Use nollup in development mode

[jthegedus]

Is your feature request related to a problem? Please describe.
The DX of Sapper is great except the speed changes are reflected in browsers in development mode.

Describe the solution you'd like
nollup was suggested in prior conversations as a solution to this problem in development mode without requiring a significant rewrite of the build process of Sapper.

Describe alternatives you've considered
Alternate tools like Snowpack and subsequently Vite have shown that speed of the development-mode builds can be improved significantly. These were discussed in #1204

How important is this feature to you?
DX speed is very important, to the point I am considering rolling Routify or Snowpack with my own SSR instead of Sapper.

Additional context
Prior discussion of Snowpack and Vite

[antony]

Here's where I'm at so far: https://github.com/antony/sapper/tree/feature/alternative-bundlers

You can pass --nollup to the CLI in order to use nollup for dev builds. I've refactored a lot of the way that bundlers are determined and instantiated.

I've realised that nollup doesn't have an API that appears to be compatible with how rollup works, so I've not made it much further, but if somebody who knows about this stuff wants to help, I'd be grateful!

I also know nearly nothing about how typescript works so I came a bit unstuck adding a Bundler type. I've just bunged it into a file called bundlers.ts but I'm assuming that this is wrong, so if somebody has a better idea, please say. Additionally I don't know how to get rid of the duplication of that type in the runtime code.

[rixo]

Unfortunately, Nollup is hard to integrate into Sapper because they both want to be the server / dev server... This will require a quite fat integration layer.

@antony BTW I'm very curious about how you intended to integrate Sapper & Snowpack?

Also, there is currently a bug in Nollup that prevents it to work with Sapper's config. I'm going to work on getting it fixed. (We've recently fixed sourcemaps & HMR CSS injection for Svelte components, yay \o/)

I managed to make it work by heavily hacking both Sapper and Nollup. Speed seems OK. I get ~500ms (client) rebuild time / HMR update on the default starter template. What's great is that I still get about the same time after copying routes/blog/ five times in the sources. So it seems that we can get constant rebuild time independent of the size of the project which, I think, is what we're all after.

Is there someone interested in producing a dummy large Sapper app example we can use to stress test the solutions we come up with?

I'm trying to clean what I have and push a demo soon.

[rixo]

I've pushed my patched everywhere version to the nollup branch of sapper-template-hot: https://github.com/rixo/sapper-template-hot/tree/nollup

It proves that it's possible.

I would love a more meaningful demo app that would allow to better appreciate how it performs.

[rob-balfre]

@rixo I tried adding in a large project of mine to your demo but no luck - just got this error after updating.

GET http://localhost:3002/client/client_wryrwa.[hash].js net::ERR_ABORTED 404 (Not Found)

Maybe I missed something? I can't share the repo unfortunately as its work related.

[benmccann]

You could try adding it to the sample apps if you want a more substantial app:

• https://github.com/sveltejs/realworld
• https://github.com/sveltejs/hn.svelte.dev

They're not huge apps, but it'd be a good start

[rixo]

@rob-balfre I failed to mention: Nollup is spinning its own web server. I have setup it (and hardwired for now) to proxy to localhost:3000, which is expected to be your Sapper server. This means for HMR support (and your bundle files to be available), you need to hit Nollup's server from your browser, at http://localhost:3333 (port also hardcoded in the demo). I think this is your issue.

@benmccann Yup, good idea, I will start with that, thanks :)

[rob-balfre]

@rixo thanks, a few of the page work now but most just error with Uncaught (in promise) TypeError: modules[number] is not a function

[rixo]

@rob-balfre Thanks for trying and the feedback. I'm battling with precisely the same thing in one of my apps, it helps to know I'm not an isolated esoteric case.

I've started to circle in on the cause. Nollup seems to have difficulties with some dynamic imports. We're pushing it to the max here, we're discovering all the bugs >_>

Edit To be completely fair, it seems that the bug has been introduced by my salvage patch of the previous bug. Discussion is ongoing on this one, so I have good hopes that the author of Nollup will be able to offer a more ecological fix.

[rixo]

@rob-balfre I've pushed a possible fix for your error on my nollup#sapper branch.

If you want to retry, just update with:

yarn add -D rixo/nollup#sapper

[rob-balfre]

@rixo tried, but no change I'm afraid.

GET http://localhost:3333/client/client.[hash].js net::ERR_ABORTED 404 (Not Found)