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LibJS: Implement Iterator.from and the WrapForValidIteratorPrototype

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Iterator.from creates an Iterator from either an existing iterator or
an iterator-like object. In the latter case, it sets the prototype of
the returned iterator to WrapForValidIteratorPrototype to wrap around
the iterator-like object's iteration methods.
This commit is contained in:
Timothy Flynn 2023-06-24 11:27:30 -04:00 • committed by Andreas Kling
parent 5736b53013
commit d9d245faa7
Notes: sideshowbarker 2024-07-18 03:35:30 +09:00
11 changed files with 299 additions and 0 deletions
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34
Userland/Libraries/LibJS/Runtime/IteratorConstructor.cpp
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@ -29,6 +29,9 @@ ThrowCompletionOr<void> IteratorConstructor::initialize(Realm& realm)
// 3.1.1.2.1 Iterator.prototype, https://tc39.es/proposal-iterator-helpers/#sec-iterator.prototype
define_direct_property(vm.names.prototype, realm.intrinsics().iterator_prototype(), 0);
u8 attr = Attribute::Writable | Attribute::Configurable;
define_native_function(realm, vm.names.from, from, 1, attr);
define_direct_property(vm.names.length, Value(0), Attribute::Configurable);
return {};
@ -56,4 +59,35 @@ ThrowCompletionOr<NonnullGCPtr<Object>> IteratorConstructor::construct(FunctionO
return TRY(ordinary_create_from_constructor<Iterator>(vm, new_target, &Intrinsics::iterator_prototype));
}
// 3.1.1.2.2 Iterator.from ( O ), https://tc39.es/proposal-iterator-helpers/#sec-iterator.from
JS_DEFINE_NATIVE_FUNCTION(IteratorConstructor::from)
{
auto& realm = *vm.current_realm();
auto object = vm.argument(0);
// 1. If O is a String, set O to ! ToObject(O).
if (object.is_string())
object = MUST_OR_THROW_OOM(object.to_object(vm));
// 2. Let iteratorRecord be ? GetIteratorFlattenable(O).
auto iterator_record = TRY(get_iterator_flattenable(vm, object));
// 3. Let hasInstance be ? OrdinaryHasInstance(%Iterator%, iteratorRecord.[[Iterator]]).
auto has_instance = TRY(ordinary_has_instance(vm, iterator_record.iterator, realm.intrinsics().iterator_constructor()));
// 4. If hasInstance is true, then
if (has_instance.is_boolean() && has_instance.as_bool()) {
// a. Return iteratorRecord.[[Iterator]].
return iterator_record.iterator;
}
// 5. Let wrapper be OrdinaryObjectCreate(%WrapForValidIteratorPrototype%, « [[Iterated]] »).
// 6. Set wrapper.[[Iterated]] to iteratorRecord.
auto wrapper = MUST_OR_THROW_OOM(Iterator::create(realm, realm.intrinsics().wrap_for_valid_iterator_prototype(), move(iterator_record)));
// 7. Return wrapper.
return wrapper;
}
}