Update __exportStar helper to skip default and __esModule members

[Wesley Wigham (weswigham)]

Fixes #37234

[Ron Buckton (rbuckton)]

Won't __esModule always be skipped because we emit it unconditionally anyways?

[Wesley Wigham (weswigham)]

Hm, fair, yeah.

[bluelovers (bluelovers)]

i think this not a good way for avoid bug

u will see bug happen again when run e1.ts

e1.ts

export * from './e2'

export function abc()
{

}

e2.ts

export function abc()
{

}

[Wesley Wigham (weswigham)]

bluelovers (@bluelovers) We hoist an undefined member assignment so that actually works just fine (as the hoisted assignment blocks us from overwriting it with the exportStar helper). It's only default that's a little different, since we don't track default as an exported name. That may actually be a better fix - hoisting an exports.default = void 0 assignment would be a bit more inline with other exports, at least.

[Wesley Wigham (weswigham)]

Ron Buckton (@rbuckton) you think we should hoist an assignment to default, rather than change the helper?

[bluelovers (bluelovers)]

every named export after export * if that name exists in import target

will Cannot set property xxx of #<Object> which has only a getter

every export after export * should overwrite exists

[Wesley Wigham (weswigham)]

Except it doesn't, because

export * from './e2'

export function abc()
{

}

compiles to

exports.abc = void 0;
__exportStar(require("./e2"), exports);
function abc() {
}
exports.abc = abc;

and that hoisted exports.abc = void 0 assignment prevents the __exportStar helper from overwriting that member.

[bluelovers (bluelovers)]

oh, i see

it already fix in current next version

my version still at 20200228

[Ron Buckton (rbuckton)]

Wesley Wigham (@weswigham) no, I don't think we should hoist an assignment for default, as that is observable on the module object in CommonJS (and wouldn't be observable on the module namespace object in a true ES module).

I think the behavior of the helper to explicitly skip default is correct and consistent with the spec behavior: https://tc39.es/ecma262/#sec-getexportednames (Step 9.c.i.)

[bluelovers (bluelovers)]

how about make a exports.default = void 0;
when has export default

[Wesley Wigham (weswigham)]

Ron Buckton (@rbuckton) ?