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LibJS: Update spec comments in Array.fromAsync

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This was a normative change in the Array.fromAsync spec which we already
implemented :^). See:

https://github.com/tc39/proposal-array-from-async/commit/689d0d

I've left an existing FIXME in there for some other bug which we have
which is causing some test262 test cases to fail.
This commit is contained in:
Shannon Booth 2023-12-24 11:26:00 +13:00 • committed by Tim Flynn
parent 41941aeb10
commit 95e9c89a15
1 changed files with 16 additions and 28 deletions
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44
Userland/Libraries/LibJS/Runtime/ArrayConstructor.cpp
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@ -383,50 +383,38 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayConstructor::from_async)
// 2. Let Pk be ! ToString(𝔽(k)). // 2. Let Pk be ! ToString(𝔽(k)).
auto property_key = PropertyKey { k }; auto property_key = PropertyKey { k };
// FIXME: Spec bug: https://github.com/tc39/proposal-array-from-async/issues/33. // FIXME: There seems to be a bug here where we are not respecting array mutation. After resolving the first entry, the
// Implementing the following would cause an infinite loop. // iterator should also take into account any other changes which are made to async_items (which does not seem to
// // be happening).
// 3. Let next be ? Await(IteratorStep(iteratorRecord)).
// 4. If next is false, then
// a. Perform ? Set(A, "length", 𝔽(k), true).
// b. Return Completion Record { [[Type]]: return, [[Value]]: A, [[Target]]: empty }.
// 5. Let nextValue be ? IteratorValue(next).
//
// Below implements the suggested fix: https://github.com/tc39/proposal-array-from-async/issues/33#issuecomment-1279296963
//
// There also seems to be a second issue here where we are not respecting array mutation. After resolving the first entry, the
// iterator should also take into account any other changes which are made to async_items (which does not seem to be happening).
// Let nextResult be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]]). // 3. Let nextResult be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]]).
auto next_result = TRY(JS::call(vm, iterator_record->next_method, iterator_record->iterator)); auto next_result = TRY(JS::call(vm, iterator_record->next_method, iterator_record->iterator));
// Set nextResult to ? Await(nextResult). // 4. Set nextResult to ? Await(nextResult).
next_result = TRY(await(vm, next_result)); next_result = TRY(await(vm, next_result));
// If nextResult is not an Object, throw a TypeError exception. // 5. If nextResult is not an Object, throw a TypeError exception.
if (!next_result.is_object()) if (!next_result.is_object())
return vm.throw_completion<TypeError>(ErrorType::IterableNextBadReturn); return vm.throw_completion<TypeError>(ErrorType::IterableNextBadReturn);
// Let done be ? IteratorComplete(nextResult). // 6. Let done be ? IteratorComplete(nextResult).
auto done = TRY(JS::iterator_complete(vm, next_result.as_object())); auto done = TRY(JS::iterator_complete(vm, next_result.as_object()));
// If done is true, // 7. If done is true,
if (done) { if (done) {
// Perform ? Set(A, "length", 𝔽(k), true). // a. Perform ? Set(A, "length", 𝔽(k), true).
TRY(array->set(vm.names.length, Value(k), Object::ShouldThrowExceptions::Yes)); TRY(array->set(vm.names.length, Value(k), Object::ShouldThrowExceptions::Yes));
// Return Completion Record { [[Type]]: return, [[Value]]: A, [[Target]]: empty }. // b. Return Completion Record { [[Type]]: return, [[Value]]: A, [[Target]]: empty }.
return Completion { Completion::Type::Return, array, {} }; return Completion { Completion::Type::Return, array, {} };
} }
// Let nextValue be ? IteratorValue(nextResult). // 8. Let nextValue be ? IteratorValue(nextResult).
auto next_value = TRY(iterator_value(vm, next_result.as_object())); auto next_value = TRY(iterator_value(vm, next_result.as_object()));
// (spec deviation ends here)
Value mapped_value; Value mapped_value;
// 6. If mapping is true, then // 9. If mapping is true, then
if (mapping) { if (mapping) {
// a. Let mappedValue be Call(mapfn, thisArg, « nextValue, 𝔽(k) »). // a. Let mappedValue be Call(mapfn, thisArg, « nextValue, 𝔽(k) »).
auto mapped_value_or_error = JS::call(vm, mapfn, this_arg, next_value, Value(k)); auto mapped_value_or_error = JS::call(vm, mapfn, this_arg, next_value, Value(k));
@ -448,19 +436,19 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayConstructor::from_async)
mapped_value = mapped_value_or_error.value(); mapped_value = mapped_value_or_error.value();
} }
// 7. Else, let mappedValue be nextValue. // 10. Else, let mappedValue be nextValue.
else { else {
mapped_value = next_value; mapped_value = next_value;
} }
// 8. Let defineStatus be CreateDataPropertyOrThrow(A, Pk, mappedValue). // 11. Let defineStatus be CreateDataPropertyOrThrow(A, Pk, mappedValue).
auto define_status = array->create_data_property_or_throw(property_key, mapped_value); auto define_status = array->create_data_property_or_throw(property_key, mapped_value);
// 9. If defineStatus is an abrupt completion, return ? AsyncIteratorClose(iteratorRecord, defineStatus). // 12. If defineStatus is an abrupt completion, return ? AsyncIteratorClose(iteratorRecord, defineStatus).
if (define_status.is_error()) if (define_status.is_error())
return *TRY(iterator_close(vm, *iterator_record, define_status.release_error())); return *TRY(iterator_close(vm, *iterator_record, define_status.release_error()));
// 10. Set k to k + 1. // 13. Set k to k + 1.
} }
} }
// k. Else, // k. Else,