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tessl/npm-eslint-plugin-unicorn

More than 100 powerful ESLint rules for enforcing code quality, consistency, and modern JavaScript best practices

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Overview
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Files

import-export-rules.mddocs/

Import and Export Rules

Rules governing module imports, exports, and dependency management for better module organization.

Capabilities

Import Style Rules

Rules for consistent import patterns and module loading.

/**
 * Enforces consistent import style patterns
 */
'unicorn/import-style': 'error' | 'warn' | 'off' | [
  'error' | 'warn',
  {
    checkImport?: boolean; // Default: true
    checkDynamicImport?: boolean; // Default: false
    checkExportFrom?: boolean; // Default: false
    checkRequire?: boolean; // Default: false
    extendDefaultStyles?: boolean; // Default: true
    styles?: Record<string, {
      named?: 'camelCase' | 'kebabCase' | 'pascalCase' | false;
      default?: 'camelCase' | 'kebabCase' | 'pascalCase' | false;
      namespace?: 'camelCase' | 'kebabCase' | 'pascalCase' | false;
      unassigned?: boolean;
    }>;
  }
];

/**
 * Prefers node: protocol for Node.js built-in modules
 */
'unicorn/prefer-node-protocol': 'error' | 'warn' | 'off';

/**
 * Requires specific module specifiers for imports
 */
'unicorn/require-module-specifiers': 'error' | 'warn' | 'off' | [
  'error' | 'warn',
  {
    patterns?: Record<string, string>;
  }
];

Usage Examples:

// ❌ Bad - inconsistent import style
import * as fs from 'fs';
import { readFile } from 'fs';

// ✅ Good - consistent import style (prefer named imports)
import { readFile, writeFile } from 'node:fs';

// ❌ Bad - missing node: protocol
import fs from 'fs';
import path from 'path';
import util from 'util';

// ✅ Good - using node: protocol
import fs from 'node:fs';
import path from 'node:path';
import util from 'node:util';

// ❌ Bad - bare module specifier when specific version needed
import lodash from 'lodash';

// ✅ Good - specific module specifier (if configured)
import lodash from 'lodash-es';

Export Pattern Rules

Rules for consistent export patterns and module structure.

/**
 * Prevents anonymous default exports
 */
'unicorn/no-anonymous-default-export': 'error' | 'warn' | 'off';

/**
 * Prefers export-from syntax for re-exports
 */
'unicorn/prefer-export-from': 'error' | 'warn' | 'off' | [
  'error' | 'warn',
  {
    ignoreUsedVariables?: boolean; // Default: false
  }
];

/**
 * Prevents named default imports and exports
 */
'unicorn/no-named-default': 'error' | 'warn' | 'off';

Usage Examples:

// ❌ Bad - anonymous default export
export default function() {
  return 'helper';
}

// ✅ Good - named default export
export default function helper() {
  return 'helper';
}

// ❌ Bad - manual re-export
import { utility } from './utils.js';
export { utility };

// ✅ Good - export-from syntax
export { utility } from './utils.js';

// ❌ Bad - named default import
import { default as React } from 'react';

// ✅ Good - regular default import
import React from 'react';

Module System Rules

Rules for consistent module system usage and patterns.

/**
 * Prefers ES modules over CommonJS
 */
'unicorn/prefer-module': 'error' | 'warn' | 'off' | [
  'error' | 'warn',
  {
    checkDefaultCase?: boolean; // Default: false
  }
];

/**
 * Prefers import.meta properties over alternatives
 */
'unicorn/prefer-import-meta-properties': 'error' | 'warn' | 'off';

Usage Examples:

// ❌ Bad - CommonJS patterns in ES modules
const path = require('path');
module.exports = { helper };

// ✅ Good - ES module patterns
import path from 'node:path';
export { helper };

// ❌ Bad - __dirname in ES modules
const currentDir = __dirname;

// ✅ Good - import.meta.url
const currentDir = new URL('.', import.meta.url).pathname;

// ❌ Bad - __filename alternative
const currentFile = __filename;

// ✅ Good - import.meta.url for filename
const currentFile = new URL(import.meta.url).pathname;

Dynamic Import Rules

Rules for proper dynamic import usage.

/**
 * Import style rules also apply to dynamic imports when configured
 */
'unicorn/import-style': [
  'error',
  {
    checkDynamicImport: true, // Enable dynamic import checking
  }
];

Usage Examples:

// ❌ Bad - inconsistent dynamic import (if configured to prefer named)
const module = await import('lodash');

// ✅ Good - consistent with static import style
const { debounce } = await import('lodash');

// Dynamic imports with proper error handling
try {
  const { processData } = await import('./data-processor.js');
  await processData(input);
} catch (error) {
  console.error('Failed to load data processor:', error);
}

Package.json and Module Configuration

Rules for package.json and module resolution patterns.

/**
 * Requires specific patterns in package.json imports/exports
 * (This would be configured through require-module-specifiers)
 */
'unicorn/require-module-specifiers': [
  'error',
  {
    patterns: {
      'lodash': 'lodash-es', // Prefer ES module version
      'react-dom': 'react-dom/client', // Prefer specific entry point
    }
  }
];

Usage Examples:

// ❌ Bad - using CommonJS version when ES module preferred
import _ from 'lodash';

// ✅ Good - using ES module version
import _ from 'lodash-es';

// ❌ Bad - using legacy entry point
import { render } from 'react-dom';

// ✅ Good - using modern entry point
import { createRoot } from 'react-dom/client';

Conditional Imports and Exports

Rules for handling conditional module loading.

/**
 * Import style rules can be configured for different environments
 */
'unicorn/import-style': [
  'error',
  {
    styles: {
      'node:fs': {
        named: 'camelCase',
        default: false, // Discourage default import
      },
      'react': {
        default: 'pascalCase',
        named: 'camelCase',
      }
    }
  }
];

Usage Examples:

// Environment-specific imports
if (typeof window !== 'undefined') {
  // Browser-specific imports
  const { browserUtil } = await import('./browser-utils.js');
} else {
  // Node.js-specific imports  
  const { readFile } = await import('node:fs/promises');
}

// Conditional exports in package.json would be:
// {
//   "exports": {
//     "node": "./dist/node.js",
//     "default": "./dist/browser.js"
//   }
// }

TypeScript Import Rules

Rules specific to TypeScript import patterns.

/**
 * Import style rules for TypeScript-specific patterns
 */
'unicorn/import-style': [
  'error',
  {
    styles: {
      '@types/*': {
        default: false, // Types should use named imports
        named: 'camelCase',
      }
    }
  }
];

Usage Examples:

// ❌ Bad - default import for types
import Express from '@types/express';

// ✅ Good - named imports for types
import { Request, Response } from '@types/express';

// Type-only imports
import type { User } from './types.js';
import type { ApiResponse } from './api-types.js';

// Mixed imports
import { processUser, type UserConfig } from './user-utils.js';

Configuration Examples

Comprehensive Import/Export Rules

export default [
  {
    plugins: {
      unicorn: eslintPluginUnicorn,
    },
    rules: {
      // Import style consistency
      'unicorn/import-style': [
        'error',
        {
          checkImport: true,
          checkDynamicImport: true,
          styles: {
            'node:fs': { named: 'camelCase', default: false },
            'node:path': { named: 'camelCase', default: false },
            'lodash': { named: 'camelCase', default: false },
            'react': { default: 'pascalCase' },
          }
        }
      ],
      
      // Module system preferences
      'unicorn/prefer-node-protocol': 'error',
      'unicorn/prefer-module': 'error',
      'unicorn/prefer-import-meta-properties': 'error',
      
      // Export patterns
      'unicorn/no-anonymous-default-export': 'error',
      'unicorn/prefer-export-from': 'error',
      'unicorn/no-named-default': 'error',
      
      // Module specifiers
      'unicorn/require-module-specifiers': [
        'error',
        {
          patterns: {
            'lodash': 'lodash-es',
            'react-dom': 'react-dom/client',
          }
        }
      ],
    },
  },
];

Node.js-Specific Configuration

export default [
  {
    plugins: {
      unicorn: eslintPluginUnicorn,
    },
    rules: {
      // Require node: protocol for all built-ins
      'unicorn/prefer-node-protocol': 'error',
      
      // Prefer ES modules
      'unicorn/prefer-module': 'error',
      'unicorn/prefer-import-meta-properties': 'error',
      
      // Node.js import style
      'unicorn/import-style': [
        'error',
        {
          styles: {
            'node:fs': { named: 'camelCase' },
            'node:fs/promises': { named: 'camelCase' },
            'node:path': { named: 'camelCase' },
            'node:url': { named: 'camelCase' },
            'node:util': { named: 'camelCase' },
          }
        }
      ],
    },
  },
];

React Project Configuration

export default [
  {
    plugins: {
      unicorn: eslintPluginUnicorn,
    },
    rules: {
      // React-friendly import styles
      'unicorn/import-style': [
        'error',
        {
          styles: {
            'react': { default: 'pascalCase' },
            'react-dom/client': { named: 'camelCase' },
            '@types/react': { named: 'pascalCase' },
          }
        }
      ],
      
      // Export patterns for components
      'unicorn/no-anonymous-default-export': 'error',
      'unicorn/prefer-export-from': ['error', { ignoreUsedVariables: true }],
      
      // Modern module patterns
      'unicorn/prefer-module': 'error',
      'unicorn/require-module-specifiers': [
        'error',
        {
          patterns: {
            'react-dom': 'react-dom/client'
          }
        }
      ],
    },
  },
];

docs

anti-pattern-prevention-rules.md

array-object-rules.md

code-quality-rules.md

code-style-rules.md

dom-browser-rules.md

import-export-rules.md

index.md

modern-javascript-rules.md

plugin-configuration.md

tile.json