events: support event handlers on prototypes

PR-URL: #35931 Backport-PR-URL: #38386 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Daijiro Wachi <[email protected]> Reviewed-By: Rich Trott <[email protected]>

Author: benjamingr

lib/internal/event_target.js

@@ -13,6 +13,7 @@ const{
  Symbol,
  SymbolFor,
  SymbolToStringTag,
+ SafeWeakMap,
  SafeWeakSet,
 }=primordials;
 
@@ -576,21 +577,27 @@ function emitUnhandledRejectionOrErr(that, err, event){
 process.emit('error',err,event);
 }
 
+// A map of emitter -> map of name -> handler
+consteventHandlerValueMap=newSafeWeakMap();
+
 functiondefineEventHandler(emitter,name){
 // 8.1.5.1 Event handlers - basically `on[eventName]` attributes
-leteventHandlerValue;
-Object.defineProperty(emitter,`on${name}`,{
+ObjectDefineProperty(emitter,`on${name}`,{
 get(){
-returneventHandlerValue;
+returneventHandlerValueMap.get(this)?.get(name);
 },
 set(value){
-if(eventHandlerValue){
-emitter.removeEventListener(name,eventHandlerValue);
+constoldValue=eventHandlerValueMap.get(this)?.get(name);
+if(oldValue){
+this.removeEventListener(name,oldValue);
 }
 if(typeofvalue==='function'){
-emitter.addEventListener(name,value);
+this.addEventListener(name,value);
+}
+if(!eventHandlerValueMap.has(this)){
+eventHandlerValueMap.set(this,newMap());
 }
-eventHandlerValue=value;
+eventHandlerValueMap.get(this).set(name,value);
 },
 configurable: true,
 enumerable: true

lib/internal/worker/io.js

@@ -99,13 +99,14 @@ ObjectDefineProperty(
 // This is called from inside the `MessagePort` constructor.
 functiononinit(){
 initNodeEventTarget(this);
-// TODO(addaleax): This should be on MessagePort.prototype, but
-// defineEventHandler() does not support that.
 defineEventHandler(this,'message');
 defineEventHandler(this,'messageerror');
 setupPortReferencing(this,this,'message');
 }
 
+defineEventHandler(MessagePort.prototype,'message');
+defineEventHandler(MessagePort.prototype,'messageerror');
+
 ObjectDefineProperty(MessagePort.prototype,onInitSymbol,{
 enumerable: true,
 writable: false,

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

@@ -165,9 +165,7 @@ const{MessageChannel, MessagePort } = require('worker_threads');
 assert.deepStrictEqual(
 Object.getOwnPropertyNames(MessagePort.prototype).sort(),
 [
-// TODO(addaleax): This should include onmessage (and eventually
-// onmessageerror).
-'close','constructor','postMessage','ref','start',
-'unref'
+'close','constructor','onmessage','onmessageerror','postMessage',
+'ref','start','unref'
 ]);
 }