worker: add ports property to MessageEvents

Add `ev.ports` for spec compliancy.

Since we only emit the raw `data` value, and only create the
`MessageEvent` instance if there are EventTarget-style listeners,
we store the ports list temporarily on the MessagePort object itself,
so that we can look it up when we need to create the event object.

Fixes: #37358

PR-URL: #37538
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Joyee Cheung <[email protected]>

Author: addaleax

lib/internal/per_context/messageport.js

@@ -4,22 +4,30 @@ const {
 } = primordials;
 
 class MessageEvent {
-  constructor(data, target, type) {
+  constructor(data, target, type, ports) {
     this.data = data;
     this.target = target;
     this.type = type;
+    this.ports = ports ?? [];
   }
 }
 
 const kHybridDispatch = SymbolFor('nodejs.internal.kHybridDispatch');
+const kCurrentlyReceivingPorts =
+  SymbolFor('nodejs.internal.kCurrentlyReceivingPorts');
 
-exports.emitMessage = function(data, type) {
+exports.emitMessage = function(data, ports, type) {
   if (typeof this[kHybridDispatch] === 'function') {
-    this[kHybridDispatch](data, type, undefined);
+    this[kCurrentlyReceivingPorts] = ports;
+    try {
+      this[kHybridDispatch](data, type, undefined);
+    } finally {
+      this[kCurrentlyReceivingPorts] = undefined;
+    }
     return;
   }
 
-  const event = new MessageEvent(data, this, type);
+  const event = new MessageEvent(data, this, type, ports);
   if (type === 'message') {
     if (typeof this.onmessage === 'function')
       this.onmessage(event);

lib/internal/worker/io.js

@@ -15,6 +15,7 @@ const {
   ObjectSetPrototypeOf,
   ReflectApply,
   Symbol,
+  SymbolFor,
 } = primordials;
 
 const {
@@ -70,6 +71,8 @@ const kWritableCallbacks = Symbol('kWritableCallbacks');
 const kSource = Symbol('kSource');
 const kStartedReading = Symbol('kStartedReading');
 const kStdioWantsMoreDataCallback = Symbol('kStdioWantsMoreDataCallback');
+const kCurrentlyReceivingPorts =
+  SymbolFor('nodejs.internal.kCurrentlyReceivingPorts');
 
 const messageTypes = {
   UP_AND_RUNNING: 'upAndRunning',
@@ -150,7 +153,9 @@ ObjectDefineProperty(
       if (type !== 'message' && type !== 'messageerror') {
         return ReflectApply(originalCreateEvent, this, arguments);
       }
-      return new MessageEvent(type, { data });
+      const ports = this[kCurrentlyReceivingPorts];
+      this[kCurrentlyReceivingPorts] = undefined;
+      return new MessageEvent(type, { data, ports });
     },
     configurable: false,
     writable: false,
@@ -161,6 +166,7 @@ ObjectDefineProperty(
 function oninit() {
   initNodeEventTarget(this);
   setupPortReferencing(this, this, 'message');
+  this[kCurrentlyReceivingPorts] = undefined;
 }
 
 defineEventHandler(MessagePort.prototype, 'message');

src/node_messaging.cc

@@ -126,11 +126,18 @@ class DeserializerDelegate : public ValueDeserializer::Delegate {
 }  // anonymous namespace
 
 MaybeLocal<Value> Message::Deserialize(Environment* env,
-                                       Local<Context> context) {
+                                       Local<Context> context,
+                                       Local<Value>* port_list) {
+  Context::Scope context_scope(context);
+
   CHECK(!IsCloseMessage());
+  if (port_list != nullptr && !transferables_.empty()) {
+    // Need to create this outside of the EscapableHandleScope, but inside
+    // the Context::Scope.
+    *port_list = Array::New(env->isolate());
+  }
 
   EscapableHandleScope handle_scope(env->isolate());
-  Context::Scope context_scope(context);
 
   // Create all necessary objects for transferables, e.g. MessagePort handles.
   std::vector<BaseObjectPtr<BaseObject>> host_objects(transferables_.size());
@@ -146,10 +153,27 @@ MaybeLocal<Value> Message::Deserialize(Environment* env,
   });
 
   for (uint32_t i = 0; i < transferables_.size(); ++i) {
+    HandleScope handle_scope(env->isolate());
     TransferData* data = transferables_[i].get();
     host_objects[i] = data->Deserialize(
         env, context, std::move(transferables_[i]));
     if (!host_objects[i]) return {};
+    if (port_list != nullptr) {
+      // If we gather a list of all message ports, and this transferred object
+      // is a message port, add it to that list. This is a bit of an odd case
+      // of special handling for MessagePorts (as opposed to applying to all
+      // transferables), but it's required for spec compliancy.
+      DCHECK((*port_list)->IsArray());
+      Local<Array> port_list_array = port_list->As<Array>();
+      Local<Object> obj = host_objects[i]->object();
+      if (env->message_port_constructor_template()->HasInstance(obj)) {
+        if (port_list_array->Set(context,
+                                 port_list_array->Length(),
+                                 obj).IsNothing()) {
+          return {};
+        }
+      }
+    }
   }
   transferables_.clear();
 
@@ -664,7 +688,8 @@ MessagePort* MessagePort::New(
 }
 
 MaybeLocal<Value> MessagePort::ReceiveMessage(Local<Context> context,
-                                              MessageProcessingMode mode) {
+                                              MessageProcessingMode mode,
+                                              Local<Value>* port_list) {
   std::shared_ptr<Message> received;
   {
     // Get the head of the message queue.
@@ -696,7 +721,7 @@ MaybeLocal<Value> MessagePort::ReceiveMessage(Local<Context> context,
 
   if (!env()->can_call_into_js()) return MaybeLocal<Value>();
 
-  return received->Deserialize(env(), context);
+  return received->Deserialize(env(), context, port_list);
 }
 
 void MessagePort::OnMessage(MessageProcessingMode mode) {
@@ -735,14 +760,15 @@ void MessagePort::OnMessage(MessageProcessingMode mode) {
     Local<Function> emit_message = PersistentToLocal::Strong(emit_message_fn_);
 
     Local<Value> payload;
+    Local<Value> port_list = Undefined(env()->isolate());
     Local<Value> message_error;
-    Local<Value> argv[2];
+    Local<Value> argv[3];
 
     {
       // Catch any exceptions from parsing the message itself (not from
       // emitting it) as 'messageeror' events.
       TryCatchScope try_catch(env());
-      if (!ReceiveMessage(context, mode).ToLocal(&payload)) {
+      if (!ReceiveMessage(context, mode, &port_list).ToLocal(&payload)) {
         if (try_catch.HasCaught() && !try_catch.HasTerminated())
           message_error = try_catch.Exception();
         goto reschedule;
@@ -757,13 +783,15 @@ void MessagePort::OnMessage(MessageProcessingMode mode) {
     }
 
     argv[0] = payload;
-    argv[1] = env()->message_string();
+    argv[1] = port_list;
+    argv[2] = env()->message_string();
 
     if (MakeCallback(emit_message, arraysize(argv), argv).IsEmpty()) {
     reschedule:
       if (!message_error.IsEmpty()) {
         argv[0] = message_error;
-        argv[1] = env()->messageerror_string();
+        argv[1] = Undefined(env()->isolate());
+        argv[2] = env()->messageerror_string();
         USE(MakeCallback(emit_message, arraysize(argv), argv));
       }
 

src/node_messaging.h

@@ -62,8 +62,10 @@ class Message : public MemoryRetainer {
 
   // Deserialize the contained JS value. May only be called once, and only
   // after Serialize() has been called (e.g. by another thread).
-  v8::MaybeLocal<v8::Value> Deserialize(Environment* env,
-                                        v8::Local<v8::Context> context);
+  v8::MaybeLocal<v8::Value> Deserialize(
+      Environment* env,
+      v8::Local<v8::Context> context,
+      v8::Local<v8::Value>* port_list = nullptr);
 
   // Serialize a JS value, and optionally transfer objects, into this message.
   // The Message object retains ownership of all transferred objects until
@@ -293,8 +295,10 @@ class MessagePort : public HandleWrap {
   void OnClose() override;
   void OnMessage(MessageProcessingMode mode);
   void TriggerAsync();
-  v8::MaybeLocal<v8::Value> ReceiveMessage(v8::Local<v8::Context> context,
-                                           MessageProcessingMode mode);
+  v8::MaybeLocal<v8::Value> ReceiveMessage(
+      v8::Local<v8::Context> context,
+      MessageProcessingMode mode,
+      v8::Local<v8::Value>* port_list = nullptr);
 
   std::unique_ptr<MessagePortData> data_ = nullptr;
   bool receiving_messages_ = false;

test/parallel/test-worker-message-port-move.js

@@ -34,9 +34,13 @@ vm.runInContext('(' + function() {
 
     assert(!(port instanceof MessagePort));
     assert.strictEqual(port.onmessage, undefined);
-    port.onmessage = function({ data }) {
+    port.onmessage = function({ data, ports }) {
       assert(data instanceof Object);
-      port.postMessage(data);
+      assert(ports instanceof Array);
+      assert.strictEqual(ports.length, 1);
+      assert.strictEqual(ports[0], data.p);
+      assert(!(data.p instanceof MessagePort));
+      port.postMessage({});
     };
     port.start();
   }
@@ -55,8 +59,10 @@ vm.runInContext('(' + function() {
   }
 } + ')()', context);
 
+const otherChannel = new MessageChannel();
 port2.on('message', common.mustCall((msg) => {
   assert(msg instanceof Object);
   port2.close();
+  otherChannel.port2.close();
 }));
-port2.postMessage({});
+port2.postMessage({ p: otherChannel.port1 }, [ otherChannel.port1 ]);

test/parallel/test-worker-message-port.js

@@ -34,6 +34,7 @@ const { MessageChannel, MessagePort } = require('worker_threads');
   port1.onmessage = common.mustCall((message) => {
     assert.strictEqual(message.data, 4);
     assert.strictEqual(message.target, port1);
+    assert.deepStrictEqual(message.ports, []);
     port2.close(common.mustCall());
   });
 
@@ -161,6 +162,19 @@ const { MessageChannel, MessagePort } = require('worker_threads');
   port1.close();
 }
 
+{
+  // Test MessageEvent#ports
+  const c1 = new MessageChannel();
+  const c2 = new MessageChannel();
+  c1.port1.postMessage({ port: c2.port2 }, [ c2.port2 ]);
+  c1.port2.addEventListener('message', common.mustCall((ev) => {
+    assert.strictEqual(ev.ports.length, 1);
+    assert.strictEqual(ev.ports[0].constructor, MessagePort);
+    c1.port1.close();
+    c2.port1.close();
+  }));
+}
+
 {
   assert.deepStrictEqual(
     Object.getOwnPropertyNames(MessagePort.prototype).sort(),