quic: fix endpointClose error handling, document

PR-URL: #34283
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: jasnell

doc/api/quic.md

@@ -1354,6 +1354,21 @@ Emitted after the `QuicSocket` has been destroyed and is no longer usable.
 
 The `'close'` event will not be emitted multiple times.
 
+#### Event: `'endpointClose'`
+<!-- YAML
+added: REPLACEME
+-->
+
+Emitted after a `QuicEndpoint` associated witht the `QuicSocket` closes and
+has been destroyed. The handler will be invoked with two arguments:
+
+* `endpoint` {QuicEndpoint} The `QuicEndpoint` that has been destroyed.
+* `error` {Error} An `Error` object if the `QuicEndpoint` was destroyed because
+  of an error.
+
+When all of the `QuicEndpoint` instances associated with a `QuicSocket` have
+closed, the `QuicEndpoint` will also automatically close.
+
 #### Event: `'error'`
 <!-- YAML
 added: REPLACEME

lib/internal/quic/core.js

@@ -1056,12 +1056,17 @@ class QuicSocket extends EventEmitter {
   [kEndpointClose](endpoint, error) {
     const state = this[kInternalState];
     state.endpoints.delete(endpoint);
-    process.nextTick(emit.bind(this, 'endpointClose', endpoint, error));
+    process.nextTick(() => {
+      try {
+        this.emit('endpointClose', endpoint, error);
+      } catch (error) {
+        this.destroy(error);
+      }
+    });
 
     // If there are no more QuicEndpoints, the QuicSocket is no
     // longer usable.
     if (state.endpoints.size === 0) {
-      // Ensure that there are absolutely no additional sessions
       for (const session of state.sessions)
         session.destroy(error);
 

test/parallel/test-quic-client-server.js

@@ -222,6 +222,8 @@ server.on('ready', common.mustCall(() => {
   client = createQuicSocket({ client: { key, cert, ca, alpn: kALPN }
   });
 
+  client.on('endpointClose', common.mustCall());
+
   client.on('close', common.mustCall(() => {
     debug('Client closing. Duration', client.duration);
     debug('  Bound duration',