$imports export can break repeated uses of export * from <module>

[robertknight]

This plugin adds an $import export to every module it processes. That can break code which relies on being able to re-export everything from a collection of modules using export * from <module> multiple times. For example:

// index.js
export * from './module-a'
export * from './module-b'

If module-a and module-b are both processed by this plugin, Babel will complain of a duplicate $imports identifier here.

A workaround might be to generate a unique name for the $imports symbol in each file, and then provide a helper function to access it. Alternatively some kind of convention like taking the basename of the file could be used.

I found this while testing the plugin with Gutenberg.

[robertknight]

Some other ideas:

1. Rewrite export * from "module" as export { <specifiers> } from "module" where < specifiers > are automatically determined the exports of "module"
2. Define an alternative, non-export way of exposing a modules $imports object. For example by adding a function call at the end of the file which registers it in some global map that a test can then query.

I think I prefer (2) here because it doesn't require accessing any other files. We would need to find some key to use for the $imports object though, ideally the same as the one that would be used for import or require calls.