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/*
* Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
* Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/TypeCasts.h>
#include <LibCore/EventLoop.h>
#include <LibJS/Runtime/Completion.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/PromiseConstructor.h>
#include <LibJS/Runtime/PromiseReaction.h>
#include <LibJS/Runtime/VM.h>
#include <LibJS/Runtime/Value.h>
namespace JS {
Completion::Completion(ThrowCompletionOr<Value> const& throw_completion_or_value)
{
if (throw_completion_or_value.is_throw_completion()) {
m_type = Type::Throw;
m_value = throw_completion_or_value.throw_completion().value();
} else {
m_type = Type::Normal;
m_value = throw_completion_or_value.value();
}
}
// 6.2.3.1 Await, https://tc39.es/ecma262/#await
ThrowCompletionOr<Value> await(VM& vm, Value value)
{
auto& realm = *vm.current_realm();
// 1. Let asyncContext be the running execution context.
// NOTE: This is not needed, as we don't suspend anything.
// 2. Let promise be ? PromiseResolve(%Promise%, value).
auto* promise_object = TRY(promise_resolve(vm, *realm.intrinsics().promise_constructor(), value));
Optional<bool> success;
Value result;
// 3. Let fulfilledClosure be a new Abstract Closure with parameters (value) that captures asyncContext and performs the following steps when called:
auto fulfilled_closure = [&success, &result](VM& vm) -> ThrowCompletionOr<Value> {
// a. Let prevContext be the running execution context.
// b. Suspend prevContext.
// FIXME: We don't have this concept yet.
// NOTE: Since we don't support context suspension, we exfiltrate the result to await()'s scope instead
success = true;
result = vm.argument(0);
// c. Push asyncContext onto the execution context stack; asyncContext is now the running execution context.
// NOTE: This is not done, because we're not suspending anything (see above).
// d. Resume the suspended evaluation of asyncContext using NormalCompletion(value) as the result of the operation that suspended it.
// e. Assert: When we reach this step, asyncContext has already been removed from the execution context stack and prevContext is the currently running execution context.
// FIXME: We don't have this concept yet.
// f. Return undefined.
return js_undefined();
};
// 4. Let onFulfilled be CreateBuiltinFunction(fulfilledClosure, 1, "", « »).
auto* on_fulfilled = NativeFunction::create(realm, move(fulfilled_closure), 1, "");
// 5. Let rejectedClosure be a new Abstract Closure with parameters (reason) that captures asyncContext and performs the following steps when called:
auto rejected_closure = [&success, &result](VM& vm) -> ThrowCompletionOr<Value> {
// a. Let prevContext be the running execution context.
// b. Suspend prevContext.
// FIXME: We don't have this concept yet.
// NOTE: Since we don't support context suspension, we exfiltrate the result to await()'s scope instead
success = false;
result = vm.argument(0);
// c. Push asyncContext onto the execution context stack; asyncContext is now the running execution context.
// NOTE: This is not done, because we're not suspending anything (see above).
// d. Resume the suspended evaluation of asyncContext using ThrowCompletion(reason) as the result of the operation that suspended it.
// e. Assert: When we reach this step, asyncContext has already been removed from the execution context stack and prevContext is the currently running execution context.
// FIXME: We don't have this concept yet.
// f. Return undefined.
return js_undefined();
};
// 6. Let onRejected be CreateBuiltinFunction(rejectedClosure, 1, "", « »).
auto* on_rejected = NativeFunction::create(realm, move(rejected_closure), 1, "");
// 7. Perform PerformPromiseThen(promise, onFulfilled, onRejected).
auto* promise = verify_cast<Promise>(promise_object);
promise->perform_then(on_fulfilled, on_rejected, {});
// FIXME: Since we don't support context suspension, we attempt to "wait" for the promise to resolve
// by letting the event loop spin until our promise is no longer pending, and then synchronously
// running all queued promise jobs.
// Note: This is not used by LibJS itself, and is performed for the embedder (i.e. LibWeb).
if (auto* custom_data = vm.custom_data()) {
custom_data->spin_event_loop_until([&] {
return success.has_value();
});
}
// 8. Remove asyncContext from the execution context stack and restore the execution context that is at the top of the execution context stack as the running execution context.
// NOTE: Since we don't push any EC, this step is not performed.
// 9. Set the code evaluation state of asyncContext such that when evaluation is resumed with a Completion Record completion, the following steps of the algorithm that invoked Await will be performed, with completion available.
// 10. Return NormalCompletion(unused).
// 11. NOTE: This returns to the evaluation of the operation that had most previously resumed evaluation of asyncContext.
vm.run_queued_promise_jobs();
// Make sure that the promise _actually_ resolved.
// Note that this is checked down the chain (result.is_empty()) anyway, but let's make the source of the issue more clear.
VERIFY(success.has_value());
if (success.value())
return result;
return throw_completion(result);
}
}
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