Cannot set core-js version for helper-only transformation in `@babel/tranform-runtime`

Feature Request

Is your feature request related to a problem? Please describe.

Basically we are trying to resolve this issue in @vue/babel-preset-app:

https://github.com/babel/babel/issues/6628 How can we write ES20xx and ship the smallest amount of code (for a given target environment)?

To be more specific, this item:

• babel helpers: reference the same helpers instead of recreating per file (either via /packages/babel-plugin-transform-runtime@7.0#options

• To achieve that we need to combine @babel/preset-env with @babel/transform-runtime, and the latter one is only used to do helper transformation.
• The default runtime has a blocking issue though, see https://github.com/babel/babel/issues/7597
• So to circumvent it we have to use @babel/runtime-corejs2. I know it’s not the best solution but it’s an acceptable compromise/tradeoff in practice.
• Before beta.56 we were able to disable polyfills option while still referring the helper functions to @babel/runtime-corejs2.
• But after this commit, polyfills option is removed because it is now the default behavior.
• An unintended consequence is that we can no longer point helpers to any other runtime package without introducing core-js polyfills along with it.

Describe the solution you’d like

Bring back the polyfills option, allowing the user to opt-out it while still being able to specify a core-js version for helpers.

Describe alternatives you’ve considered N/A

Teachability, Documentation, Adoption, Migration Strategy N/A

[nicolo-ribaudo]

As a workaround, you can use https://github.com/tleunen/babel-plugin-module-resolver to alias @babel/runtime -> @babel/runtime-corejs2

[nicolo-ribaudo]

I’m closing this issue, since it’s possible to transpile @babel/runtime with @babel/preset-env to add polyfills.