Fix disappearing polyfills when conflicting versions of preset are used

[ertrzyiks]

Q	A
Fixed Issues?	Fixes #12545
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link	No
Any Dependency Changes?	No
License	MIT

If the preset-env is applied twice and

• one version includes the extension change from Add js extension to preset-env generated polyfill imports #10862
• the other version does not include the change

The core-js polyfills are removed from the bundle.

Example of breaking configuration can be found in the demo project:
https://github.com/ertrzyiks/babel-loader-lost-polyfills-demo

The demo project uses preset-env and preset-react-app. The minimal configuration causing polyfills to disappear is the following:

presets: [
  [
    // => Found "@babel/preset-env@7.12.11"
    require('@babel/preset-env').default,
    { corejs: 3, useBuiltIns: 'entry' }
  ],
  [
    //=> Found "babel-preset-react-app#@babel/preset-env@7.12.1"
    require('babel-preset-react-app/node_modules/@babel/preset-env').default, 
    { corejs: 3, useBuiltIns: 'entry' }
  ],
]

Updated snapshots

The two updated snapshots are for cases when the input importing specific files like

import 'core-js/modules/es.symbol';
import 'core-js/modules/es.object.from-entries';
import 'core-js/modules/esnext.string.replace-all';

so judging by the purpose of the original PR introducing the extensions won't be problematic: the original imports are kept untouched. No autogenerated code without .js extension though.

[babel-bot]

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[JLHwung]

Can you add test cases when input file contains core-js imports ending with .js?

[ertrzyiks]

Makes sense 👍 is this single scenario enough or you had more cases in mind?
28f6547

[nicolo-ribaudo]

It's possible that this will also be fixed by #12583

[nicolo-ribaudo]

@ertrzyiks #12583 doesn't fix this bug, but since we are replacing our polyfills injection logic I have copied this PR to babel/babel-polyfills#56 (also, I figured out how to properly add a test).

Thanks for the help anyway, and I set you as the author of the commits in the other repo!

[ertrzyiks]

@nicolo-ribaudo makes sense, thanks for letting me know and all the help with my very first PR. It was unexpectedly easy to work with such complex codebase. We can close this PR, right?

[nicolo-ribaudo]

I don't know if #12583 will be merged before the next release, so I think it's better to keep this open for now.

[nicolo-ribaudo]

The 7.13.0 release that replaces this transform is taking way longer than expected, and this PR is a good fix until 7.13.0.