From 0b2fea2575652b083f7795721f258029369a6a08 Mon Sep 17 00:00:00 2001
From: Thomas Heigl <thomas.heigl@gmail.com>
Date: Fri, 3 Sep 2021 13:13:39 +0200
Subject: [PATCH] #851 Ensure that `CompatibleFieldSerializer` sets fields with
 default values to `null`

---
 .../CompatibleFieldSerializer.java            | 11 ++++++
 .../CompatibleFieldSerializerTest.java        | 39 +++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/src/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializer.java b/src/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializer.java
index 3c58e2d3d..a57a79998 100644
--- a/src/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializer.java
+++ b/src/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializer.java
@@ -142,6 +142,7 @@ public T read (Kryo kryo, Input input, Class<? extends T> type) {
 					continue;
 				}
 				if (registration == null) {
+					setFieldToNull(cachedField, object);
 					if (chunked) inputChunked.nextChunk();
 					continue;
 				}
@@ -242,6 +243,16 @@ else if (compare > 0)
 		return fields;
 	}
 
+	private void setFieldToNull (CachedField field, Object obj) {
+		if (field instanceof ReflectField && field.getCanBeNull()) {
+			try {
+				((ReflectField)field).set(obj, null);
+			} catch (IllegalAccessException e) {
+				throw new KryoException("Error accessing field: " + field, e);
+			}
+		}
+	}
+
 	public CompatibleFieldSerializerConfig getCompatibleFieldSerializerConfig () {
 		return config;
 	}
diff --git a/test/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializerTest.java b/test/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializerTest.java
index 528bf3f14..48f3e684c 100644
--- a/test/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializerTest.java
+++ b/test/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializerTest.java
@@ -515,6 +515,20 @@ void testClassWithGenericField () {
 		roundTrip(9, new ClassWithGenericField<>(1));
 	}
 
+	// https://github.com/EsotericSoftware/kryo/issues/851
+	@Test
+	void testClassWithDefaultValueField () {
+		CompatibleFieldSerializer.CompatibleFieldSerializerConfig config = new CompatibleFieldSerializer.CompatibleFieldSerializerConfig();
+		config.setChunkedEncoding(true);
+		config.setReadUnknownFieldData(true);
+		kryo.setDefaultSerializer(new CompatibleFieldSerializerFactory(config));
+		kryo.register(ClassWithDefaultValueField.class);
+
+		final ClassWithDefaultValueField o = new ClassWithDefaultValueField();
+		o.setValue(null);
+		roundTrip(10, o);
+	}
+
 	public static class TestClass {
 		public String text = "something";
 		public int moo = 120;
@@ -811,4 +825,29 @@ public boolean equals (Object o) {
 			return Objects.equals(value, that.value);
 		}
 	}
+
+	public static class ClassWithDefaultValueField {
+
+		private Integer value = 10;
+
+		public Integer getValue () {
+			return value;
+		}
+
+		public void setValue (Integer value) {
+			this.value = value;
+		}
+
+		@Override
+		public boolean equals (Object o) {
+			if (this == o) {
+				return true;
+			}
+			if (o == null || getClass() != o.getClass()) {
+				return false;
+			}
+			final ClassWithDefaultValueField that = (ClassWithDefaultValueField)o;
+			return Objects.equals(value, that.value);
+		}
+	}
 }