What is the reasoning behind using Rollup for ESM builds, why even bundle?

[johot]

Thank you for an awesome project!

I tried it yesterday and it just works for the most part! I am testing different way of outputting an internal React component library. So far I have been using just tsc for this but needed support for babel plugins etc. I started by exploring just running Babel 7 via the CLI myself (and tsc for type declarations) and this worked out great but now ofc I have a lot of scripts and build tools to keep track of.

I then found tsdx and really like the zero config approach. The only thing that I am a bit puzzled about is why tsdx wants to bundle my library, ie output a single index.es.js file rather than multiple files?

For something like a TypeScript -> ESM Modules with ES5/ES6 syntax build do I really gain anything from bundling the files if my consuming app will do it anyways using Webpack? What is the reason to use Rollup at all inside tsdx rather than just doing a Babel + Tsc emitDeclarationOnly)? I am trying to understand if I am missing something :)

Thank you once again and keep up the great work!