fix(v2): Resolve IE11 compatibility issues (Fixes #1784)

[andresmanelli]

Motivation

I need to create a site that is compatible with IE11 and I like the simplicity of this project.

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

I just ran yarn test and had the same result than v2.0.0-alpha.25 (I think because of Windows paths)

This is a screenshot of the website in IE11 (not perfect, but ok)

Related PRs

None

Disclaimer: I am no web developer :) so all reviews are welcome. Thanks!

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[endiliey]

I think it's overkill to polyfill whole corejs.
Why not just polyfill object.assign ?

https://github.com/sindresorhus/object-assign is a good solution.

WDYT ?

[andresmanelli]

I will try that, although I found other issues when only importing that specific method from core-js.

I'll let you know asap

[endiliey]

ie11 polyfill from cra https://github.com/facebook/create-react-app/blob/master/packages/react-app-polyfill/ie11.js

naturally it will be best if we can utilize it like babel preset env browserslist integration because importing "core-js" loads polyfills for every possible ECMAScript feature: what if you know that you only need some of them?

[endiliey]

Currently our babel-preset-env use the default options

docusaurus/packages/docusaurus/src/webpack/utils.ts

Line 91 in d5ca17f

presets: ['@babel/env', '@babel/react'],

Maybe can utilize https://babeljs.io/docs/en/babel-preset-env#usebuiltins 'usage'
so that polyfills will be added automatically when the usage of some feature is unsupported in target environment

[andresmanelli]

I added the useBuiltIns option, but I'm not able no build locally any more due to #1782 I think (maybe netlify/docusaurus-2/deploy-preview has the same issue?)

[endiliey]

the error is not related to #1782

maybe usebuiltins option doesnt work.

[andresmanelli]

I can confirm the addition of the useBuiltIns option makes the build crash. I don't really know a good workaround. Should I close this PR or do you have any ideas ? Thank you !

[endiliey]

polyfill features that are missing to ie11 only without importing whole corejs ?