@rollup/plugin-babel: Babel 8 compatibility?

[tagliala]

Hello,

Babel 8 has just been released. I've seen an attempt to upgrade to 8.0 last year, in #1889, which has been closed as "abandoned".

Does this mean that there will not be a @rollup/plugin-babel supporting Babel 8?

• Rollup Plugin Name: @rollup/plugin-babel
• Rollup Plugin Version: 7.1.0

Feature Use Case

Use with Babel 8 and meet peer dependencies constraints without warnings

├─┬ @rollup/plugin-babel 7.1.0
│ └── ✕ unmet peer @babel/core@^7.0.0: found 8.0.0

Feature Proposal

Official Babel 8 compatibility

[sueun-dev]

Can't speak to the maintainers' plans, but functionally 7.1.0 already works with Babel 8. I ran a rollup build with @rollup/plugin-babel@7.1.0 + @babel/core@8.0.0 + @babel/preset-env@8.0.0 and it transpiled fine: arrow funcs, optional chaining, and private fields all downleveled using Babel 8's helpers. The plugin just calls @babel/core's transform API, which still behaves the same.

So the unmet-peer is only the declared range (@babel/core: ^7.0.0), not a real break. Heads up that preset-env 8.0.0 adds a second offender (its transitive @babel/preset-modules peer also excludes core 8, and preset-env 8.0.2 fixes that). To silence both at once in pnpm:

"pnpm": { "peerDependencyRules": { "allowedVersions": { "@babel/core": "8" } } }

(verified: zero peer warnings, deps resolve). On npm, --legacy-peer-deps.

You can use it today. Whether 7.x gets an official peer bump is the maintainers' call (the earlier #1889 was abandoned).

[vanbukin]

@shellscape any plans?

[itsjamie]

I opened a PR here: #2021

I've done a pass of a few things related to https://github.com/video-dev/hls.js, I'm hoping to bring down the bundle size and it looks like upgrading to Babel 8 and pushing forward the terser version will net a ~3KB saving after Brotli compression on JSDelivr which will net back ~19TB of bandwidth over the year. The CDN is nice enough to give free bandwidth so I figured I can help them out 🙂