MessagePort: implement NodeEventTarget on the native listener list

src/js/builtins.d.ts

@@ -475,6 +475,12 @@ declare interface AddEventListenerOptions {
    * internal `kResistStopPropagation`.
    */
   $kResistStopPropagation?: boolean;
+  /**
+   * Private symbol read by the native EventTarget. A listener registered with it is
+   * invoked with the event's underlying value (data / detail / error) instead of the
+   * Event wrapper. Mirrors Node.js's internal `kIsNodeStyleListener`.
+   */
+  $kIsNodeStyleListener?: boolean;
 }
 
 declare class OutOfMemoryError {

src/js/builtins/BunBuiltinNames.h

@@ -119,6 +119,7 @@ using namespace JSC;
     macro(isUntransferable) \
     macro(join) \
     macro(json) \
+    macro(kIsNodeStyleListener) \
     macro(kResistStopPropagation) \
     macro(key) \
     macro(lazy) \

src/js/node/worker_threads.ts

@@ -101,189 +101,7 @@ type NodeWorkerOptions = import("node:worker_threads").WorkerOptions;
 // after their Worker exits
 let urlRevokeRegistry: FinalizationRegistry<string> | undefined = undefined;
 
-function injectFakeEmitter(Class) {
-  // Per-instance registry mapping each event to (user listener -> wrapper), so
-  // listenerCount/eventNames/removeAllListeners work over EventTarget's opaque
-  // internal map and off() can find the wrapper a given listener registered.
-  // SafeMap: its prototype is a frozen, null-proto snapshot of Map.prototype, so
-  // .get/.set/.size/.values()/iteration all bypass a user-replaced Map.prototype.
-  // (It has no @get/@set private names, so the $-intrinsics don't apply to it.)
-  // Keyed by a module-local symbol, not a WeakMap — WeakMap has neither defence.
-  const kListenerRegistry = Symbol("listenerRegistry");
-  function registryFor(target, create) {
-    let map = target[kListenerRegistry];
-    if (!map && create) target[kListenerRegistry] = map = new SafeMap();
-    return map;
-  }
-
-  function messageEventHandler(event: MessageEvent) {
-    return event.data;
-  }
-
-  function errorEventHandler(event: ErrorEvent) {
-    return event.error;
-  }
-
-  function customEventHandler(event) {
-    return event.detail;
-  }
-
-  function wrapped(run, listener) {
-    return function (event) {
-      return listener(run(event));
-    };
-  }
-
-  function functionForEventType(event, listener) {
-    switch (event) {
-      case "error":
-      case "messageerror": {
-        return wrapped(errorEventHandler, listener);
-      }
-
-      case "message": {
-        return wrapped(messageEventHandler, listener);
-      }
-
-      default: {
-        return wrapped(customEventHandler, listener);
-      }
-    }
-  }
-
-  function EventClass(eventName) {
-    if (eventName === "error" || eventName === "messageerror") {
-      return ErrorEvent;
-    }
-
-    return MessageEvent;
-  }
-
-  // EventTarget dedupes on (type, callback), so in node the FIRST registration of
-  // a listener wins outright -- including its once-ness -- and later adds of the
-  // same function are no-ops. Keying wrappers per listener reproduces that.
-  function register(target, event, listener, wrapper, options) {
-    const map = registryFor(target, true)!;
-    let byListener = map.get(event);
-    if (!byListener) map.set(event, (byListener = new SafeMap()));
-    if (byListener.has(listener)) return false;
-    target.addEventListener(event, wrapper, options);
-    byListener.set(listener, wrapper);
-    return true;
-  }
-
-  function on(event, listener) {
-    register(this, event, listener, functionForEventType(event, listener), undefined);
-    return this;
-  }
-
-  function off(event, listener) {
-    if (listener) {
-      const byListener = registryFor(this, false)?.get(event);
-      const wrapper = byListener?.get(listener) ?? listener;
-      this.removeEventListener(event, wrapper);
-      byListener?.delete(listener);
-    } else {
-      this.removeEventListener(event);
-    }
-    return this;
-  }
-
-  function once(event, listener) {
-    const wrapper = functionForEventType(event, listener);
-    const target = this;
-    // EventTarget drops a {once:true} listener natively, without telling the
-    // registry — so purge it here or listenerCount()/eventNames() keep counting
-    // a listener that already fired.
-    function onceWrapper(ev) {
-      registryFor(target, false)?.get(event)?.delete(listener);
-      return wrapper(ev);
-    }
-    register(this, event, listener, onceWrapper, { once: true });
-    return this;
-  }
-
-  function emit(event, ...args) {
-    switch (event) {
-      case "error":
-      case "messageerror":
-      case "message":
-        this.dispatchEvent(new (EventClass(event))(event, ...args));
-        break;
-      default:
-        // Non-standard events surface as CustomEvent (detail = first arg) to
-        // addEventListener and as the raw argument to .on(), matching node.
-        this.dispatchEvent(new CustomEvent(event, { detail: args[0] }));
-        break;
-    }
-    return this;
-  }
-
-  const kMaxListeners = Symbol("kMaxListeners");
-  function setMaxListeners(n) {
-    this[kMaxListeners] = n;
-    return this;
-  }
-  function getMaxListeners() {
-    return this[kMaxListeners] ?? 10;
-  }
-  function listenerCount(type) {
-    return registryFor(this, false)?.get(type)?.size ?? 0;
-  }
-  function eventNames() {
-    const map = registryFor(this, false);
-    if (!map) return [];
-    const out: string[] = [];
-    for (const [k, v] of map) if (v.size > 0) out.push(k);
-    return out;
-  }
-  function removeAllListeners(type) {
-    const map = registryFor(this, false);
-    if (!map) return this;
-    const removeType = t => {
-      const byListener = map.get(t);
-      if (byListener) {
-        for (const w of byListener.values()) this.removeEventListener(t, w);
-        map.delete(t);
-      }
-    };
-    if (arguments.length === 0) {
-      // removeType only deletes `t`, and a Map iterator tolerates deleting the
-      // entry it just yielded — so no snapshot copy is needed here.
-      for (const t of map.keys()) removeType(t);
-    } else {
-      removeType(type);
-    }
-    return this;
-  }
-
-  // node inherits these from NodeEventTarget.prototype (a curated subset of
-  // EventEmitter, not EventEmitter itself); use an intermediate prototype so
-  // Object.getOwnPropertyNames(MessagePort.prototype) matches node.
-  const proto = Class.prototype;
-  const inherited = Object.create(Object.getPrototypeOf(proto));
-  const emitterMethods: [string, Function][] = [
-    ["on", on],
-    ["off", off],
-    ["once", once],
-    ["emit", emit],
-    ["addListener", on],
-    ["removeListener", off],
-    ["listenerCount", listenerCount],
-    ["eventNames", eventNames],
-    ["removeAllListeners", removeAllListeners],
-    ["setMaxListeners", setMaxListeners],
-    ["getMaxListeners", getMaxListeners],
-  ];
-  for (const [methodName, value] of emitterMethods) {
-    Object.defineProperty(inherited, methodName, { value, writable: true, enumerable: false, configurable: true });
-  }
-  Object.setPrototypeOf(proto, inherited);
-}
-
 const _MessagePort = globalThis.MessagePort;
-injectFakeEmitter(_MessagePort);
-
 const MessagePort = _MessagePort;
 
 // node's close(cb) registers cb as a one-time "close" listener before the native close.
@@ -810,19 +628,93 @@ function fakeParentPort() {
     value: self.addEventListener.bind(self),
   });
 
+  // MessagePort.prototype.on/etc. require a real MessagePort receiver; shadow
+  // them so calls on this stand-in forward to the global scope. A local map
+  // tracks which listeners were added via parentPort so listenerCount/
+  // eventNames/removeAllListeners see only those (self may carry internal
+  // listeners the user must not touch).
+  const byType = new SafeMap();
   Object.defineProperty(fake, "removeEventListener", {
-    value: self.removeEventListener.bind(self),
-  });
-
-  Object.defineProperty(fake, "removeListener", {
-    value: self.removeEventListener.bind(self),
-    enumerable: false,
-  });
-
-  Object.defineProperty(fake, "addListener", {
-    value: self.addEventListener.bind(self),
-    enumerable: false,
+    value(type: string, listener: any, options?: any) {
+      const set = byType.get(type);
+      self.removeEventListener(type, set?.get(listener) ?? listener, options);
+      set?.delete(listener);
+    },
   });
+  function track(type: string, listener: any, registered: any) {
+    let set = byType.get(type);
+    if (!set) byType.set(type, (set = new SafeMap()));
+    // First registration of a given listener wins (including its once-ness),
+    // matching node's NodeEventTarget dedup.
+    if (set.has(listener)) return false;
+    set.set(listener, registered);
+    return true;
+  }
+  function on(this: any, type: string, listener: any) {
+    if (track(type, listener, listener))
+      self.addEventListener(type, listener, { $kIsNodeStyleListener: true } as AddEventListenerOptions);
+    return this;
+  }
+  function once(this: any, type: string, listener: any) {
+    const wrapper = (arg: any) => {
+      byType.get(type)?.delete(listener);
+      return listener(arg);
+    };
+    if (track(type, listener, wrapper))
+      self.addEventListener(type, wrapper, { once: true, $kIsNodeStyleListener: true } as AddEventListenerOptions);
+    return this;
+  }
+  function off(this: any, type: string, listener: any) {
+    const set = byType.get(type);
+    self.removeEventListener(type, set?.get(listener) ?? listener);
+    set?.delete(listener);
+    return this;
+  }
+  function listenerCount(type: string) {
+    return byType.get(type)?.size ?? 0;
+  }
+  function eventNames() {
+    const out: string[] = [];
+    for (const [k, v] of byType) if (v.size > 0) out.push(k);
+    return out;
+  }
+  function removeAllListeners(this: any, type?: string) {
+    const clear = (t: string) => {
+      const set = byType.get(t);
+      if (set) {
+        for (const registered of set.values()) self.removeEventListener(t, registered);
+        byType.delete(t);
+      }
+    };
+    if (arguments.length === 0) for (const t of byType.keys()) clear(t);
+    else clear(type!);
+    return this;
+  }
+  function emit(type: string, arg?: any) {
+    const had = (byType.get(type)?.size ?? 0) > 0;
+    const ev =
+      type === "message" || type === "messageerror"
+        ? new MessageEvent(type, { data: arg })
+        : new CustomEvent(type, { detail: arg });
+    self.dispatchEvent(ev);
+    return had;
+  }
+  let maxListeners = 10;
+  for (const [name, fn] of [
+    ["on", on],
+    ["addListener", on],
+    ["once", once],
+    ["off", off],
+    ["removeListener", off],
+    ["listenerCount", listenerCount],
+    ["eventNames", eventNames],
+    ["removeAllListeners", removeAllListeners],
+    ["emit", emit],
+    ["getMaxListeners", () => maxListeners],
+    ["setMaxListeners", n => ((maxListeners = n), fake)],
+  ] as const) {
+    Object.defineProperty(fake, name, { value: fn, enumerable: false, configurable: true, writable: true });
+  }
 
   return fake;
 }

src/jsc/bindings/webcore/AddEventListenerOptions.h

@@ -48,6 +48,11 @@ struct AddEventListenerOptions : EventListenerOptions {
     // modules, mirroring Node.js's kResistStopPropagation: a listener registered
     // with it still runs after another listener called stopImmediatePropagation().
     bool resistStopPropagation { false };
+
+    // Not part of the DOM standard. Mirrors Node.js's kIsNodeStyleListener: when
+    // set, the listener is invoked with the event's underlying value (data/detail/
+    // error) instead of the Event wrapper. MessagePort.prototype.on/.once set it.
+    bool isNodeStyleListener { false };
 };
 
 } // namespace WebCore

src/jsc/bindings/webcore/EventFactory.cpp

@@ -88,8 +88,8 @@ JSC::JSValue toJSNewlyCreated(JSC::JSGlobalObject*, JSDOMGlobalObject* globalObj
     }
     //     case CompositionEventInterfaceType:
     //         return createWrapper<CompositionEvent>(globalObject, WTF::move(impl));
-    //     case CustomEventInterfaceType:
-    //         return createWrapper<CustomEvent>(globalObject, WTF::move(impl));
+    case CustomEventInterfaceType:
+        return createWrapper<CustomEvent>(globalObject, WTF::move(impl));
     // #if ENABLE(DEVICE_ORIENTATION)
     //     case DeviceMotionEventInterfaceType:
     //         return createWrapper<DeviceMotionEvent>(globalObject, WTF::move(impl));

src/jsc/bindings/webcore/EventHeaders.h

@@ -78,8 +78,8 @@
 #include "JSCloseEvent.h"
 // #include "CompositionEvent.h"
 // #include "JSCompositionEvent.h"
-// #include "CustomEvent.h"
-// #include "JSCustomEvent.h"
+#include "CustomEvent.h"
+#include "JSCustomEvent.h"
 // #if ENABLE(DEVICE_ORIENTATION)
 // #include "DeviceMotionEvent.h"
 // #include "JSDeviceMotionEvent.h"

src/jsc/bindings/webcore/EventListener.h

@@ -52,6 +52,9 @@ class EventListener : public RefCounted<EventListener>, public CanMakeWeakPtr<Ev
     virtual ~EventListener() = default;
     virtual bool operator==(const EventListener&) const = 0;
     virtual void handleEvent(ScriptExecutionContext&, Event&) = 0;
+    // For listeners registered with kIsNodeStyleListener; JSEventListener
+    // overrides this to pass the event's carried value (.data/.detail/.error).
+    virtual void handleEventNodeStyle(ScriptExecutionContext& ctx, Event& event) { handleEvent(ctx, event); }
 
     virtual void visitJSFunction(JSC::AbstractSlotVisitor&) {}
     virtual void visitJSFunction(JSC::SlotVisitor&) {}

src/jsc/bindings/webcore/EventListenerMap.cpp

@@ -163,6 +163,23 @@ bool EventListenerMap::remove(const AtomString& eventType, EventListener& listen
     return false;
 }
 
+bool EventListenerMap::removeAll(const AtomString& eventType)
+{
+    releaseAssertOrSetThreadUID();
+    Locker locker { m_lock };
+
+    for (unsigned i = 0; i < m_entries.size(); ++i) {
+        if (m_entries[i].first == eventType) {
+            for (auto& listener : m_entries[i].second)
+                listener->markAsRemoved();
+            m_entries.removeAt(i);
+            return true;
+        }
+    }
+
+    return false;
+}
+
 EventListenerVector* EventListenerMap::find(const AtomString& eventType)
 {
     for (auto& entry : m_entries) {

src/jsc/bindings/webcore/EventListenerMap.h

@@ -61,6 +61,7 @@ class EventListenerMap {
     void replace(const AtomString& eventType, EventListener& oldListener, Ref<EventListener>&& newListener, const RegisteredEventListener::Options&);
     RegisteredEventListener* add(const AtomString& eventType, Ref<EventListener>&&, const RegisteredEventListener::Options&);
     bool remove(const AtomString& eventType, EventListener&, bool useCapture);
+    bool removeAll(const AtomString& eventType);
     WEBCORE_EXPORT EventListenerVector* find(const AtomString& eventType);
     const EventListenerVector* find(const AtomString& eventType) const { return const_cast<EventListenerMap*>(this)->find(eventType); }
     Vector<AtomString> eventTypes() const;