LibJS: Add spec comments to WeakMapConstructor

Userland/Libraries/LibJS/Runtime/WeakMapConstructor.cpp

@@ -35,35 +35,45 @@ ThrowCompletionOr<void> WeakMapConstructor::initialize(Realm& realm)
 ThrowCompletionOr<Value> WeakMapConstructor::call()
 {
  auto& vm = this->vm();
+
+ // 1. If NewTarget is undefined, throw a TypeError exception.
  return vm.throw_completion<TypeError>(ErrorType::ConstructorWithoutNew, vm.names.WeakMap);
 }
 
 // 24.3.1.1 WeakMap ( [ iterable ] ), https://tc39.es/ecma262/#sec-weakmap-iterable
 ThrowCompletionOr<NonnullGCPtr<Object>> WeakMapConstructor::construct(FunctionObject& new_target)
 {
  auto& vm = this->vm();
+ auto iterable = vm.argument(0);
+
+ // 2. Let map be ? OrdinaryCreateFromConstructor(NewTarget, "%WeakMap.prototype%", « [[WeakMapData]] »).
+ // 3. Set map.[[WeakMapData]] to a new empty List.
+ auto map = TRY(ordinary_create_from_constructor<WeakMap>(vm, new_target, &Intrinsics::weak_map_prototype));
 
- auto weak_map = TRY(ordinary_create_from_constructor<WeakMap>(vm, new_target, &Intrinsics::weak_map_prototype));
+ // 4. If iterable is either undefined or null, return map.
+ if (iterable.is_nullish())
+ return map;
 
- if (vm.argument(0).is_nullish())
-  return weak_map;
+ // 5. Let adder be ? Get(map, "set").
+ auto adder = TRY(map->get(vm.names.set));
 
- auto adder = TRY(weak_map->get(vm.names.set));
+ // 6. If IsCallable(adder) is false, throw a TypeError exception.
  if (!adder.is_function())
  return vm.throw_completion<TypeError>(ErrorType::NotAFunction, "'set' property of WeakMap");
 
- (void)TRY(get_iterator_values(vm, vm.argument(0), [&](Value iterator_value) -> Optional<Completion> {
+ // 7. Return ? AddEntriesFromIterable(map, iterable, adder).
+ (void)TRY(get_iterator_values(vm, iterable, [&](Value iterator_value) -> Optional<Completion> {
  if (!iterator_value.is_object())
  return vm.throw_completion<TypeError>(ErrorType::NotAnObject, DeprecatedString::formatted("Iterator value {}", TRY_OR_THROW_OOM(vm, iterator_value.to_string_without_side_effects())));
 
  auto key = TRY(iterator_value.as_object().get(0));
  auto value = TRY(iterator_value.as_object().get(1));
- TRY(JS::call(vm, adder.as_function(), weak_map, key, value));
+ TRY(JS::call(vm, adder.as_function(), map, key, value));
 
  return {};
  }));
 
- return weak_map;
+ return map;
 }
 
 }