process: make tick callback and promise rejection callback more robust

- Rename `internalTickCallback` to `processTicksAndRejections`, make
  sure it does not get called if it's not set in C++.
- Rename `emitPromiseRejectionWarnings` to `processPromiseRejections`
  since it also emit events that are not warnings.
- Sets `SetPromiseRejectCallback` in the `Environment` constructor
  to make sure it only gets called once per-isolate, and make
  sure it does not get called if it's not set in C++.
- Wrap promise rejection callback initialization into
  `listenForRejections()`.
- Add comments.

PR-URL: nodejs#25200
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/process/next_tick.js

@@ -6,15 +6,14 @@ const {
   tickInfo,
   // Used to run V8's micro task queue.
   runMicrotasks,
-  setTickCallback,
-  initializePromiseRejectCallback
+  setTickCallback
 } = internalBinding('task_queue');
 
 const {
   setHasRejectionToWarn,
   hasRejectionToWarn,
-  promiseRejectHandler,
-  emitPromiseRejectionWarnings
+  listenForRejections,
+  processPromiseRejections
 } = require('internal/process/promises');
 
 const {
@@ -49,10 +48,10 @@ function runNextTicks() {
   if (!hasTickScheduled() && !hasRejectionToWarn())
     return;
 
-  internalTickCallback();
+  processTicksAndRejections();
 }
 
-function internalTickCallback() {
+function processTicksAndRejections() {
   let tock;
   do {
     while (tock = queue.shift()) {
@@ -80,7 +79,7 @@ function internalTickCallback() {
     }
     setHasTickScheduled(false);
     runMicrotasks();
-  } while (!queue.isEmpty() || emitPromiseRejectionWarnings());
+  } while (!queue.isEmpty() || processPromiseRejections());
   setHasRejectionToWarn(false);
 }
 
@@ -134,11 +133,10 @@ function nextTick(callback) {
 // 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

@@ -8,7 +8,8 @@ const {
     kPromiseHandlerAddedAfterReject,
     kPromiseResolveAfterResolved,
     kPromiseRejectAfterResolved
-  }
+  },
+  setPromiseRejectCallback
 } = internalBinding('task_queue');
 
 // *Must* match Environment::TickInfo::Fields in src/env.h.
@@ -117,7 +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)) {
@@ -142,9 +145,13 @@ function emitPromiseRejectionWarnings() {
   return maybeScheduledTicks || pendingUnhandledRejections.length !== 0;
 }
 
+function listenForRejections() {
+  setPromiseRejectCallback(promiseRejectHandler);
+}
+
 module.exports = {
   hasRejectionToWarn,
   setHasRejectionToWarn,
-  promiseRejectHandler,
-  emitPromiseRejectionWarnings
+  listenForRejections,
+  processPromiseRejections
 };

src/callback_scope.cc

@@ -5,6 +5,7 @@
 
 namespace node {
 
+using v8::Function;
 using v8::HandleScope;
 using v8::Isolate;
 using v8::Local;
@@ -114,8 +115,13 @@ void InternalCallbackScope::Close() {
 
   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.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/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

@@ -36,7 +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};
 
@@ -49,6 +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);
 
@@ -83,17 +87,12 @@ static void PromiseRejectCallback(PromiseRejectMessage message) {
       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>());
 }
 
@@ -120,8 +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

@@ -14,7 +14,7 @@ Error
     at startExecution (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:*:*)

test/message/stdin_messages.out

@@ -12,7 +12,7 @@ SyntaxError: Strict mode code may not include a with statement
     at Socket.process.stdin.on (internal/bootstrap/node.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process.internalTickCallback (internal/process/next_tick.js:*:*)
+    at processTicksAndRejections (internal/process/next_tick.js:*:*)
 42
 42
 [stdin]:1
@@ -29,7 +29,7 @@ Error: hello
     at Socket.process.stdin.on (internal/bootstrap/node.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process.internalTickCallback (internal/process/next_tick.js:*:*)
+    at processTicksAndRejections (internal/process/next_tick.js:*:*)
 [stdin]:1
 throw new Error("hello")
 ^
@@ -44,7 +44,7 @@ Error: hello
     at Socket.process.stdin.on (internal/bootstrap/node.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process.internalTickCallback (internal/process/next_tick.js:*:*)
+    at processTicksAndRejections (internal/process/next_tick.js:*:*)
 100
 [stdin]:1
 var x = 100; y = x;
@@ -60,7 +60,7 @@ ReferenceError: y is not defined
     at Socket.process.stdin.on (internal/bootstrap/node.js:*:*)
     at Socket.emit (events.js:*:*)
     at endReadableNT (_stream_readable.js:*:*)
-    at process.internalTickCallback (internal/process/next_tick.js:*:*)
+    at processTicksAndRejections (internal/process/next_tick.js:*:*)
 
 [stdin]:1
 var ______________________________________________; throw 10