Weird handling of `import * as ns from "..."; export { ns }`

[nicolo-ribaudo]

In ParseModule we have some logic to make sure that import { foo } from "mod"; export { foo } is equivalent to export { foo } from "mod"

See Table 59 for how export { foo } from "mod" is represented: ExportEntry Record { [[ExportName]]: "foo", [[ModuleRequest]]: "mod", [[ImportName]]: "foo", [[LocalName]]: null }. Step 10.a.ii.3 makes sure that we build the same ExportEntry Record for import { foo } from "mod"; export { foo }.

For some reason, we are not doing the same in step 10.a.ii.2, which handles import * as foo from "mod"; export { foo }. export * as foo from "mod" is represented as ExportEntry Record { [[ExportName]]: "foo", [[ModuleRequest]]: "mod", [[ImportName]]: ~all~, [[LocalName]]: null }, but in the import+export case we'll keep it as ExportEntry Record { [[ExportName]]: "foo", [[ModuleRequest]]: null, [[ImportName]]: null, [[LocalName]]: "foo" }, as if we were exporting a local binding.

I am not sure yet whether this has any observable consequence or not. export * as ns from "mod" was introduced after ES6 (in #1174, by @spectranaut), and it seems like this was never brought up.

I'm manly opening this issue as a reminder for myself to check if it matters or not.

[nicolo-ribaudo]

Ok I believe an observable difference (but I didn't check yet) might be that this code works:

// entrypoint
import { foo } from "./join.js";

// join.js
export * from "./left.js";
export * from "./right.js";

// left.js
export { foo } from "./mod.js";

// right.js
import { foo } from "./mod.js";
export { foo };

// mod.js
export const foo = 2;

This code works:

// entrypoint
import { foo } from "./join.js";

// join.js
export * from "./left.js";
export * from "./right.js";

// left.js
export * as foo from "./mod.js";

// right.js
export * as foo from "./mod.js";

// mod.js
export const x = 2;

But this throws:

// entrypoint
import { foo } from "./join.js";

// join.js
export * from "./left.js";
export * from "./right.js";

// left.js
export * as foo from "./mod.js";

// right.js
import * as foo from "./mod.js";
export { foo };

// mod.js
export const x = 2;

[nicolo-ribaudo]

It seems like browsers disagree about when a namespace binding is ambiguous or not.

I'll present something in plenary, to decide whether we want to:

• keep the spec as-is
• make it always ambiguous
• make neither case ambiguous

All these options will require implementation changes anyway.