Babel doesn't transform/transpile template code

[Nerixyz]

Version

6.0.0-beta.10

Reproduction link

https://github.com/Nerixyz/vue-rollup-babel-issue

Steps to reproduce

Use @rolup/plugin-babel and @babel/preset-env. Create a component where the template contains code that's not yet supported by a browser (thus needed to be transformed). Write similar unsupported code in a JavaScript file.

What is expected?

Both unsupported versions should be transformed to work in the targeted browser.

What is actually happening?

Only code in the JavaScript file will get transformed, not the template code.

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I've seen a similar issue where the solution was to specify the extensions for the plugin, which I did, however the issue persists. I'd guess I've missed to specify some flag.