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LibJS: Implement Array.fromAsync

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Shannon Booth 2023-07-15 22:37:22 +12:00 • committed by Linus Groh
parent 80b48b708f
commit fe4f2923f8
3 changed files with 246 additions and 0 deletions
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244
Userland/Libraries/LibJS/Runtime/ArrayConstructor.cpp
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@ -1,6 +1,7 @@
/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2023, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2023, Shannon Booth <shannon@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -9,9 +10,14 @@
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/ArrayConstructor.h>
#include <LibJS/Runtime/AsyncFromSyncIteratorPrototype.h>
#include <LibJS/Runtime/Completion.h>
#include <LibJS/Runtime/ECMAScriptFunctionObject.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/IteratorOperations.h>
#include <LibJS/Runtime/PromiseCapability.h>
#include <LibJS/Runtime/PromiseConstructor.h>
#include <LibJS/Runtime/Shape.h>
namespace JS {
@ -31,6 +37,7 @@ ThrowCompletionOr<void> ArrayConstructor::initialize(Realm& realm)
u8 attr = Attribute::Writable | Attribute::Configurable;
define_native_function(realm, vm.names.from, from, 1, attr);
define_native_function(realm, vm.names.fromAsync, from_async, 1, attr);
define_native_function(realm, vm.names.isArray, is_array, 1, attr);
define_native_function(realm, vm.names.of, of, 0, attr);
@ -286,6 +293,243 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayConstructor::from)
return array;
}
// 2.1.1.1 Array.fromAsync ( asyncItems [ , mapfn [ , thisArg ] ] ), https://tc39.es/proposal-array-from-async/#sec-array.fromAsync
JS_DEFINE_NATIVE_FUNCTION(ArrayConstructor::from_async)
{
auto& realm = *vm.current_realm();
auto async_items = vm.argument(0);
auto mapfn = vm.argument(1);
auto this_arg = vm.argument(2);
// 1. Let C be the this value.
auto constructor = vm.this_value();
// 2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
auto promise_capability = MUST(new_promise_capability(vm, realm.intrinsics().promise_constructor()));
// 3. Let fromAsyncClosure be a new Abstract Closure with no parameters that captures C, mapfn, and thisArg and performs the following steps when called:
SafeFunction<Completion()> from_async_closure = [constructor, mapfn, this_arg, &vm, &realm, async_items]() mutable -> Completion {
bool mapping;
// a. If mapfn is undefined, let mapping be false.
if (mapfn.is_undefined()) {
mapping = false;
}
// b. Else,
else {
// i. If IsCallable(mapfn) is false, throw a TypeError exception.
if (!mapfn.is_function())
return vm.throw_completion<TypeError>(ErrorType::NotAFunction, TRY_OR_THROW_OOM(vm, mapfn.to_string_without_side_effects()));
// ii. Let mapping be true.
mapping = true;
}
// c. Let usingAsyncIterator be ? GetMethod(asyncItems, @@asyncIterator).
auto using_async_iterator = TRY(async_items.get_method(vm, vm.well_known_symbol_async_iterator()));
GCPtr<FunctionObject> using_sync_iterator;
// d. If usingAsyncIterator is undefined, then
if (!using_async_iterator) {
// i. Let usingSyncIterator be ? GetMethod(asyncItems, @@iterator).
using_sync_iterator = TRY(async_items.get_method(vm, vm.well_known_symbol_iterator()));
}
GCPtr<Object> array;
// e. If IsConstructor(C) is true, then
if (constructor.is_constructor()) {
// i. Let A be ? Construct(C).
array = TRY(JS::construct(vm, constructor.as_function()));
}
// f. Else,
else {
// i. Let A be ! ArrayCreate(0).
array = MUST(Array::create(realm, 0));
}
// g. Let iteratorRecord be undefined.
Optional<IteratorRecord> iterator_record;
// h. If usingAsyncIterator is not undefined, then
if (using_async_iterator) {
// i. Set iteratorRecord to ? GetIterator(asyncItems, async, usingAsyncIterator).
iterator_record = TRY(get_iterator(vm, async_items, IteratorHint::Async, using_async_iterator));
}
// i. Else if usingSyncIterator is not undefined, then
else if (using_sync_iterator) {
// i. Set iteratorRecord to ? CreateAsyncFromSyncIterator(GetIterator(asyncItems, sync, usingSyncIterator)).
iterator_record = create_async_from_sync_iterator(vm, TRY(get_iterator(vm, async_items, IteratorHint::Sync, using_sync_iterator)));
}
// j. If iteratorRecord is not undefined, then
if (iterator_record.has_value()) {
// i. Let k be 0.
// ii. Repeat,
for (size_t k = 0;; ++k) {
// 1. If k ≥ 2^53 - 1, then
if (k >= MAX_ARRAY_LIKE_INDEX) {
// a. Let error be ThrowCompletion(a newly created TypeError object).
auto error = vm.throw_completion<TypeError>(ErrorType::ArrayMaxSize);
// b. Return ? AsyncIteratorClose(iteratorRecord, error).
return *TRY(async_iterator_close(vm, iterator_record.value(), move(error)));
}
// 2. Let Pk be ! ToString(𝔽(k)).
auto property_key = PropertyKey { k };
// FIXME: Spec bug: https://github.com/tc39/proposal-array-from-async/issues/33.
// Implementing the following would cause an infinite loop.
//
// 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]]).
auto next_result = TRY(JS::call(vm, iterator_record->next_method, iterator_record->iterator));
// Set nextResult to ? Await(nextResult).
next_result = TRY(await(vm, next_result));
// If nextResult is not an Object, throw a TypeError exception.
if (!next_result.is_object())
return vm.throw_completion<TypeError>(ErrorType::IterableNextBadReturn);
// Let done be ? IteratorComplete(nextResult).
auto done = TRY(JS::iterator_complete(vm, next_result.as_object()));
// If done is true,
if (done) {
// Perform ? Set(A, "length", 𝔽(k), true).
TRY(array->set(vm.names.length, Value(k), Object::ShouldThrowExceptions::Yes));
// Return Completion Record { [[Type]]: return, [[Value]]: A, [[Target]]: empty }.
return Completion { Completion::Type::Return, array, {} };
}
// Let nextValue be ? IteratorValue(nextResult).
auto next_value = TRY(iterator_value(vm, next_result.as_object()));
// (spec deviation ends here)
Value mapped_value;
// 6. If mapping is true, then
if (mapping) {
// 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));
// b. IfAbruptCloseAsyncIterator(mappedValue, iteratorRecord).
if (mapped_value_or_error.is_error()) {
TRY(async_iterator_close(vm, iterator_record.value(), mapped_value_or_error));
return mapped_value_or_error;
}
// c. Set mappedValue to Await(mappedValue).
mapped_value_or_error = await(vm, mapped_value_or_error.value());
// d. IfAbruptCloseAsyncIterator(mappedValue, iteratorRecord).
if (mapped_value_or_error.is_error()) {
TRY(async_iterator_close(vm, iterator_record.value(), mapped_value_or_error));
return mapped_value_or_error;
}
mapped_value = mapped_value_or_error.value();
}
// 7. Else, let mappedValue be nextValue.
else {
mapped_value = next_value;
}
// 8. Let defineStatus be CreateDataPropertyOrThrow(A, Pk, mappedValue).
auto define_status = array->create_data_property_or_throw(property_key, mapped_value);
// 9. If defineStatus is an abrupt completion, return ? AsyncIteratorClose(iteratorRecord, defineStatus).
if (define_status.is_error())
return *TRY(iterator_close(vm, iterator_record.value(), define_status.release_error()));
// 10. Set k to k + 1.
}
}
// k. Else,
else {
// i. NOTE: asyncItems is neither an AsyncIterable nor an Iterable so assume it is an array-like object.
// ii. Let arrayLike be ! ToObject(asyncItems).
auto array_like = MUST(async_items.to_object(vm));
// iii. Let len be ? LengthOfArrayLike(arrayLike).
auto length = TRY(length_of_array_like(vm, array_like));
// iv. If IsConstructor(C) is true, then
if (constructor.is_constructor()) {
// 1. Let A be ? Construct(C, « 𝔽(len) »).
array = TRY(JS::construct(vm, constructor.as_function(), Value(length)));
}
// v. Else,
else {
// 1. Let A be ? ArrayCreate(len).
array = TRY(Array::create(realm, length));
}
// vi. Let k be 0.
// vii. Repeat, while k < len,
for (size_t k = 0; k < length; ++k) {
// 1. Let Pk be ! ToString(𝔽(k)).
auto property_key = PropertyKey { k };
// 2. Let kValue be ? Get(arrayLike, Pk).
auto k_value = TRY(array_like->get(property_key));
// 3. Set kValue to ? Await(kValue).
k_value = TRY(await(vm, k_value));
Value mapped_value;
// 4. If mapping is true, then
if (mapping) {
// a. Let mappedValue be ? Call(mapfn, thisArg, « kValue, 𝔽(k) »).
mapped_value = TRY(JS::call(vm, mapfn, this_arg, k_value, Value(k)));
// b. Set mappedValue to ? Await(mappedValue).
mapped_value = TRY(await(vm, mapped_value));
}
// 5. Else, let mappedValue be kValue.
else {
mapped_value = k_value;
}
// 6. Perform ? CreateDataPropertyOrThrow(A, Pk, mappedValue).
TRY(array->create_data_property_or_throw(property_key, mapped_value));
// 7. Set k to k + 1.
}
// viii. Perform ? Set(A, "length", 𝔽(len), true).
TRY(array->set(vm.names.length, Value(length), Object::ShouldThrowExceptions::Yes));
// ix. Return Completion Record { [[Type]]: return, [[Value]]: A, [[Target]]: empty }.
return Completion { Completion::Type::Return, array, {} };
}
};
// 4. Perform AsyncFunctionStart(promiseCapability, fromAsyncClosure).
async_function_start(vm, promise_capability, from_async_closure);
// 5. Return promiseCapability.[[Promise]].
return promise_capability->promise();
}
// 23.1.2.2 Array.isArray ( arg ), https://tc39.es/ecma262/#sec-array.isarray
JS_DEFINE_NATIVE_FUNCTION(ArrayConstructor::is_array)
{