events: change EventTarget handler exception behavior

Change the behavior of EventTarget, instead of emitting
'error' on handler exception, emit 'uncaughtException'.

Fixes: #36770

PR-URL: #37237
Fixes: #36770
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Rich Trott <[email protected]>

Author: Nitzan Uziely

doc/api/events.md

@@ -1137,6 +1137,9 @@ setMaxListeners(5, target, emitter);
 <!-- YAML
 added: v14.5.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/37237
+    description: changed EventTarget error handling.
   - version: v15.4.0
     pr-url: https://github.com/nodejs/node/pull/35949
     description: No longer experimental.

lib/internal/event_target.js

@@ -459,9 +459,9 @@ class EventTarget {
           result = FunctionPrototypeCall(callback, this, arg);
         }
         if (result !== undefined && result !== null)
-          addCatch(this, result, createEvent());
+          addCatch(result);
       } catch (err) {
-        emitUnhandledRejectionOrErr(this, err, createEvent());
+        emitUncaughtException(err);
       }
 
       handler = next;
@@ -624,19 +624,19 @@ function isEventTarget(obj) {
   return obj?.constructor?.[kIsEventTarget];
 }
 
-function addCatch(that, promise, event) {
+function addCatch(promise) {
   const then = promise.then;
   if (typeof then === 'function') {
     FunctionPrototypeCall(then, promise, undefined, function(err) {
       // The callback is called with nextTick to avoid a follow-up
       // rejection from this promise.
-      process.nextTick(emitUnhandledRejectionOrErr, that, err, event);
+      emitUncaughtException(err);
     });
   }
 }
 
-function emitUnhandledRejectionOrErr(that, err, event) {
-  process.emit('error', err, event);
+function emitUncaughtException(err) {
+  process.nextTick(() => { throw err; });
 }
 
 function makeEventHandler(handler) {

test/parallel/test-eventtarget.js

@@ -178,14 +178,16 @@ let asyncTest = Promise.resolve();
 }
 
 {
-  const uncaughtException = common.mustCall((err, event) => {
+  const uncaughtException = common.mustCall((err, origin) => {
     strictEqual(err.message, 'boom');
-    strictEqual(event.type, 'foo');
+    strictEqual(origin, 'uncaughtException');
   }, 4);
 
-  // Whether or not the handler function is async or not, errors
-  // are routed to uncaughtException
-  process.on('error', uncaughtException);
+  // Make sure that we no longer call 'error' on error.
+  process.on('error', common.mustNotCall());
+  // Don't call rejection even for async handlers.
+  process.on('unhandledRejection', common.mustNotCall());
+  process.on('uncaughtException', uncaughtException);
 
   const eventTarget = new EventTarget();
 

test/parallel/test-process-uncaught-exception-monitor.js

@@ -55,15 +55,15 @@ process.on(
 process.on('uncaughtException', common.mustCall((err, origin) => {
   assert.strictEqual(origin, 'uncaughtException');
   assert.strictEqual(err, theErr);
-}));
 
-process.nextTick(common.mustCall(() => {
-  // Test with uncaughtExceptionCaptureCallback installed
-  process.setUncaughtExceptionCaptureCallback(common.mustCall(
-    (err) => assert.strictEqual(err, theErr))
-  );
+  process.nextTick(common.mustCall(() => {
+    // Test with uncaughtExceptionCaptureCallback installed
+    process.setUncaughtExceptionCaptureCallback(common.mustCall(
+      (err) => assert.strictEqual(err, theErr))
+    );
 
-  throw theErr;
+    throw theErr;
+  }));
 }));
 
 throw theErr;