Support new `export * as ns` syntax

Feature request

There is new export syntax: export * as ns (stage 4).

https://github.com/tc39/proposal-export-ns-from

export * as ns from './test';

Currently this will error:

ERROR in ./src/proxy.js 1:9
Module parse failed: Unexpected token (1:9)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
> export * as ns from './test';
 @ ./src/index.js 1:0-29 2:12-14

FWIW, TypeScript recently added support for this: https://devblogs.microsoft.com/typescript/announcing-typescript-3-8/#export-star-as-namespace-syntax

What is the expected behavior?

What is motivation or use case for adding/changing the behavior?

How should this be implemented in your opinion?

Are you willing to work on this yourself? yes

[jun-sheaf]

A current workaround is to use Babel and its @babel/plugin-proposal-export-namespace-from plugin. You can set is up like so for bare-minimum babel:

For dependencies,

npm i -D @babel/core babel-loader @babel/plugin-proposal-export-namespace-from

In your webpack.config.js,

...
{
    test: /\.tsx?$/,
    use: [{
         loader: "babel-loader", // This should be the last loader of course
         options: {
              plugins: ["@babel/plugin-proposal-export-namespace-from"]
         }
    }, ...other loaders]
}
...

[appzuka]

Is this the same issue as https://github.com/TypeStrong/ts-loader/issues/1121?

If you use a module target lower than es2020 then typescript will transpile the new export * syntax down to a version webpack can understand.