biome

What this skill does

# Biome - Fast All-in-One Toolchain

## Overview

Biome is a fast, all-in-one toolchain for web projects written in Rust. It replaces both ESLint and Prettier with a single tool that's 100x faster and provides zero-config defaults.

**Key Features**:
- Single tool for linting and formatting
- 100x faster than ESLint
- Zero configuration by default
- Built-in import sorting
- TypeScript-first design
- Partial Prettier compatibility
- Native monorepo support
- VS Code integration

**Installation**:
```bash
npm install --save-dev @biomejs/biome
```

## Quick Start

### 1. Initialize Biome

```bash
# Create biome.json configuration
npx @biomejs/biome init

# Check your project
npx @biomejs/biome check .

# Fix issues automatically
npx @biomejs/biome check --write .

# Format only
npx @biomejs/biome format --write .

# Lint only
npx @biomejs/biome lint .
```

### 2. Package.json Scripts

```json
{
  "scripts": {
    "check": "biome check .",
    "check:write": "biome check --write .",
    "format": "biome format --write .",
    "lint": "biome lint .",
    "lint:fix": "biome lint --write ."
  }
}
```

### 3. Basic Configuration

```json
{
  "$schema": "https://biomejs.dev/schemas/1.9.4/schema.json",
  "vcs": {
    "enabled": true,
    "clientKind": "git",
    "useIgnoreFile": true
  },
  "files": {
    "ignoreUnknown": false,
    "ignore": ["node_modules", "dist", "build", ".next"]
  },
  "formatter": {
    "enabled": true,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineWidth": 100
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true
    }
  },
  "javascript": {
    "formatter": {
      "quoteStyle": "single",
      "semicolons": "asNeeded",
      "trailingCommas": "all"
    }
  }
}
```

## Core Commands

### Check Command (Recommended)

The `check` command runs both linting and formatting:

```bash
# Check all files
biome check .

# Fix issues automatically
biome check --write .

# Unsafe fixes (may change behavior)
biome check --write --unsafe .

# Apply suggested fixes
biome check --write --unsafe --apply-suggested

# Check specific files
biome check src/**/*.ts

# CI mode (exit with error on issues)
biome ci .
```

### Format Command

Format code without linting:

```bash
# Format all files
biome format --write .

# Check formatting without changing files
biome format .

# Format specific files
biome format --write src/**/*.{ts,tsx,js,jsx}

# Format stdin
echo "const x={a:1}" | biome format --stdin-file-path=file.js
```

### Lint Command

Lint code without formatting:

```bash
# Lint all files
biome lint .

# Fix linting issues
biome lint --write .

# Show rule names
biome lint --verbose .

# Apply unsafe fixes
biome lint --write --unsafe .
```

## Configuration Deep Dive

### Formatter Configuration

```json
{
  "formatter": {
    "enabled": true,
    "formatWithErrors": false,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineEnding": "lf",
    "lineWidth": 80,
    "attributePosition": "auto"
  },
  "javascript": {
    "formatter": {
      "quoteStyle": "single",
      "jsxQuoteStyle": "double",
      "quoteProperties": "asNeeded",
      "trailingCommas": "all",
      "semicolons": "asNeeded",
      "arrowParentheses": "always",
      "bracketSpacing": true,
      "bracketSameLine": false
    }
  },
  "json": {
    "formatter": {
      "trailingCommas": "none"
    }
  }
}
```

### Linter Configuration

```json
{
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "a11y": {
        "recommended": true,
        "noAutofocus": "error",
        "useKeyWithClickEvents": "warn"
      },
      "complexity": {
        "recommended": true,
        "noForEach": "off",
        "useLiteralKeys": "error"
      },
      "correctness": {
        "recommended": true,
        "noUnusedVariables": "error",
        "useExhaustiveDependencies": "warn"
      },
      "performance": {
        "recommended": true,
        "noAccumulatingSpread": "warn"
      },
      "security": {
        "recommended": true,
        "noDangerouslySetInnerHtml": "error"
      },
      "style": {
        "recommended": true,
        "noNonNullAssertion": "warn",
        "useConst": "error",
        "useTemplate": "warn"
      },
      "suspicious": {
        "recommended": true,
        "noExplicitAny": "warn",
        "noArrayIndexKey": "error"
      }
    }
  }
}
```

### File Ignore Patterns

```json
{
  "files": {
    "ignore": [
      "node_modules",
      "dist",
      "build",
      ".next",
      "coverage",
      "*.min.js",
      "public/assets/**"
    ],
    "ignoreUnknown": false,
    "include": ["src/**/*.ts", "src/**/*.tsx"]
  }
}
```

### Override Configuration for Specific Files

```json
{
  "overrides": [
    {
      "include": ["**/*.test.ts", "**/*.spec.ts"],
      "linter": {
        "rules": {
          "suspicious": {
            "noExplicitAny": "off"
          }
        }
      }
    },
    {
      "include": ["scripts/**/*.js"],
      "formatter": {
        "lineWidth": 120
      }
    }
  ]
}
```

## VS Code Integration

### 1. Install Biome Extension

```bash
# Install from VS Code marketplace
code --install-extension biomejs.biome
```

### 2. VS Code Settings (`.vscode/settings.json`)

```json
{
  "[javascript]": {
    "editor.defaultFormatter": "biomejs.biome",
    "editor.formatOnSave": true,
    "editor.codeActionsOnSave": {
      "quickfix.biome": "explicit",
      "source.organizeImports.biome": "explicit"
    }
  },
  "[typescript]": {
    "editor.defaultFormatter": "biomejs.biome",
    "editor.formatOnSave": true,
    "editor.codeActionsOnSave": {
      "quickfix.biome": "explicit",
      "source.organizeImports.biome": "explicit"
    }
  },
  "[typescriptreact]": {
    "editor.defaultFormatter": "biomejs.biome",
    "editor.formatOnSave": true
  },
  "[json]": {
    "editor.defaultFormatter": "biomejs.biome",
    "editor.formatOnSave": true
  },
  "biome.lspBin": "./node_modules/@biomejs/biome/bin/biome"
}
```

### 3. Workspace Settings

```json
{
  "editor.formatOnSave": true,
  "editor.formatOnPaste": true,
  "editor.defaultFormatter": "biomejs.biome",
  "biome.rename": true,
  "files.autoSave": "onFocusChange"
}
```

## Migration from ESLint and Prettier

### 1. Remove Old Tools

```bash
# Remove ESLint and Prettier
npm uninstall eslint prettier eslint-config-prettier \
  eslint-plugin-react eslint-plugin-import \
  @typescript-eslint/parser @typescript-eslint/eslint-plugin

# Remove configuration files
rm .eslintrc.js .eslintrc.json .prettierrc .prettierignore
```

### 2. Migrate Configuration

Use Biome's migration tool:

```bash
# Migrate from Prettier config
biome migrate prettier --write

# Migrate from ESLint config
biome migrate eslint --write
```

### 3. Manual Migration

**Prettier → Biome Formatter**:

```json
// .prettierrc (old)
{
  "semi": false,
  "singleQuote": true,
  "trailingComma": "all",
  "printWidth": 100
}

// biome.json (new)
{
  "formatter": {
    "lineWidth": 100
  },
  "javascript": {
    "formatter": {
      "semicolons": "asNeeded",
      "quoteStyle": "single",
      "trailingCommas": "all"
    }
  }
}
```

**ESLint → Biome Linter**:

```json
// .eslintrc.json (old)
{
  "rules": {
    "no-unused-vars": "error",
    "prefer-const": "warn"
  }
}

// biome.json (new)
{
  "linter": {
    "rules": {
      "correctness": {
        "noUnusedVariables": "error"
      },
      "style": {
        "useConst": "warn"
      }
    }
  }
}
```

### 4. Update Scripts

```json
{
  "scripts": {
    "lint": "biome lint .",
    "lint:fix": "biome lint --write .",
    "format": "biome format --write .",
    "check": "biome check --write ."
  }
}
```

## Git Hooks Integration

### Using Husky + lint-staged

```bash
# Install dependencies
npm install --save-dev husky lint-staged
npx husky init
```

**`.husky/pre-commit`**:
```bash
#!/usr/bin/env sh
. "$(dirname -- "$0")/_/husky.sh"

npx lint-staged
```

**`package.json`**:
```json
{
  "lint-staged": {
    "*.{js,t