Unnecessary polyfilling + wrongly renaming imports

[anilanar]

I babelify + auto polyfill node_modules too; because it's usually unclear what ES version+browser libraries target nowadays. After switching to babel-polyfills (corejs3), one curious case failed.

For esm5/esm2015 builds of rxjs@6.6.3; in node_modules/rxjs/_esm5/index.js:

• babel-polyfills adds import _Observable from "core-js-pure/features/observable/index.js"; at the top of the file.
• then replaces some (or all) occurences of the term Observable with _Observable.
• rxjs has a re-export export { Observable } from './internal/Observable';. babel-polyfills replaces that with export { _Observable as Observable } from './internal/Observable';
• bundler rightfully complains that there's no _Observable in ./internal/Observable.

I see two problems here:

1. Why polyfill Observable in this case? Observable is imported (or re-exported) from somewhere, it's not the global Observable.
2. Even if it polyfills, why break the imports?

[anilanar]

It's actually the proposals flag that causes the issue (because Observable is a proposal), which is broken for @babel/plugin-transform-runtime too.

[nicolo-ribaudo]

Thanks for the bug report! It turns out this is not only for proposals, but it was a generic bug with export ... from.

[nicolo-ribaudo]

This will be fixed when babel/babel#12395 is released. In the meaintinme, you can exclude that file by adding ignore: ["node_modules/rxjs/_esm5/index.js"] to your Babel config.

PS. Thanks for reporting these bugs!

[nicolo-ribaudo]

Fixed in @babel/types@7.12.10