From 167e99b9a16645e2cf2ad9b2495e47211064a551 Mon Sep 17 00:00:00 2001
From: Anatoli Papirovski <apapirovski@mac.com>
Date: Thu, 25 Oct 2018 04:02:23 -0700
Subject: [PATCH] timers: fix priority queue removeAt fn

PR-URL: https://github.com/nodejs/node/pull/23870
Fixes: https://github.com/nodejs/node/issues/23860
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 lib/internal/priority_queue.js       |  7 +++++-
 test/parallel/test-priority-queue.js | 36 ++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/lib/internal/priority_queue.js b/lib/internal/priority_queue.js
index cb046507a667d9..2f1db934b43cc8 100644
--- a/lib/internal/priority_queue.js
+++ b/lib/internal/priority_queue.js
@@ -83,8 +83,13 @@ module.exports = class PriorityQueue {
     heap[pos] = heap[size + 1];
     heap[size + 1] = undefined;
 
-    if (size > 0)
+    if (size > 0) {
+      // If not removing the last item, update the shifted item's position.
+      if (pos <= size && this[kSetPosition] !== undefined)
+        this[kSetPosition](heap[pos], pos);
+
       this.percolateDown(1);
+    }
   }
 
   remove(value) {
diff --git a/test/parallel/test-priority-queue.js b/test/parallel/test-priority-queue.js
index 5b8f53a1766bb5..702b5528ba9611 100644
--- a/test/parallel/test-priority-queue.js
+++ b/test/parallel/test-priority-queue.js
@@ -95,3 +95,39 @@ const PriorityQueue = require('internal/priority_queue');
 
   assert.strictEqual(queue.peek(), undefined);
 }
+
+{
+  const queue = new PriorityQueue((a, b) => {
+    return a.value - b.value;
+  }, (node, pos) => (node.position = pos));
+
+  queue.insert({ value: 1, position: null });
+  queue.insert({ value: 2, position: null });
+  queue.insert({ value: 3, position: null });
+  queue.insert({ value: 4, position: null });
+  queue.insert({ value: 5, position: null });
+
+  queue.insert({ value: 2, position: null });
+  const secondLargest = { value: 10, position: null };
+  queue.insert(secondLargest);
+  const largest = { value: 15, position: null };
+  queue.insert(largest);
+
+  queue.removeAt(5);
+  assert.strictEqual(largest.position, 5);
+
+  // check that removing 2nd to last item works fine
+  queue.removeAt(6);
+  assert.strictEqual(secondLargest.position, 6);
+
+  // check that removing the last item doesn't throw
+  queue.removeAt(6);
+
+  assert.strictEqual(queue.shift().value, 1);
+  assert.strictEqual(queue.shift().value, 2);
+  assert.strictEqual(queue.shift().value, 2);
+  assert.strictEqual(queue.shift().value, 4);
+  assert.strictEqual(queue.shift().value, 15);
+
+  assert.strictEqual(queue.shift(), undefined);
+}