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🚀 Lazy Barrel Optimization in Rolldown Barrel files, files that re-export from other modules, are common in modern JavaScript projects but a nightmare for your build time. Rolldown now has Lazy Barrel Optimization to fix this. Here's how it works 🧵

You often do not use all functions or components from a library, but they are all exported from a single barrel file. ```js // some-lib/index.js export { a } from './a'; export { b } from './b'; // more exports here [...] // main.js import { a } from 'some-lib'; ```

Real-world impact with Ant Design as example ```js import { Button } from 'antd'; ``` ◆ Without: 2986 modules, ~65ms ◆ With: 250 modules, ~28ms That's 92% fewer modules and 2-4x faster builds.

Rolldown's Lazy Barrel Optimization supports all the patterns you'd expect: ◆ `export * from './components'` ◆ `export { Component } from './Component'` ◆ `export * as ns from './module'` ◆ Mixed exports ◆ Circular references ◆ Self re-exports

Enabling it is simple. Just add this to your Rolldown config: ```js export default { experimental: { lazyBarrel: true, }, }; ``` For Vite 8, you can put it under `build.rolldownOptions`