From b75ae5e0ac3842b9761bcf18671c99960230eb74 Mon Sep 17 00:00:00 2001
From: Thomas Heigl <thomas.heigl@gmail.com>
Date: Wed, 10 Nov 2021 17:43:13 +0100
Subject: [PATCH] #865 Ensure empty `PriorityQueue` can be deserialized (#866)

---
 .../kryo/serializers/DefaultSerializers.java  |  5 +-
 .../serializers/DefaultSerializersTest.java   | 61 +++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/src/com/esotericsoftware/kryo/serializers/DefaultSerializers.java b/src/com/esotericsoftware/kryo/serializers/DefaultSerializers.java
index ae2d36b5a..d9768a638 100644
--- a/src/com/esotericsoftware/kryo/serializers/DefaultSerializers.java
+++ b/src/com/esotericsoftware/kryo/serializers/DefaultSerializers.java
@@ -743,7 +743,8 @@ protected PriorityQueue createCopy (Kryo kryo, PriorityQueue original) {
 		}
 
 		private PriorityQueue createPriorityQueue (Class<? extends Collection> type, int size, Comparator comparator) {
-			if (type == PriorityQueue.class || type == null) return new PriorityQueue(size, comparator);
+			final int initialCapacity = Math.max(size, 1);
+			if (type == PriorityQueue.class || type == null) return new PriorityQueue(initialCapacity, comparator);
 			// Use reflection for subclasses.
 			try {
 				Constructor constructor = type.getConstructor(int.class, Comparator.class);
@@ -753,7 +754,7 @@ private PriorityQueue createPriorityQueue (Class<? extends Collection> type, int
 					} catch (SecurityException ignored) {
 					}
 				}
-				return (PriorityQueue)constructor.newInstance(comparator);
+				return (PriorityQueue)constructor.newInstance(initialCapacity, comparator);
 			} catch (Exception ex) {
 				throw new KryoException(ex);
 			}
diff --git a/test/com/esotericsoftware/kryo/serializers/DefaultSerializersTest.java b/test/com/esotericsoftware/kryo/serializers/DefaultSerializersTest.java
index f77c43611..6b0318da4 100644
--- a/test/com/esotericsoftware/kryo/serializers/DefaultSerializersTest.java
+++ b/test/com/esotericsoftware/kryo/serializers/DefaultSerializersTest.java
@@ -340,6 +340,42 @@ public int compare (Integer o1, Integer o2) {
 		assertEquals(queue.peek(), copy.peek());
 	}
 
+	@Test
+	void testPriorityQueue () {
+		List<Integer> values = Arrays.asList(7, 0, 5, 123, 432);
+		PriorityQueue<Integer> queue = new PriorityQueue(3, new IntegerComparator());
+		queue.addAll(values);
+
+		kryo.register(PriorityQueue.class);
+		kryo.register(IntegerComparator.class);
+		roundTrip(12, queue);
+	}
+
+	@Test
+	void testPriorityQueueSubclass () {
+		List<Integer> values = Arrays.asList(7, 0, 5, 123, 432);
+		PriorityQueue<Integer> queue = new PriorityQueueSubclass(3, new IntegerComparator());
+		queue.addAll(values);
+
+		kryo.register(PriorityQueueSubclass.class);
+		kryo.register(IntegerComparator.class);
+		roundTrip(12, queue);
+	}
+
+	@Test
+	void testEmptyPriorityQueue () {
+		PriorityQueue<Integer> queue = new PriorityQueue();
+		kryo.register(PriorityQueue.class);
+		roundTrip(3, queue);
+	}
+
+	@Test
+	void testEmptyPriorityQueueSubclass () {
+		PriorityQueue<Integer> queue = new PriorityQueueSubclass();
+		kryo.register(PriorityQueueSubclass.class);
+		roundTrip(3, queue);
+	}
+
 	@Test
 	void testCalendar () {
 		kryo.setRegistrationRequired(false);
@@ -467,6 +503,17 @@ void testURLSerializer () throws Exception {
 		roundTrip(78, new URL("https://github.com:443/EsotericSoftware/kryo/pulls?utf8=%E2%9C%93&q=is%3Apr"));
 	}
 
+	protected void doAssertEquals(Object object1, Object object2) {
+		if (object1 instanceof PriorityQueue && object2 instanceof PriorityQueue) {
+			final PriorityQueue q1 = (PriorityQueue) object1;
+			final PriorityQueue q2 = (PriorityQueue) object2;
+			super.doAssertEquals(q1.peek(), q2.peek());	
+			super.doAssertEquals(q1.toArray(), q2.toArray());	
+		} else {
+			super.doAssertEquals(object1, object2);
+		}
+	}
+
 	public enum TestEnum {
 		a, b, c
 	}
@@ -500,4 +547,18 @@ public BigIntegerSubclass (String val) {
 		}
 	}
 
+	static class PriorityQueueSubclass extends PriorityQueue {
+		public PriorityQueueSubclass() {
+		}
+
+		public PriorityQueueSubclass(int initialCapacity, Comparator comparator) {
+			super(initialCapacity, comparator);
+		}
+	}
+
+	static class IntegerComparator implements Comparator<Integer> {
+		public int compare(Integer o1, Integer o2) {
+			return o2 - o1;
+		}
+	}
 }