From 883fc779b637732b18e2d0e6b1f386cebb37e93c Mon Sep 17 00:00:00 2001
From: James M Snell <jasnell@gmail.com>
Date: Mon, 24 Aug 2020 13:11:23 -0700
Subject: events: allow use of AbortController with once

Allows an AbortSignal to be passed in to events.once() to cancel
waiting on an event.

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/34911
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
---
 lib/events.js | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

(limited to 'lib/events.js')

diff --git a/lib/events.js b/lib/events.js
index 48341c0b20..270588fcbc 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -44,6 +44,7 @@ const kRejection = SymbolFor('nodejs.rejection');
 let spliceOne;
 
 const {
+  hideStackFrames,
   kEnhanceStackBeforeInspector,
   codes
 } = require('internal/errors');
@@ -57,9 +58,20 @@ const {
   inspect
 } = require('internal/util/inspect');
 
+const {
+  validateAbortSignal
+} = require('internal/validators');
+
 const kCapture = Symbol('kCapture');
 const kErrorMonitor = Symbol('events.errorMonitor');
 
+let DOMException;
+const lazyDOMException = hideStackFrames((message, name) => {
+  if (DOMException === undefined)
+    DOMException = internalBinding('messaging').DOMException;
+  return new DOMException(message, name);
+});
+
 function EventEmitter(opts) {
   EventEmitter.init.call(this, opts);
 }
@@ -621,22 +633,61 @@ function unwrapListeners(arr) {
   return ret;
 }
 
-function once(emitter, name) {
+async function once(emitter, name, options = {}) {
+  const signal = options ? options.signal : undefined;
+  validateAbortSignal(signal, 'options.signal');
+  if (signal && signal.aborted)
+    throw lazyDOMException('The operation was aborted', 'AbortError');
   return new Promise((resolve, reject) => {
     const errorListener = (err) => {
       emitter.removeListener(name, resolver);
+      if (signal != null) {
+        eventTargetAgnosticRemoveListener(
+          signal,
+          'abort',
+          abortListener,
+          { once: true });
+      }
       reject(err);
     };
     const resolver = (...args) => {
       if (typeof emitter.removeListener === 'function') {
         emitter.removeListener('error', errorListener);
       }
+      if (signal != null) {
+        eventTargetAgnosticRemoveListener(
+          signal,
+          'abort',
+          abortListener,
+          { once: true });
+      }
       resolve(args);
     };
     eventTargetAgnosticAddListener(emitter, name, resolver, { once: true });
     if (name !== 'error') {
       addErrorHandlerIfEventEmitter(emitter, errorListener, { once: true });
     }
+    function abortListener() {
+      if (typeof emitter.removeListener === 'function') {
+        emitter.removeListener(name, resolver);
+        emitter.removeListener('error', errorListener);
+      } else {
+        eventTargetAgnosticRemoveListener(
+          emitter,
+          name,
+          resolver,
+          { once: true });
+        eventTargetAgnosticRemoveListener(
+          emitter,
+          'error',
+          errorListener,
+          { once: true });
+      }
+      reject(lazyDOMException('The operation was aborted', 'AbortError'));
+    }
+    if (signal != null) {
+      signal.addEventListener('abort', abortListener, { once: true });
+    }
   });
 }
 
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