timers: fix priority queue removeAt fn

PR-URL: #23870
Fixes: #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

@@ -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) {

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);
+}