Make Babel an optional peer dependency

[LoganDark]

When combined with preactjs/prefresh#614, Babel is no longer in the dependency tree.

[rschristian]

Not sure that I love the idea of doing this outside a major, the majority of Vite users will likely experience a (minor) breakage with this as package managers will remove their required Babel deps.

There's a very WIP branch for a new major, I'm thinking it's better to roll this into that.

[LoganDark]

package managers will remove their required Babel deps

Huh? Peer deps aren't automatically uninstalled by package managers...

[rschristian]

Huh? Peer deps aren't automatically uninstalled by package managers...

If you go from dep -> optional peerDep, the pm can remove it, yes. It isn't guaranteed they'll keep around optional peer deps.

I would need to check latest versions as I don't know current behavior off the top of my head, but I know NPM used to consistently do that for sure.

[LoganDark]

Do we know if the majority of Vite users are still depending on Babel? Vite moved away from Babel with 8, didn't it?

[rschristian]

Vite 8 just came out, there's always a long tail of users on older versions (and we support back to Vite 2). Only 18% of Vite users can actually forgo Babel.

Useful tool for comparing usage across major/minor versions

[LoganDark]

Thank you, that's helpful context.

Are you talking about #174? I can retarget that branch if you'd prefer?