bundle-barrel-imports

---

name: bundle-barrel-imports description: Import directly from source files instead of barrel files. Apply when using libraries like lucide-react, @mui/material, or @radix-ui/react-* to reduce bundle size and improve dev boot time.

Avoid Barrel File Imports

Import directly from source files instead of barrel files to avoid loading thousands of unused modules. Barrel files are entry points that re-export multiple modules (e.g., index.js that does export * from './module').

Popular icon and component libraries can have up to 10,000 re-exports in their entry file. For many React packages, it takes 200-800ms just to import them, affecting both development speed and production cold starts.

Why tree-shaking doesn't help: When a library is marked as external (not bundled), the bundler can't optimize it. If you bundle it to enable tree-shaking, builds become substantially slower analyzing the entire module graph.

Incorrect (imports entire library):

Copyimport { Check, X, Menu } from 'lucide-react'
// Loads 1,583 modules, takes ~2.8s extra in dev
// Runtime cost: 200-800ms on every cold start

import { Button, TextField } from '@mui/material'
// Loads 2,225 modules, takes ~4.2s extra in dev

Correct (imports only what you need):

Copyimport Check from 'lucide-react/dist/esm/icons/check'
import X from 'lucide-react/dist/esm/icons/x'
import Menu from 'lucide-react/dist/esm/icons/menu'
// Loads only 3 modules (~2KB vs ~1MB)

import Button from '@mui/material/Button'
import TextField from '@mui/material/TextField'
// Loads only what you use

Alternative (Next.js 13.5+):

Copy// next.config.js - use optimizePackageImports
module.exports = {
  experimental: {
    optimizePackageImports: ['lucide-react', '@mui/material']
  }
}

// Then you can keep the ergonomic barrel imports:
import { Check, X, Menu } from 'lucide-react'
// Automatically transformed to direct imports at build time

Direct imports provide 15-70% faster dev boot, 28% faster builds, 40% faster cold starts, and significantly faster HMR.

Libraries commonly affected: lucide-react, @mui/material, @mui/icons-material, @tabler/icons-react, react-icons, @headlessui/react, @radix-ui/react-*, lodash, ramda, date-fns, rxjs, react-use.

Reference: How we optimized package imports in Next.js