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LibJS: Implement proper Iterator records

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Instead of using plain objects as Iterator records, causes confusion
about the object itself actually being its [[Iterator]] slot, and
requires non-standard type conversion shenanigans fpr the [[NextValue]]
and [[Done]] internal slots,  implement a proper Iterator record struct
and use it throughout.

Also annotate the remaining Iterator AOs with spec comments while we're
here.
This commit is contained in:
Linus Groh 2022-01-09 19:12:24 +01:00
parent e141f1e976
commit 09a11fa6ea
17 changed files with 337 additions and 209 deletions
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139
Userland/Libraries/LibJS/Runtime/IteratorOperations.cpp
View file

@ -1,5 +1,6 @@
/*
* Copyright (c) 2020, Matthew Olsson <mattco@serenityos.org>
* Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -15,53 +16,81 @@
namespace JS {
// 7.4.1 GetIterator ( obj [ , hint [ , method ] ] ), https://tc39.es/ecma262/#sec-getiterator
ThrowCompletionOr<Object*> get_iterator(GlobalObject& global_object, Value value, IteratorHint hint, Optional<Value> method)
ThrowCompletionOr<Iterator> get_iterator(GlobalObject& global_object, Value value, IteratorHint hint, Optional<Value> method)
{
auto& vm = global_object.vm();
// 1. If hint is not present, set hint to sync.
// 2. If method is not present, then
if (!method.has_value()) {
// a. If hint is async, then
if (hint == IteratorHint::Async) {
// i. Set method to ? GetMethod(obj, @@asyncIterator).
auto* async_method = TRY(value.get_method(global_object, *vm.well_known_symbol_async_iterator()));
// ii. If method is undefined, then
if (async_method == nullptr) {
// 1. Let syncMethod be ? GetMethod(obj, @@iterator).
auto* sync_method = TRY(value.get_method(global_object, *vm.well_known_symbol_iterator()));
auto* sync_iterator_record = TRY(get_iterator(global_object, value, IteratorHint::Sync, sync_method));
return TRY(create_async_from_sync_iterator(global_object, *sync_iterator_record));
// 2. Let syncIteratorRecord be ? GetIterator(obj, sync, syncMethod).
auto sync_iterator_record = TRY(get_iterator(global_object, value, IteratorHint::Sync, sync_method));
// 3. Return ! CreateAsyncFromSyncIterator(syncIteratorRecord).
return MUST(create_async_from_sync_iterator(global_object, sync_iterator_record));
}
method = Value(async_method);
} else {
}
// b. Otherwise, set method to ? GetMethod(obj, @@iterator).
else {
method = TRY(value.get_method(global_object, *vm.well_known_symbol_iterator()));
}
}
// NOTE: Additional type check to produce a better error message than Call().
if (!method->is_function())
return vm.throw_completion<TypeError>(global_object, ErrorType::NotIterable, value.to_string_without_side_effects());
auto iterator = TRY(vm.call(method->as_function(), value));
// 3. Let iterator be ? Call(method, obj).
auto iterator = TRY(call(global_object, *method, value));
// 4. If Type(iterator) is not Object, throw a TypeError exception.
if (!iterator.is_object())
return vm.throw_completion<TypeError>(global_object, ErrorType::NotIterable, value.to_string_without_side_effects());
return &iterator.as_object();
// 5. Let nextMethod be ? GetV(iterator, "next").
auto next_method = TRY(iterator.get(global_object, vm.names.next));
// 6. Let iteratorRecord be the Record { [[Iterator]]: iterator, [[NextMethod]]: nextMethod, [[Done]]: false }.
auto iterator_record = Iterator { .iterator = &iterator.as_object(), .next_method = next_method, .done = false };
// 7. Return iteratorRecord.
return iterator_record;
}
// 7.4.2 IteratorNext ( iteratorRecord [ , value ] ), https://tc39.es/ecma262/#sec-iteratornext
ThrowCompletionOr<Object*> iterator_next(Object& iterator, Optional<Value> value)
ThrowCompletionOr<Object*> iterator_next(GlobalObject& global_object, Iterator const& iterator_record, Optional<Value> value)
{
// FIXME: Implement using iterator records, not ordinary objects
auto& vm = iterator.vm();
auto& global_object = iterator.global_object();
auto next_method = TRY(iterator.get(vm.names.next));
if (!next_method.is_function())
return vm.throw_completion<TypeError>(global_object, ErrorType::IterableNextNotAFunction);
auto& vm = global_object.vm();
Value result;
if (!value.has_value())
result = TRY(vm.call(next_method.as_function(), &iterator));
else
result = TRY(vm.call(next_method.as_function(), &iterator, *value));
// 1. If value is not present, then
if (!value.has_value()) {
// a. Let result be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]]).
result = TRY(call(global_object, iterator_record.next_method, iterator_record.iterator));
} else {
// a. Let result be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]], « value »).
result = TRY(call(global_object, iterator_record.next_method, iterator_record.iterator, *value));
}
// 3. If Type(result) is not Object, throw a TypeError exception.
if (!result.is_object())
return vm.throw_completion<TypeError>(global_object, ErrorType::IterableNextBadReturn);
// 4. Return result.
return &result.as_object();
}
@ -84,53 +113,60 @@ ThrowCompletionOr<Value> iterator_value(GlobalObject& global_object, Object& ite
}
// 7.4.5 IteratorStep ( iteratorRecord ), https://tc39.es/ecma262/#sec-iteratorstep
ThrowCompletionOr<Object*> iterator_step(GlobalObject& global_object, Object& iterator)
ThrowCompletionOr<Object*> iterator_step(GlobalObject& global_object, Iterator const& iterator_record)
{
auto* result = TRY(iterator_next(iterator));
// 1. Let result be ? IteratorNext(iteratorRecord).
auto* result = TRY(iterator_next(global_object, iterator_record));
// 2. Let done be ? IteratorComplete(result).
auto done = TRY(iterator_complete(global_object, *result));
// 3. If done is true, return false.
if (done)
return nullptr;
// 4. Return result.
return result;
}
// 7.4.6 IteratorClose ( iteratorRecord, completion ), https://tc39.es/ecma262/#sec-iteratorclose
// 7.4.8 AsyncIteratorClose ( iteratorRecord, completion ), https://tc39.es/ecma262/#sec-asynciteratorclose
// NOTE: These only differ in that async awaits the inner value after the call.
static Completion iterator_close_(Object& iterator, Completion completion, IteratorHint iterator_hint)
static Completion iterator_close_impl(GlobalObject& global_object, Iterator const& iterator_record, Completion completion, IteratorHint iterator_hint)
{
auto& vm = iterator.vm();
auto& global_object = iterator.global_object();
auto& vm = global_object.vm();
// 1. Assert: Type(iteratorRecord.[[Iterator]]) is Object.
// 2. Let iterator be iteratorRecord.[[Iterator]].
auto* iterator = iterator_record.iterator;
// The callers of iterator_close() are often in an exceptional state.
// Temporarily clear that exception for invocation(s) to Call.
TemporaryClearException clear_exception(vm);
// 3. Let innerResult be GetMethod(iterator, "return").
auto inner_result_or_error = Value(&iterator).get_method(global_object, vm.names.return_);
Value inner_result;
auto inner_result = ThrowCompletionOr<Value> { js_undefined() };
auto get_method_result = Value(iterator).get_method(global_object, vm.names.return_);
if (get_method_result.is_error())
inner_result = get_method_result.release_error();
// 4. If innerResult.[[Type]] is normal, then
if (!inner_result_or_error.is_error()) {
if (!inner_result.is_error()) {
// a. Let return be innerResult.[[Value]].
auto* return_method = inner_result_or_error.release_value();
auto* return_method = get_method_result.value();
// b. If return is undefined, return Completion(completion).
if (!return_method)
return completion;
// c. Set innerResult to Call(return, iterator).
auto result_or_error = vm.call(*return_method, &iterator);
if (result_or_error.is_error()) {
inner_result_or_error = result_or_error.release_error();
} else {
inner_result = result_or_error.release_value();
// Note: If this is AsyncIteratorClose perform one extra step.
if (iterator_hint == IteratorHint::Async) {
// d. If innerResult.[[Type]] is normal, set innerResult to Await(innerResult.[[Value]]).
inner_result = TRY(await(global_object, inner_result));
}
inner_result = call(global_object, return_method, iterator);
// Note: If this is AsyncIteratorClose perform one extra step.
if (iterator_hint == IteratorHint::Async && !inner_result.is_error()) {
// d. If innerResult.[[Type]] is normal, set innerResult to Await(innerResult.[[Value]]).
inner_result = await(global_object, inner_result.value());
}
}
@ -139,11 +175,11 @@ static Completion iterator_close_(Object& iterator, Completion completion, Itera
return completion;
// 6. If innerResult.[[Type]] is throw, return Completion(innerResult).
if (inner_result_or_error.is_error())
return inner_result_or_error.release_error();
if (inner_result.is_throw_completion())
return inner_result;
// 7. If Type(innerResult.[[Value]]) is not Object, throw a TypeError exception.
if (!inner_result.is_object())
if (!inner_result.value().is_object())
return vm.throw_completion<TypeError>(global_object, ErrorType::IterableReturnBadReturn);
// 8. Return Completion(completion).
@ -151,24 +187,32 @@ static Completion iterator_close_(Object& iterator, Completion completion, Itera
}
// 7.4.6 IteratorClose ( iteratorRecord, completion ), https://tc39.es/ecma262/#sec-iteratorclose
Completion iterator_close(Object& iterator, Completion completion)
Completion iterator_close(GlobalObject& global_object, Iterator const& iterator_record, Completion completion)
{
return iterator_close_(iterator, move(completion), IteratorHint::Sync);
return iterator_close_impl(global_object, iterator_record, move(completion), IteratorHint::Sync);
}
// 7.4.8 AsyncIteratorClose ( iteratorRecord, completion ), https://tc39.es/ecma262/#sec-asynciteratorclose
Completion async_iterator_close(Object& iterator, Completion completion)
Completion async_iterator_close(GlobalObject& global_object, Iterator const& iterator_record, Completion completion)
{
return iterator_close_(iterator, move(completion), IteratorHint::Async);
return iterator_close_impl(global_object, iterator_record, move(completion), IteratorHint::Async);
}
// 7.4.9 CreateIterResultObject ( value, done ), https://tc39.es/ecma262/#sec-createiterresultobject
Object* create_iterator_result_object(GlobalObject& global_object, Value value, bool done)
{
auto& vm = global_object.vm();
// 1. Let obj be ! OrdinaryObjectCreate(%Object.prototype%).
auto* object = Object::create(global_object, global_object.object_prototype());
// 2. Perform ! CreateDataPropertyOrThrow(obj, "value", value).
MUST(object->create_data_property_or_throw(vm.names.value, value));
// 3. Perform ! CreateDataPropertyOrThrow(obj, "done", done).
MUST(object->create_data_property_or_throw(vm.names.done, Value(done)));
// 4. Return obj.
return object;
}
@ -188,19 +232,20 @@ ThrowCompletionOr<MarkedValueList> iterable_to_list(GlobalObject& global_object,
return { move(values) };
}
// Non-standard
Completion get_iterator_values(GlobalObject& global_object, Value iterable, IteratorValueCallback callback, Optional<Value> method)
{
auto* iterator = TRY(get_iterator(global_object, iterable, IteratorHint::Sync, move(method)));
auto iterator_record = TRY(get_iterator(global_object, iterable, IteratorHint::Sync, move(method)));
while (true) {
auto* next_object = TRY(iterator_step(global_object, *iterator));
auto* next_object = TRY(iterator_step(global_object, iterator_record));
if (!next_object)
return {};
auto next_value = TRY(iterator_value(global_object, *next_object));
if (auto completion = callback(next_value); completion.has_value())
return iterator_close(*iterator, completion.release_value());
return iterator_close(global_object, iterator_record, completion.release_value());
}
}