint . --ignore security
lint lint . --ignore style

# Only lint files that have uncommitted changes (fast pre-commit hook)
lint lint . --changed

# Only lint staged files
lint lint . --staged

# Load a plugin rule pack
lint lint . --plugin security

# Load multiple plugins
lint lint . --plugin security --plugin javascript

# Don't respect .gitignore (lint generated files too)
lint lint . --no-gitignore

# Force exclude ignored files even when explicitly passed
lint lint . --force-exclude

# Disable source context in output
lint lint . --no-show-source

# List files that would be linted (without linting)
lint lint . --print-files

# Write JSON results to a file
lint lint . --output json --output-file results.json

# Generate SARIF output for GitHub Advanced Security
lint lint . --output sarif --output-file results.sarif.json

# Generate JUnit XML for CI integration
lint lint . --output junit --output-file results.junit.xml

# Generate GitLab Code Quality report
lint lint . --output gitlab --output-file gl-code-quality-report.json

# Concise one-line-per-violation output
lint lint . --output concise

# Show progress bar while linting (useful for large repos)
lint lint . --progress

# Show violations without failing the build
lint lint . --exit-zero

# Show effective configuration after merging all sources
lint lint . --show-settings

# Enable specific rules
lint lint . --select no-tabs --select no-consecutive-empty-lines

# Show per-rule violation statistics
lint lint . --statistics

# Exclude specific paths or patterns
lint lint . --exclude vendor --exclude "*.min.js"

# Don't fail when a glob pattern doesn't match any files
lint lint "nonexistent/**/*.rs" --no-error-on-unmatched-pattern

# Treat warnings as errors (exit 1 on any warning)
lint lint . --deny-warnings

# Exit non-zero even if all violations were fixed
lint lint . --fix --exit-non-zero-on-fix

# Lint code from stdin (useful for editor integrations)
echo 'let x = 5;   ' | lint lint --stdin --stdin-filename test.rs

# Validate configuration file (catches unknown rules, plugins, etc.)
lint lint . --validate-config

# Set maximum allowed nesting depth (default: 4)
lint lint . --max-nesting-depth 3

# Set maximum function length in lines (default: 50)
lint lint . --max-function-lines 30

# Detect out-of-order imports (supports Rust, JS/TS, Python, C/C++, Go)
lint lint . --rules sort-imports

# List available rules
lint list-rules

# Explain what a specific rule does
lint explain line-length

# Show version
lint version

# Generate a default configuration file
lint init

Exit codes: 0 if no issues found, 1 if any errors detected or if warnings exceed --max-warnings.

Config Extends

Share a base configuration across projects:

{
  "extends": ".lint.base.json",
  "max_line_length": 120,
  "rule_set": {
    "enabled_rules": ["line-length", "trailing-whitespace", "no-todo"]
  }
}

Values in the local config override the base. Collections like ignore_patterns, per_file_ignores, and severity_overrides are merged.

Per-Directory Configuration

Place a .lint.toml or .lint.json in any subdirectory to override settings for files in that tree:

# src/.lint.toml — stricter rules for source code
max_line_length = 80
enabled_rules = ["line-length", "trailing-whitespace", "no-todo", "no-tabs"]
# tests/.lint.toml — relaxed rules for tests
max_line_length = 120
ignore_patterns = ["test_data"]

Per-directory configs are merged with the base config. Supported overrides: max_line_length, enabled_rules, plugins, ignore_patterns, per_file_ignores, severity_overrides.

Unused Suppression Detection

Enable the unused-suppression rule to detect suppression comments that don't actually suppress any violations (useful for cleanup after refactoring):

lint lint . --rules line-length,trailing-whitespace,unused-suppression

This reports warnings like:

Unused suppression comment: `lint: ignore=line-length`

MCP Server

Run the MCP server:

cargo run --bin lint-mcp -- --host 127.0.0.1 --port 8080

The server exposes the following tools:

  • lint_files: Lint specified files and return issues
  • list_rules: List all available linting rules

LSP Server

Run the Language Server Protocol (LSP) server for real-time diagnostics in editors:

cargo run --bin lint-lsp -- --stdio

Or install and use with your editor:

cargo install --path .
# Then configure your editor to run `lint-lsp --stdio`

Supported LSP methods:

  • initialize / initialized
  • textDocument/didOpen — lint opened files and publish diagnostics
  • textDocument/didChange — re-lint on change and publish diagnostics
  • textDocument/didClose — clear diagnostics
  • shutdown / exit

Pre-commit Hook

Use lint with pre-commit:

repos:
  - repo: https://github.com/yingkitw/lint
    rev: v0.1.3
    hooks:
      - id: lint

To lint only changed files (faster for large repos):

repos:
  - repo: https://github.com/yingkitw/lint
    rev: v0.1.3
    hooks:
      - id: lint
        args: ['--changed']

To lint only staged files:

repos:
  - repo: https://github.com/yingkitw/lint
    rev: v0.1.3
    hooks:
      - id: lint
        args: ['--staged']

Library

Use as a library in your Rust project:

use lint::{ConfigBuilder, OutputFormat};

fn main() -> anyhow::Result<()> {
    let config = ConfigBuilder::new()
        .paths(vec!["src".into()])
        .max_line_length(Some(100))
        .enabled_rules(vec![
            "line-length".to_string(),
            "trailing-whitespace".to_string(),
        ])
        .output_format(OutputFormat::Json)
        .build();

    let results = lint::lint_files(&config)?;

    for result in results {
        println!("File: {}", result.file_path.display());
        for message in result.messages {
            println!("  {}: {}", message.severity.as_str(), message.message);
        }
    }

    Ok(())
}

Available Rules

All violations include fix suggestions to help resolve issues. Use --output text to see → help: messages, or --output markdown for **Fix**: blocks.

Universal Rules

  • line-length: Lines exceeding max length → break line, extract variable, or use continuation
  • trailing-whitespace: Trailing spaces/tabs → remove
  • no-todo: TODO/FIXME comments → address or create tracking issue

JavaScript/TypeScript Rules

  • no-console-log: console.log/warn/error → use logger
  • no-var: var usage → use let/const
  • missing-semicolon: Missing semicolons

Python Rules

  • no-print: print() → use logging module
  • python-style: PEP 8 (PascalCase classes, snake_case functions)

Go Rules

  • go-style: Exported functions need documentation

Java Rules

  • java-style: PascalCase classes, no System.out → use SLF4J
  • missing-semicolon: Missing semicolons

Rust Rules

  • no-unwrap: .unwrap() → use ? or match
  • no-expect: .expect() → use ? or match
  • missing-semicolon: Missing semicolons

Ruby Rules

  • no-puts: puts → use Logger
  • ruby-style: CamelCase classes, attr_writer for setters

PHP Rules

  • no-echo: echo → use error_log or return JSON

Swift Rules

  • no-swift-print: print() → use OSLog

Kotlin Rules

  • kotlin-style: PascalCase classes, println → use slf4j

Dart Rules

  • no-dart-print: print() → use debugPrint or logging package

C# Rules

  • no-csharp-console: Console.WriteLine → use ILogger
  • csharp-style: PascalCase classes

Shell Rules

  • shell-echo-quote: Unquoted variables in echo → quote with "$VAR"

SQL Rules

  • sql-no-select-star: SELECT * → list explicit columns

Lua Rules

  • no-lua-print: print() → use logging or remove

Scala Rules

  • no-scala-println: println() → use slf4j

R Rules

  • no-r-print: print() → use message() or cat()

Zig Rules

  • no-zig-debug-print: std.debug.print → remove or use std.log

HTML Rules

  • html-no-inline-style: Inline style= → move to CSS class
  • html-img-alt: img without alt → add alt for accessibility

CSS Rules

  • css-avoid-important: !important → increase selector specificity

Configuration

Create a custom configuration:

let config = ConfigBuilder::new()
    .paths(vec!["src".into(), "tests".into()])
    .ignore_patterns(vec![
        "node_modules".to_string(),
        "target".to_string(),
        ".git".to_string(),
    ])
    .max_line_length(Some(120))
    .enabled_rules(vec![
        "line-length".to_string(),
        "trailing-whitespace".to_string(),
    ])
    .custom_rules(Some("custom_rules.json".into()))
    .output_format(OutputFormat::Text)
    .build();

Custom Rules

Define your own rules in a JSON file:

[
  {
    "name": "no-debugger",
    "pattern": "\\bdebugger\\b",
    "message": "Debugger statement found",
    "severity": "Error",
    "suggestion": "Remove debugger before committing",
    "extensions": ["js", "ts"]
  }
]
  • name: Unique rule identifier
  • pattern: Regular expression to match
  • message: Error/warning message
  • severity: Error, Warning, or Info
  • suggestion: Optional fix hint
  • extensions: Optional list of file extensions to apply the rule to

Suppressing Rules Inline

Suppress a rule on a specific line:

let x = 5; // lint: ignore=line-length

Suppress all rules on a line:

let x = 5; // lint: ignore

Block Suppressions

Disable a rule for a block of code:

// lint: disable=line-length
const LONG_CONFIG: &str = "some very long configuration string that exceeds normal limits";
// lint: enable=line-length

Disable all rules for a block:

// lint: disable
const GENERATED_DATA: &str = "...generated content...";
// lint: enable

File-Level Ignore

Ignore all rules for an entire file (must be on the first line):

// lint: ignore-file
// This file is auto-generated
const DATA: &str = "...";

Ignore a specific rule for the entire file:

// lint: ignore-file=line-length
// Test files often have long lines

Works in any language — the suppression comment is language-agnostic.

Per-File Ignore Patterns

Disable specific rules for files matching a glob pattern via config:

{
  "per_file_ignores": {
    "tests/**/*.rs": ["line-length"],
    "gen/**/*.js": ["line-length", "trailing-whitespace"]
  }
}

Rule Severity Override

Override the default severity of any rule in your config:

{
  "severity_overrides": {
    "line-length": "Error",
    "no-todo": "Warning"
  }
}

Valid severities: Error, Warning, Info.

Supported File Extensions

  • Rust: .rs
  • JavaScript/TypeScript: .js, .ts, .jsx, .tsx
  • Python: .py
  • Java: .java
  • Go: .go
  • C/C++: .c, .cpp, .h, .hpp
  • Ruby: .rb
  • PHP: .php
  • Swift: .swift
  • Kotlin: .kt
  • Dart: .dart
  • C#: .cs
  • Shell: .sh, .bash
  • SQL: .sql
  • Lua: .lua
  • Scala: .scala
  • R: .r
  • Zig: .zig
  • HTML: .html, .htm
  • CSS: .css, .scss, .sass

Output Formats

  • Text: Human-readable output (default)
  • Json: Machine-readable JSON format
  • Markdown: Markdown-formatted output
  • GitHub: GitHub Actions workflow commands (::error file=...::...)

Benchmarking

Run the built-in performance benchmark:

cargo run --example bench

This generates 100 files (500 lines each) and measures linting throughput. The linter processes multiple files in parallel using rayon for better performance on multi-core machines.

Contributing

If you find this project helpful, please consider giving it a star ⭐️

Feedback, issues, and pull requests are welcome! Feel free to open an issue for bug reports, feature requests, or questions.

License

Apache-2.0

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