differential bundling

[Rich-Harris]

this is a great idea, let's steal it

https://twitter.com/benjamn/status/1003735863921082370

[maxmilton]

That sounds amazing! Would probably be fun implementing in https://github.com/sveltejs/sapper-template eventually too.

[Rich-Harris]

This is implemented in 0.18.7. Currently it only works for Rollup apps — here's a template: https://github.com/sveltejs/sapper-template-rollup/tree/babel (it might make sense for that to be the master branch, haven't decided).

Documentation to come (https://github.com/sveltejs/sapper.svelte.technology/issues/30) but it's pretty simple — vary the client build config based on process.env.SAPPER_LEGACY_BUILD and use the --legacy flag, and Sapper takes it from there. It will use the modern build for apps that support async functions, and the legacy build for everything else.

[Conduitry]

Might it even make sense to have the webpack and rollup templates in the same repo on different branches? I'm assuming there are quite a few files that are identical among all versions (webpack/rollup and regular/legacy). We could master be just purely the app and assets and a readme, and put all the actual build stuff in different branches on top of that. Then we just tell people to npx degit sveltejs/sapper-template#rollup-legacy or whatever.

[Rich-Harris]

Probably, yeah... in fact you can even have webpack and rollup in the same project, and do sapper build --bundler webpack or sapper build --bundler rollup if you're the kind of person who struggles with commitment. Though separate branches in the same repo is probably the right approach

[arxpoetica]

Said this in the forum:

FWIW, I find it confusing to tag --legacy on a build -- makes it seem like it's only doing something old