Publish as ESM

[dynst]

This would solve...

undici/package.json

Lines 62 to 63 in 74d505f

	"main": "index.js",
	"types": "index.d.ts",

Bundlers are much better at tree-shaking ESM than they are at CJS.

The implementation should look like...

undici/package.json

Line 65 in 74d505f

"build:node": "esbuild index-fetch.js --bundle --platform=node --outfile=undici-fetch.js --define:esbuildDetection=1 --keep-names && node scripts/strip-comments.js",

Build with a transpiler like tsdown instead of esbuild.

I have also considered...

Additional context

https://antfu.me/posts/move-on-to-esm-only
https://joyeecheung.github.io/blog/2024/03/18/require-esm-in-node-js/

Node.js v18 support was already dropped last year, so there's no compatibility benefit in (dual-)publishing CommonJS code at this point. #3880

[metcoder95]

I get the idea of ESM better for tree shaking, but overall, are you facing any problem with the current setup or are you having big bundle sizes in the current setup?
and why we should move to tsdown instead of esbuild, what's the reason to do so?