process: refactor promise rejection handling

lib/internal/process/next_tick.js

@@ -6,13 +6,14 @@ const {
   tickInfo,
   // Used to run V8's micro task queue.
   runMicrotasks,
-  setTickCallback,
-  initializePromiseRejectCallback
+  setTickCallback
 } = internalBinding('task_queue');
 
 const {
-  promiseRejectHandler,
-  emitPromiseRejectionWarnings
+  setHasRejectionToWarn,
+  hasRejectionToWarn,
+  listenForRejections,
+  processPromiseRejections
 } = require('internal/process/promises');
 
 const {
@@ -30,21 +31,27 @@ const { ERR_INVALID_CALLBACK } = require('internal/errors').codes;
 const FixedQueue = require('internal/fixed_queue');
 
 // *Must* match Environment::TickInfo::Fields in src/env.h.
-const kHasScheduled = 0;
-const kHasPromiseRejections = 1;
+const kHasTickScheduled = 0;
+
+function hasTickScheduled() {
+  return tickInfo[kHasTickScheduled] === 1;
+}
+function setHasTickScheduled(value) {
+  tickInfo[kHasTickScheduled] = value ? 1 : 0;
+}
 
 const queue = new FixedQueue();
 
 function runNextTicks() {
-  if (tickInfo[kHasScheduled] === 0 && tickInfo[kHasPromiseRejections] === 0)
+  if (!hasTickScheduled() && !hasRejectionToWarn())
     runMicrotasks();
-  if (tickInfo[kHasScheduled] === 0 && tickInfo[kHasPromiseRejections] === 0)
+  if (!hasTickScheduled() && !hasRejectionToWarn())
     return;
 
-  internalTickCallback();
+  processTicksAndRejections();
 }
 
-function internalTickCallback() {
+function processTicksAndRejections() {
   let tock;
   do {
     while (tock = queue.shift()) {
@@ -70,10 +77,10 @@ function internalTickCallback() {
 
       emitAfter(asyncId);
     }
-    tickInfo[kHasScheduled] = 0;
+    setHasTickScheduled(false);
     runMicrotasks();
-  } while (!queue.isEmpty() || emitPromiseRejectionWarnings());
-  tickInfo[kHasPromiseRejections] = 0;
+  } while (!queue.isEmpty() || processPromiseRejections());
+  setHasRejectionToWarn(false);
 }
 
 class TickObject {
@@ -119,18 +126,17 @@ function nextTick(callback) {
   }
 
   if (queue.isEmpty())
-    tickInfo[kHasScheduled] = 1;
+    setHasTickScheduled(true);
   queue.push(new TickObject(callback, args, getDefaultTriggerAsyncId()));
 }
 
 // TODO(joyeecheung): make this a factory class so that node.js can
 // control the side effects caused by the initializers.
 exports.setup = function() {
-  // Initializes the per-isolate promise rejection callback which
-  // will call the handler being passed into this function.
-  initializePromiseRejectCallback(promiseRejectHandler);
+  // Sets the per-isolate promise rejection callback
+  listenForRejections();
   // Sets the callback to be run in every tick.
-  setTickCallback(internalTickCallback);
+  setTickCallback(processTicksAndRejections);
   return {
     nextTick,
     runNextTicks

lib/internal/process/promises.js

@@ -2,24 +2,46 @@
 
 const { safeToString } = internalBinding('util');
 const {
-  promiseRejectEvents
+  tickInfo,
+  promiseRejectEvents: {
+    kPromiseRejectWithNoHandler,
+    kPromiseHandlerAddedAfterReject,
+    kPromiseResolveAfterResolved,
+    kPromiseRejectAfterResolved
+  },
+  setPromiseRejectCallback
 } = internalBinding('task_queue');
 
+// *Must* match Environment::TickInfo::Fields in src/env.h.
+const kHasRejectionToWarn = 1;
+
 const maybeUnhandledPromises = new WeakMap();
 const pendingUnhandledRejections = [];
 const asyncHandledRejections = [];
 let lastPromiseId = 0;
 
+function setHasRejectionToWarn(value) {
+  tickInfo[kHasRejectionToWarn] = value ? 1 : 0;
+}
+
+function hasRejectionToWarn() {
+  return tickInfo[kHasRejectionToWarn] === 1;
+}
+
 function promiseRejectHandler(type, promise, reason) {
   switch (type) {
-    case promiseRejectEvents.kPromiseRejectWithNoHandler:
-      return unhandledRejection(promise, reason);
-    case promiseRejectEvents.kPromiseHandlerAddedAfterReject:
-      return handledRejection(promise);
-    case promiseRejectEvents.kPromiseResolveAfterResolved:
-      return resolveError('resolve', promise, reason);
-    case promiseRejectEvents.kPromiseRejectAfterResolved:
-      return resolveError('reject', promise, reason);
+    case kPromiseRejectWithNoHandler:
+      unhandledRejection(promise, reason);
+      break;
+    case kPromiseHandlerAddedAfterReject:
+      handledRejection(promise);
+      break;
+    case kPromiseResolveAfterResolved:
+      resolveError('resolve', promise, reason);
+      break;
+    case kPromiseRejectAfterResolved:
+      resolveError('reject', promise, reason);
+      break;
   }
 }
 
@@ -38,7 +60,7 @@ function unhandledRejection(promise, reason) {
     warned: false
   });
   pendingUnhandledRejections.push(promise);
-  return true;
+  setHasRejectionToWarn(true);
 }
 
 function handledRejection(promise) {
@@ -54,10 +76,11 @@ function handledRejection(promise) {
       warning.name = 'PromiseRejectionHandledWarning';
       warning.id = uid;
       asyncHandledRejections.push({ promise, warning });
-      return true;
+      setHasRejectionToWarn(true);
+      return;
     }
   }
-  return false;
+  setHasRejectionToWarn(false);
 }
 
 const unhandledRejectionErrName = 'UnhandledPromiseRejectionWarning';
@@ -95,7 +118,9 @@ function emitDeprecationWarning() {
   }
 }
 
-function emitPromiseRejectionWarnings() {
+// If this method returns true, at least one more tick need to be
+// scheduled to process any potential pending rejections
+function processPromiseRejections() {
   while (asyncHandledRejections.length > 0) {
     const { promise, warning } = asyncHandledRejections.shift();
     if (!process.emit('rejectionHandled', promise)) {
@@ -120,7 +145,13 @@ function emitPromiseRejectionWarnings() {
   return maybeScheduledTicks || pendingUnhandledRejections.length !== 0;
 }
 
+function listenForRejections() {
+  setPromiseRejectCallback(promiseRejectHandler);
+}
+
 module.exports = {
-  promiseRejectHandler,
-  emitPromiseRejectionWarnings
+  hasRejectionToWarn,
+  setHasRejectionToWarn,
+  listenForRejections,
+  processPromiseRejections
 };

src/callback_scope.cc

@@ -5,6 +5,7 @@
 
 namespace node {
 
+using v8::Function;
 using v8::HandleScope;
 using v8::Isolate;
 using v8::Local;
@@ -95,7 +96,7 @@ void InternalCallbackScope::Close() {
   Environment::TickInfo* tick_info = env_->tick_info();
 
   if (!env_->can_call_into_js()) return;
-  if (!tick_info->has_scheduled()) {
+  if (!tick_info->has_tick_scheduled()) {
     env_->isolate()->RunMicrotasks();
   }
 
@@ -106,16 +107,21 @@ void InternalCallbackScope::Close() {
     CHECK_EQ(env_->trigger_async_id(), 0);
   }
 
-  if (!tick_info->has_scheduled() && !tick_info->has_promise_rejections()) {
+  if (!tick_info->has_tick_scheduled() && !tick_info->has_rejection_to_warn()) {
     return;
   }
 
   Local<Object> process = env_->process_object();
 
   if (!env_->can_call_into_js()) return;
 
-  if (env_->tick_callback_function()
-      ->Call(env_->context(), process, 0, nullptr).IsEmpty()) {
+  Local<Function> tick_callback = env_->tick_callback_function();
+
+  // The tick is triggered before JS land calls SetTickCallback
+  // to initializes the tick callback during bootstrap.
+  CHECK(!tick_callback.IsEmpty());
+
+  if (tick_callback->Call(env_->context(), process, 0, nullptr).IsEmpty()) {
     failed_ = true;
   }
 }

src/env-inl.h

@@ -265,16 +265,12 @@ inline AliasedBuffer<uint8_t, v8::Uint8Array>& Environment::TickInfo::fields() {
   return fields_;
 }
 
-inline bool Environment::TickInfo::has_scheduled() const {
-  return fields_[kHasScheduled] == 1;
+inline bool Environment::TickInfo::has_tick_scheduled() const {
+  return fields_[kHasTickScheduled] == 1;
 }
 
-inline bool Environment::TickInfo::has_promise_rejections() const {
-  return fields_[kHasPromiseRejections] == 1;
-}
-
-inline void Environment::TickInfo::promise_rejections_toggle_on() {
-  fields_[kHasPromiseRejections] = 1;
+inline bool Environment::TickInfo::has_rejection_to_warn() const {
+  return fields_[kHasRejectionToWarn] == 1;
 }
 
 inline void Environment::AssignToContext(v8::Local<v8::Context> context,

src/env.cc

@@ -241,6 +241,10 @@ Environment::Environment(IsolateData* isolate_data,
   if (options_->no_force_async_hooks_checks) {
     async_hooks_.no_force_checks();
   }
+
+  // TODO(addaleax): the per-isolate state should not be controlled by
+  // a single Environment.
+  isolate()->SetPromiseRejectCallback(task_queue::PromiseRejectCallback);
 }
 
 Environment::~Environment() {

src/env.h

@@ -574,18 +574,16 @@ class Environment {
   class TickInfo {
    public:
     inline AliasedBuffer<uint8_t, v8::Uint8Array>& fields();
-    inline bool has_scheduled() const;
-    inline bool has_promise_rejections() const;
-
-    inline void promise_rejections_toggle_on();
+    inline bool has_tick_scheduled() const;
+    inline bool has_rejection_to_warn() const;
 
    private:
     friend class Environment;  // So we can call the constructor.
     inline explicit TickInfo(v8::Isolate* isolate);
 
     enum Fields {
-      kHasScheduled,
-      kHasPromiseRejections,
+      kHasTickScheduled = 0,
+      kHasRejectionToWarn,
       kFieldsCount
     };
 

src/node_internals.h

@@ -180,6 +180,10 @@ SlicedArguments::SlicedArguments(
   size_ = size;
 }
 
+namespace task_queue {
+void PromiseRejectCallback(v8::PromiseRejectMessage message);
+}  // namespace task_queue
+
 v8::Maybe<bool> ProcessEmitWarning(Environment* env, const char* fmt, ...);
 v8::Maybe<bool> ProcessEmitDeprecationWarning(Environment* env,
                                               const char* warning,

src/node_task_queue.cc

@@ -17,7 +17,6 @@ using v8::kPromiseRejectAfterResolved;
 using v8::kPromiseRejectWithNoHandler;
 using v8::kPromiseResolveAfterResolved;
 using v8::Local;
-using v8::MaybeLocal;
 using v8::Number;
 using v8::Object;
 using v8::Promise;
@@ -37,7 +36,7 @@ static void SetTickCallback(const FunctionCallbackInfo<Value>& args) {
   env->set_tick_callback_function(args[0].As<Function>());
 }
 
-static void PromiseRejectCallback(PromiseRejectMessage message) {
+void PromiseRejectCallback(PromiseRejectMessage message) {
   static std::atomic<uint64_t> unhandledRejections{0};
   static std::atomic<uint64_t> rejectionsHandledAfter{0};
 
@@ -50,6 +49,10 @@ static void PromiseRejectCallback(PromiseRejectMessage message) {
   if (env == nullptr) return;
 
   Local<Function> callback = env->promise_reject_callback();
+  // The promise is rejected before JS land calls SetPromiseRejectCallback
+  // to initializes the promise reject callback during bootstrap.
+  CHECK(!callback.IsEmpty());
+
   Local<Value> value;
   Local<Value> type = Number::New(env->isolate(), event);
 
@@ -80,26 +83,16 @@ static void PromiseRejectCallback(PromiseRejectMessage message) {
   }
 
   Local<Value> args[] = { type, promise, value };
-  MaybeLocal<Value> ret = callback->Call(env->context(),
-                                         Undefined(isolate),
-                                         arraysize(args),
-                                         args);
-
-  if (!ret.IsEmpty() && ret.ToLocalChecked()->IsTrue())
-    env->tick_info()->promise_rejections_toggle_on();
+  USE(callback->Call(
+      env->context(), Undefined(isolate), arraysize(args), args));
 }
 
-static void InitializePromiseRejectCallback(
+static void SetPromiseRejectCallback(
     const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   Isolate* isolate = env->isolate();
 
   CHECK(args[0]->IsFunction());
-
-  // TODO(joyeecheung): this may be moved to somewhere earlier in the bootstrap
-  // to make sure it's only called once
-  isolate->SetPromiseRejectCallback(PromiseRejectCallback);
-
   env->set_promise_reject_callback(args[0].As<Function>());
 }
 
@@ -126,8 +119,8 @@ static void Initialize(Local<Object> target,
               FIXED_ONE_BYTE_STRING(isolate, "promiseRejectEvents"),
               events).FromJust();
   env->SetMethod(target,
-                 "initializePromiseRejectCallback",
-                 InitializePromiseRejectCallback);
+                 "setPromiseRejectCallback",
+                 SetPromiseRejectCallback);
 }
 
 }  // namespace task_queue

test/message/events_unhandled_error_nexttick.out

@@ -15,7 +15,7 @@ Error
     at startup (internal/bootstrap/node.js:*:*)
 Emitted 'error' event at:
     at process.nextTick (*events_unhandled_error_nexttick.js:*:*)
-    at internalTickCallback (internal/process/next_tick.js:*:*)
+    at processTicksAndRejections (internal/process/next_tick.js:*:*)
     at process.runNextTicks [as _tickCallback] (internal/process/next_tick.js:*:*)
     at Function.Module.runMain (internal/modules/cjs/loader.js:*:*)
     at executeUserCode (internal/bootstrap/node.js:*:*)

test/message/nexttick_throw.out

@@ -4,7 +4,7 @@
         ^
 ReferenceError: undefined_reference_error_maker is not defined
     at *test*message*nexttick_throw.js:*:*
-    at internalTickCallback (internal/process/next_tick.js:*:*)
+    at processTicksAndRejections (internal/process/next_tick.js:*:*)
     at process.runNextTicks [as _tickCallback] (internal/process/next_tick.js:*:*)
     at Function.Module.runMain (internal/modules/cjs/loader.js:*:*)
     at executeUserCode (internal/bootstrap/node.js:*:*)