Support for Rspack

[justin808]

See #225.

Let's see if we can get a PR showing https://www.rspack.dev/guide/start/introduction works.

[tomdracz]

TLDR; if there's interest, let's try to get some initial proof of concept of this and then figure out best way of handling integration.

FWIW I would love to see a proof of concept, but reviewing the docs of rspack, I feel there are fair few things that make it not quite out of the box experience.

Different plugins, packages (something that we rely on - webpack manifest plugin is not compatible for example and needs rspack equivalent) make the migration harder and supporting both more burdensome. We've been getting some Webpack-specific support queries lately and having another setup variation will make it harder to respond to those IMO.

I'd personally rather see a separate package that builts on top of/can be replacement to Shakapacker JS one, than bloating up the current one. After all, JS package is kinda optional, as long there's a manifest, the Ruby part can hook into it.

Long term, maybe there's a world where there's a "base" Shakapacker JS package with webpacker/rspack/whatever adapter?

[jeffbax]

Just leaving a note to say that we'd definitely have interest in a path toward migrating to rspack -- our webpack builds are extremely non-performant at this point on our host Heroku, frequently running into memory build issues that we do our best to work around by building in another environment where we can (though you can't for things like preview apps).

Especially if it is built to be largely compatible.