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/*
* Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/PromiseCapability.h>
namespace JS {
// 27.2.1.5 NewPromiseCapability ( C ), https://tc39.es/ecma262/#sec-newpromisecapability
ThrowCompletionOr<PromiseCapability> new_promise_capability(VM& vm, Value constructor)
{
auto& realm = *vm.current_realm();
// 1. If IsConstructor(C) is false, throw a TypeError exception.
if (!constructor.is_constructor())
return vm.throw_completion<TypeError>(ErrorType::NotAConstructor, constructor.to_string_without_side_effects());
// 2. NOTE: C is assumed to be a constructor function that supports the parameter conventions of the Promise constructor (see 27.2.3.1).
// 3. Let promiseCapability be the PromiseCapability Record { [[Promise]]: undefined, [[Resolve]]: undefined, [[Reject]]: undefined }.
// FIXME: This should not be stack-allocated, the executor function below can be captured and outlive it!
// See https://discord.com/channels/830522505605283862/886211697843531866/900081190621569154 for some discussion.
struct {
Value resolve { js_undefined() };
Value reject { js_undefined() };
} promise_capability_functions;
// 4. Let executorClosure be a new Abstract Closure with parameters (resolve, reject) that captures promiseCapability and performs the following steps when called:
auto executor_closure = [&promise_capability_functions](auto& vm) -> ThrowCompletionOr<Value> {
auto resolve = vm.argument(0);
auto reject = vm.argument(1);
// No idea what other engines say here.
// a. If promiseCapability.[[Resolve]] is not undefined, throw a TypeError exception.
if (!promise_capability_functions.resolve.is_undefined())
return vm.template throw_completion<TypeError>(ErrorType::GetCapabilitiesExecutorCalledMultipleTimes);
// b. If promiseCapability.[[Reject]] is not undefined, throw a TypeError exception.
if (!promise_capability_functions.reject.is_undefined())
return vm.template throw_completion<TypeError>(ErrorType::GetCapabilitiesExecutorCalledMultipleTimes);
// c. Set promiseCapability.[[Resolve]] to resolve.
promise_capability_functions.resolve = resolve;
// d. Set promiseCapability.[[Reject]] to reject.
promise_capability_functions.reject = reject;
// e. Return undefined.
return js_undefined();
};
// 5. Let executor be CreateBuiltinFunction(executorClosure, 2, "", « »).
auto* executor = NativeFunction::create(realm, move(executor_closure), 2, "");
// 6. Let promise be ? Construct(C, « executor »).
auto* promise = TRY(construct(vm, constructor.as_function(), executor));
// 7. If IsCallable(promiseCapability.[[Resolve]]) is false, throw a TypeError exception.
if (!promise_capability_functions.resolve.is_function())
return vm.throw_completion<TypeError>(ErrorType::NotAFunction, promise_capability_functions.resolve.to_string_without_side_effects());
// 8. If IsCallable(promiseCapability.[[Reject]]) is false, throw a TypeError exception.
if (!promise_capability_functions.reject.is_function())
return vm.throw_completion<TypeError>(ErrorType::NotAFunction, promise_capability_functions.reject.to_string_without_side_effects());
// 9. Set promiseCapability.[[Promise]] to promise.
// 10. Return promiseCapability.
return PromiseCapability {
promise,
&promise_capability_functions.resolve.as_function(),
&promise_capability_functions.reject.as_function(),
};
}
}
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