How to use rollup with SvelteKit?

[cayolblake]

Hello all,

Is it possible to use rollup with Sveltekit to generate a bundled and stripped down build? Any tutorial there on doing so?

[eltigerchino]

Doesn't Vite already do this?

[ZetiMente]

pnpm run build

[cayolblake]

@s3812497 no it doesn't. You need uglify or terser through rollup to get this done. Which is what I am trying to do with no luck!

[eltigerchino]

It seems that Vite uses rollup to bundle its dependencies. I'm not sure if this is what you're looking for though.

https://vitejs.dev/guide/why.html#why-not-bundle-with-esbuild

vitejs/vite#7622 (reply in thread)

[david-plugge]

Vite uses rollup and does exactly what you want on npm run build. Have a look at the generated js files inside .svelte-kit/output/client/_app/immutable after executing that command.
If you want to bundle the whole app into a single file have a look at this comment

[cayolblake]

@s3812497 @david-plugge

Vite's rollup does not include treeshaking, or the usage of terser/uglify which removes any JavaScript code that is not used, sometimes called dead code.

In terser for example, compress: {defaults: false, dead_code: true, unused: true} which ends up removing both unused and dead code, in addition to https://rollupjs.org/guide/en/#tree-shaking

Which I am stumbling upon how to do exactly in the newly messed up Vite setup which doesn't allow for an external rollup.conf.js where it was easy to do. 🤦🏼‍♂️

[eltigerchino]

Is it possible to pass on your rollup config options to vite?
https://vitejs.dev/config/build-options.html#build-rollupoptions

It also seems that there's some vite compatibility with rollup plugins
https://vitejs.dev/guide/api-plugin.html#rollup-plugin-compatibility

Could this rollup-terser plugin be used? (I've got no experience with rollup or terser)
https://www.npmjs.com/package/rollup-plugin-terser

[ZetiMente]

Rich Harris is literally the author of Rollup. You think he would sit by and let Sveltekit not have tree shaking ?

You can even use terse if you want but it's not even the best option.