#851 Ensure that CompatibleFieldSerializer sets fields with default values to null

src/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializer.java

@@ -142,6 +142,12 @@ public T read (Kryo kryo, Input input, Class<? extends T> type) {
 					continue;
 				}
 				if (registration == null) {
+					try {
+						if (cachedField != null && cachedField.canBeNull) {
+							cachedField.field.set(object, null);
+						}
+					} catch (IllegalAccessException e) {
+					}
 					if (chunked) inputChunked.nextChunk();
 					continue;
 				}

test/com/esotericsoftware/kryo/serializers/CompatibleFieldSerializerTest.java

@@ -513,6 +513,20 @@ 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;
@@ -809,4 +823,29 @@ 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);
+		}
+	}
 }