gecko-dev/dom/promise/PromiseDebugging.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "js/Value.h"
#include "nsThreadUtils.h"

#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/RefPtr.h"
#include "mozilla/SystemGroup.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/TimeStamp.h"

#include "mozilla/dom/BindingDeclarations.h"
#include "mozilla/dom/ContentChild.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/PromiseBinding.h"
#include "mozilla/dom/PromiseDebugging.h"
#include "mozilla/dom/PromiseDebuggingBinding.h"

namespace mozilla {
namespace dom {

class FlushRejections: public CancelableRunnable
{
public:
  FlushRejections() : CancelableRunnable("dom::FlushRejections") {}

  static void Init() {
    if (!sDispatched.init()) {
      MOZ_CRASH("Could not initialize FlushRejections::sDispatched");
    }
    sDispatched.set(false);
  }

  static void DispatchNeeded() {
    if (sDispatched.get()) {
      // An instance of `FlushRejections` has already been dispatched
      // and not run yet. No need to dispatch another one.
      return;
    }
    sDispatched.set(true);
    SystemGroup::Dispatch(TaskCategory::Other,
                          do_AddRef(new FlushRejections()));
  }

  static void FlushSync() {
    sDispatched.set(false);

    // Call the callbacks if necessary.
    // Note that these callbacks may in turn cause Promise to turn
    // uncaught or consumed. Since `sDispatched` is `false`,
    // `FlushRejections` will be called once again, on an ulterior
    // tick.
    PromiseDebugging::FlushUncaughtRejectionsInternal();
  }

  NS_IMETHOD Run() override {
    FlushSync();
    return NS_OK;
  }

private:
  // `true` if an instance of `FlushRejections` is currently dispatched
  // and has not been executed yet.
  static MOZ_THREAD_LOCAL(bool) sDispatched;
};

/* static */ MOZ_THREAD_LOCAL(bool)
FlushRejections::sDispatched;

/* static */ void
PromiseDebugging::GetState(GlobalObject& aGlobal, JS::Handle<JSObject*> aPromise,
                           PromiseDebuggingStateHolder& aState,
                           ErrorResult& aRv)
{
  JSContext* cx = aGlobal.Context();
  JS::Rooted<JSObject*> obj(cx, js::CheckedUnwrap(aPromise));
  if (!obj || !JS::IsPromiseObject(obj)) {
    aRv.ThrowTypeError<MSG_IS_NOT_PROMISE>(NS_LITERAL_STRING(
        "Argument of PromiseDebugging.getState"));
    return;
  }
  switch (JS::GetPromiseState(obj)) {
  case JS::PromiseState::Pending:
    aState.mState = PromiseDebuggingState::Pending;
    break;
  case JS::PromiseState::Fulfilled:
    aState.mState = PromiseDebuggingState::Fulfilled;
    aState.mValue = JS::GetPromiseResult(obj);
    break;
  case JS::PromiseState::Rejected:
    aState.mState = PromiseDebuggingState::Rejected;
    aState.mReason = JS::GetPromiseResult(obj);
    break;
  }
}

/* static */ void
PromiseDebugging::GetPromiseID(GlobalObject& aGlobal,
                               JS::Handle<JSObject*> aPromise,
                               nsString& aID,
                               ErrorResult& aRv)
{
  JSContext* cx = aGlobal.Context();
  JS::Rooted<JSObject*> obj(cx, js::CheckedUnwrap(aPromise));
  if (!obj || !JS::IsPromiseObject(obj)) {
    aRv.ThrowTypeError<MSG_IS_NOT_PROMISE>(NS_LITERAL_STRING(
        "Argument of PromiseDebugging.getState"));
    return;
  }
  uint64_t promiseID = JS::GetPromiseID(obj);
  aID = sIDPrefix;
  aID.AppendInt(promiseID);
}

/* static */ void
PromiseDebugging::GetAllocationStack(GlobalObject& aGlobal,
                                     JS::Handle<JSObject*> aPromise,
                                     JS::MutableHandle<JSObject*> aStack,
                                     ErrorResult& aRv)
{
  JSContext* cx = aGlobal.Context();
  JS::Rooted<JSObject*> obj(cx, js::CheckedUnwrap(aPromise));
  if (!obj || !JS::IsPromiseObject(obj)) {
    aRv.ThrowTypeError<MSG_IS_NOT_PROMISE>(NS_LITERAL_STRING(
        "Argument of PromiseDebugging.getAllocationStack"));
    return;
  }
  aStack.set(JS::GetPromiseAllocationSite(obj));
}

/* static */ void
PromiseDebugging::GetRejectionStack(GlobalObject& aGlobal,
                                    JS::Handle<JSObject*> aPromise,
                                    JS::MutableHandle<JSObject*> aStack,
                                    ErrorResult& aRv)
{
  JSContext* cx = aGlobal.Context();
  JS::Rooted<JSObject*> obj(cx, js::CheckedUnwrap(aPromise));
  if (!obj || !JS::IsPromiseObject(obj)) {
    aRv.ThrowTypeError<MSG_IS_NOT_PROMISE>(NS_LITERAL_STRING(
        "Argument of PromiseDebugging.getRejectionStack"));
    return;
  }
  aStack.set(JS::GetPromiseResolutionSite(obj));
}

/* static */ void
PromiseDebugging::GetFullfillmentStack(GlobalObject& aGlobal,
                                       JS::Handle<JSObject*> aPromise,
                                       JS::MutableHandle<JSObject*> aStack,
                                       ErrorResult& aRv)
{
  JSContext* cx = aGlobal.Context();
  JS::Rooted<JSObject*> obj(cx, js::CheckedUnwrap(aPromise));
  if (!obj || !JS::IsPromiseObject(obj)) {
    aRv.ThrowTypeError<MSG_IS_NOT_PROMISE>(NS_LITERAL_STRING(
        "Argument of PromiseDebugging.getFulfillmentStack"));
    return;
  }
  aStack.set(JS::GetPromiseResolutionSite(obj));
}

/*static */ nsString
PromiseDebugging::sIDPrefix;

/* static */ void
PromiseDebugging::Init()
{
  FlushRejections::Init();

  // Generate a prefix for identifiers: "PromiseDebugging.$processid."
  sIDPrefix = NS_LITERAL_STRING("PromiseDebugging.");
  if (XRE_IsContentProcess()) {
    sIDPrefix.AppendInt(ContentChild::GetSingleton()->GetID());
    sIDPrefix.Append('.');
  } else {
    sIDPrefix.AppendLiteral("0.");
  }
}

/* static */ void
PromiseDebugging::Shutdown()
{
  sIDPrefix.SetIsVoid(true);
}

/* static */ void
PromiseDebugging::FlushUncaughtRejections()
{
  MOZ_ASSERT(!NS_IsMainThread());
  FlushRejections::FlushSync();
}

/* static */ void
PromiseDebugging::AddUncaughtRejectionObserver(GlobalObject&,
                                               UncaughtRejectionObserver& aObserver)
{
  CycleCollectedJSContext* storage = CycleCollectedJSContext::Get();
  nsTArray<nsCOMPtr<nsISupports>>& observers = storage->mUncaughtRejectionObservers;
  observers.AppendElement(&aObserver);
}

/* static */ bool
PromiseDebugging::RemoveUncaughtRejectionObserver(GlobalObject&,
                                                  UncaughtRejectionObserver& aObserver)
{
  CycleCollectedJSContext* storage = CycleCollectedJSContext::Get();
  nsTArray<nsCOMPtr<nsISupports>>& observers = storage->mUncaughtRejectionObservers;
  for (size_t i = 0; i < observers.Length(); ++i) {
    UncaughtRejectionObserver* observer = static_cast<UncaughtRejectionObserver*>(observers[i].get());
    if (*observer == aObserver) {
      observers.RemoveElementAt(i);
      return true;
    }
  }
  return false;
}

/* static */ void
PromiseDebugging::AddUncaughtRejection(JS::HandleObject aPromise)
{
  // This might OOM, but won't set a pending exception, so we'll just ignore it.
  if (CycleCollectedJSContext::Get()->mUncaughtRejections.append(aPromise)) {
    FlushRejections::DispatchNeeded();
  }
}

/* void */ void
PromiseDebugging::AddConsumedRejection(JS::HandleObject aPromise)
{
  // If the promise is in our list of uncaught rejections, we haven't yet
  // reported it as unhandled. In that case, just remove it from the list
  // and don't add it to the list of consumed rejections.
  auto& uncaughtRejections = CycleCollectedJSContext::Get()->mUncaughtRejections;
  for (size_t i = 0; i < uncaughtRejections.length(); i++) {
    if (uncaughtRejections[i] == aPromise) {
      // To avoid large amounts of memmoves, we don't shrink the vector here.
      // Instead, we filter out nullptrs when iterating over the vector later.
      uncaughtRejections[i].set(nullptr);
      return;
    }
  }
  // This might OOM, but won't set a pending exception, so we'll just ignore it.
  if (CycleCollectedJSContext::Get()->mConsumedRejections.append(aPromise)) {
    FlushRejections::DispatchNeeded();
  }
}

/* static */ void
PromiseDebugging::FlushUncaughtRejectionsInternal()
{
  CycleCollectedJSContext* storage = CycleCollectedJSContext::Get();

  auto& uncaught = storage->mUncaughtRejections;
  auto& consumed = storage->mConsumedRejections;

  AutoJSAPI jsapi;
  jsapi.Init();
  JSContext* cx = jsapi.cx();

  // Notify observers of uncaught Promise.
  auto& observers = storage->mUncaughtRejectionObservers;

  for (size_t i = 0; i < uncaught.length(); i++) {
    JS::RootedObject promise(cx, uncaught[i]);
    // Filter out nullptrs which might've been added by
    // PromiseDebugging::AddConsumedRejection.
    if (!promise) {
      continue;
    }

    for (size_t j = 0; j < observers.Length(); ++j) {
      RefPtr<UncaughtRejectionObserver> obs =
        static_cast<UncaughtRejectionObserver*>(observers[j].get());

      obs->OnLeftUncaught(promise, IgnoreErrors());
    }
    JSAutoCompartment ac(cx, promise);
    Promise::ReportRejectedPromise(cx, promise);
  }
  storage->mUncaughtRejections.clear();

  // Notify observers of consumed Promise.

  for (size_t i = 0; i < consumed.length(); i++) {
    JS::RootedObject promise(cx, consumed[i]);

    for (size_t j = 0; j < observers.Length(); ++j) {
      RefPtr<UncaughtRejectionObserver> obs =
        static_cast<UncaughtRejectionObserver*>(observers[j].get());

      obs->OnConsumed(promise, IgnoreErrors());
    }
  }
  storage->mConsumedRejections.clear();
}

} // namespace dom
} // namespace mozilla