Duplicate exports from the same source file are incorrectly excluded

[timfish]

If a module has multiple exports with the same name, these do not get exported. This can occur when export * is used to merge exports from multiple files. However, if a duplicate named export actually comes from the same source file, it should be retained.

A simple example:
a.mjs

export const val = 1;

b.mjs

export * from './a.mjs';

c.mjs

export * from './a.mjs';
export * from './b.mjs';

When run in Node, c.mjs has a single export named val.
When running through import-in-the-middle there is no export.

This issues currently affects for the following libraries:

• svelte
• drizzle-orm

Using these libraries when they have been wrapped by import-in-the-middle results in errors like:

• ReferenceError: X is not defined
• The requested module 'M' does not provide an export named 'X'