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LibJS: Implement the Promise.withResolvers proposal

https://github.com/tc39/proposal-promise-with-resolvers
This commit is contained in:
Timothy Flynn 2023-07-12 15:28:03 -04:00 committed by Linus Groh
parent 705e96568c
commit 36d156428b
4 changed files with 87 additions and 1 deletions

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@ -405,6 +405,7 @@ namespace JS {
P(pop) \
P(pow) \
P(preventExtensions) \
P(promise) \
P(propertyIsEnumerable) \
P(prototype) \
P(proxy) \
@ -582,6 +583,7 @@ namespace JS {
P(withCalendar) \
P(withPlainDate) \
P(withPlainTime) \
P(withResolvers) \
P(withTimeZone) \
P(writable) \
P(year) \

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@ -259,6 +259,7 @@ ThrowCompletionOr<void> PromiseConstructor::initialize(Realm& realm)
define_native_function(realm, vm.names.race, race, 1, attr);
define_native_function(realm, vm.names.reject, reject, 1, attr);
define_native_function(realm, vm.names.resolve, resolve, 1, attr);
define_native_function(realm, vm.names.withResolvers, with_resolvers, 0, attr);
define_native_accessor(realm, vm.well_known_symbol_species(), symbol_species_getter, {}, Attribute::Configurable);
@ -487,4 +488,31 @@ JS_DEFINE_NATIVE_FUNCTION(PromiseConstructor::symbol_species_getter)
return vm.this_value();
}
// 1.1.1.1 Promise.withResolvers ( ), https://tc39.es/proposal-promise-with-resolvers/#sec-promise.withResolvers
JS_DEFINE_NATIVE_FUNCTION(PromiseConstructor::with_resolvers)
{
auto& realm = *vm.current_realm();
// 1. Let C be the this value.
auto constructor = vm.this_value();
// 2. Let promiseCapability be ? NewPromiseCapability(C).
auto promise_capability = TRY(new_promise_capability(vm, constructor));
// 3. Let obj be OrdinaryObjectCreate(%Object.prototype%).
auto object = Object::create(realm, realm.intrinsics().object_prototype());
// 4. Perform ! CreateDataPropertyOrThrow(obj, "promise", promiseCapability.[[Promise]]).
MUST(object->create_data_property_or_throw(vm.names.promise, promise_capability->promise()));
// 5. Perform ! CreateDataPropertyOrThrow(obj, "resolve", promiseCapability.[[Resolve]]).
MUST(object->create_data_property_or_throw(vm.names.resolve, promise_capability->resolve()));
// 6. Perform ! CreateDataPropertyOrThrow(obj, "reject", promiseCapability.[[Reject]]).
MUST(object->create_data_property_or_throw(vm.names.reject, promise_capability->reject()));
// 7. Return obj.
return object;
}
}

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@ -31,8 +31,8 @@ private:
JS_DECLARE_NATIVE_FUNCTION(race);
JS_DECLARE_NATIVE_FUNCTION(reject);
JS_DECLARE_NATIVE_FUNCTION(resolve);
JS_DECLARE_NATIVE_FUNCTION(symbol_species_getter);
JS_DECLARE_NATIVE_FUNCTION(with_resolvers);
};
}

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@ -0,0 +1,56 @@
describe("errors", () => {
test("this value must be a constructor", () => {
expect(() => {
Promise.withResolvers.call(Symbol.hasInstance);
}).toThrowWithMessage(TypeError, "Symbol(Symbol.hasInstance) is not a constructor");
});
});
describe("normal behavior", () => {
test("length is 0", () => {
expect(Promise.withResolvers).toHaveLength(0);
});
test("returned promise is a Promise", () => {
const { promise, resolve, reject } = Promise.withResolvers();
expect(promise).toBeInstanceOf(Promise);
});
test("returned resolve/reject are unary functions", () => {
const { promise, resolve, reject } = Promise.withResolvers();
expect(resolve).toBeInstanceOf(Function);
expect(resolve).toHaveLength(1);
expect(reject).toBeInstanceOf(Function);
expect(reject).toHaveLength(1);
});
test("returned promise can be resolved", () => {
const { promise, resolve, reject } = Promise.withResolvers();
let fulfillmentValue = null;
promise.then(value => {
fulfillmentValue = value;
});
resolve("Some value");
runQueuedPromiseJobs();
expect(fulfillmentValue).toBe("Some value");
});
test("returned promise can be rejected", () => {
const { promise, resolve, reject } = Promise.withResolvers();
let rejectionReason = null;
promise.catch(value => {
rejectionReason = value;
});
reject("Some value");
runQueuedPromiseJobs();
expect(rejectionReason).toBe("Some value");
});
});