Inconsistent Dependency Optimization Behavior Between esbuild and rolldown

[sxzz]

Describe the bug

esbuild transforms const and let to var, whereas rolldown does not. This can lead to TDZ errors and incompatibility with vite-plugin-node-polyfills.

// input
const global = globalThis || self;
export { global as default, global };

// esbuild
var global = globalThis || self;
export {
  global as default,
  global
};

// rolldown
//#region index.ts
const global = globalThis || self;

//#endregion
export { global as default, global };

Reproduction

https://bundler.sxzz.dev/#eNpFjEEKwzAMBL8idDZ9gEN/0WMvTiy3ASEVS6EBx3+vCw29zSzLNCwYG66Sab+4fVkw/j3gMnRRMYcH65wYrj+4PVeD4wAjLtNdaH9pdWjnLRlkKmljD+fUp9EjjF436j3gPNJVmbO+BfsHu98vNw==

Steps to reproduce

Try esbuild and rolldown on the reproduction

System Info

N/A

Used Package Manager

pnpm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs and the Rolldown-related guide.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[sapphi-red]

That code doesn't look correct.

import __global_polyfill from './rolldown.js' // this is a importing the current module itself
globalThis.global = __global_polyfill

const global = globalThis || self;

export { global as default, global }

Would you make a reproduction that uses vite-plugin-node-polyfills?

[sxzz]

Reproduction: https://stackblitz.com/edit/vitejs-vite-fysj3txe. Please download it and run it locally rather than directly in StackBlitz.

The code is indeed incorrect, but there is also a compatibility issue.

[sapphi-red]

While I think vite-plugin-node-polyfills would need to fix this on their side as well (since output.topLevelVar can be disabled by users), I decided to enable output.topLevelVar by default as I didn't find any downsides to do so (#380).