What kind of change does this PR introduce?

🚧 WIP...

improve output for external module of library.type: module

Before:

import * as __WEBPACK_EXTERNAL_MODULE_external from 'external'
__WEBPACK_EXTERNAL_MODULE_external.foo;

This PR:

import { foo } from 'external'
foo;

ExternalModule is imported though InitFragment, which will insert a namespace import, but user may want to keep the code as is

// input
import { foo } from 'external'
foo;
// output
import * as __WEBPACK_EXTERNAL_MODULE_external from 'external'
__WEBPACK_EXTERNAL_MODULE_external.foo;

As we know the exportsInfo, we can use them to improve the output.

If exportsInfo.getUsedExports() equals:

• true: used unknown exports from external module, fallback to namespace import like before
• Set<string>: we know exactly used exports from external module, render them, we should also insert the exported specifier into ConcatenationScope.allUsedNames to avoid conflicts

Did you add tests for your changes?

WIP...

Does this PR introduce a breaking change?

No

What needs to be documented once your changes are merged?