[RFC] Remove typings for `@material-ui/core/es`

[eps1lon]

Disclaimer: This can only break builds for typescript users. VSCode JS users will loose some intellisense.

We're currently duplicating our type declarations for the /es build folder to support
type definitions for imports like import Button from '@material-ui/core/es/Button'.

I propose the get rid of this duplication to reduce download size of this package and improve the typescript experience for codesandbox. Codesandbox is currently bailing out of type acquisition because it detects to many type declaration files.

This does not mean that explicit imports from the /es build are not supported anymore. Typescript/VSCode users would only have to add the following path alias to their tsconfig/jsconfig:

"paths": {
  "@material-ui/core/es*": ["@material-ui/core/*"]
}

I'm aware that this is not working for react-scripts@2.x. See facebook/create-react-app#5645

I would file this under "advanced build scenarios". The /es build does not support our supported platforms anyway and likely requires additional transpilation steps depending on your target. It shouldn't be part of your import paths and rather aliased (and processed) in your build pipeline.

/cc @mui-org/core-contributors

[oliviertassinari]

I'm happy with this change 👍, it's already for advanced users: https://material-ui.com/guides/minimizing-bundle-size/#ecmascript. I would expect few users relying on /es.

[joshwooding]

Hopefully this change will increase the accuracy of IntelliJ choosing the correct import to auto complete. I’m happy too 👍