Code Linting Guide

A comprehensive guide to code linting across different programming languages

What is Linting?

Linting is the process of running a program that analyzes code for potential errors, bugs, stylistic errors, and suspicious constructs. It helps maintain code quality, consistency, and prevents potential runtime issues.

Code Quality Static Analysis Best Practices

ESLint

Installation

npm install eslint --save-dev
npx eslint --init

Configuration (.eslintrc.json)

{
  "env": {
    "browser": true,
    "es2021": true
  },
  "extends": "eslint:recommended",
  "rules": {
    "indent": ["error", 2],
    "quotes": ["warn", "single"]
  }
}

Pylint

Installation

pip install pylint
pylint --generate-rcfile > .pylintrc

Configuration (.pylintrc)

[MESSAGES CONTROL]
disable=C0111,C0103

[FORMAT]
max-line-length=100
indent-string='    '

Common Linting Issues

Error: Undefined Variable

// ❌ Bad
console.log(undefinedVar);

// ✅ Good
const definedVar = 'Hello';
console.log(definedVar);

Warning: Unused Variable

// ⚠️ Warning
function calculate(a, b) {
    const unused = 'test';
    return a + b;
}

// ✅ Good
function calculate(a, b) {
    return a + b;
}

Pre-commit Hooks

Using Husky (JavaScript)

npm install husky --save-dev
npx husky install
npx husky add .husky/pre-commit "npm run lint"