EnumSet deserialization does not work when we activate default typing in ObjectMapper

[dvhvsekhar]

Search before asking

• I searched in the issues and found nothing similar.

Describe the bug

If we serialize an object which has a property of type Set, but referring EnumSet at runtime, then serialization uses CollectionSerializer instead of EnumSetSerializer for this property, when we activate default typing in ObjectMapper. This causes deserialization (using EnumSetDeserializer) to fail, since EnumSetDeserializer expects encoding of EnumSetSerializer, but not of CollectionSerializer.

Version Information

2.14.0 and above

Reproduction

If we run the below given test (java code), we get following error:

[ERROR] EnumSetSerializationTest.testSerialization:69 » MismatchedInput Cannot deserialize value of type com.fasterxml.jackson.databind.ser.enums.EnumSetSerializationTest$MyEnum from Array value (token JsonToken.START_ARRAY)
at [Source: REDACTED (StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION disabled); line: 1, column: 191] (through reference chain: com.fasterxml.jackson.databind.ser.enums.EnumSetSerializationTest$EnumSetHolder["enumSet"]->java.util.RegularEnumSet[0])

package com.fasterxml.jackson.databind.ser.enums;

import com.fasterxml.jackson.databind.BaseMapTest;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.EnumSet;
import java.util.Set;

import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper.DefaultTyping;
import com.fasterxml.jackson.databind.jsontype.BasicPolymorphicTypeValidator;

public class EnumSetSerializationTest extends BaseMapTest {

	static enum MyEnum {
		ITEM_A, ITEM_B;
	}

	static class EnumSetHolder {
		private Set<MyEnum> enumSet; // use Set instead of EnumSet for type of this

		public Set<MyEnum> getEnumSet() {
			return enumSet;
		}

		public void setEnumSet(Set<MyEnum> enumSet) {
			this.enumSet = enumSet;
		}

		@Override
		public boolean equals(Object o) {
			if (!(o instanceof EnumSetHolder)) {
				return false;
			}
			EnumSetHolder eh = (EnumSetHolder) o;
			if (eh == this) {
				return true;
			}
			if (enumSet == null) {
				if (eh.getEnumSet() == null) {
					return true;
				} else {
					return false;
				}
			} else {
				if (eh.getEnumSet() == null) {
					return false;
				}
				return enumSet.containsAll(eh.getEnumSet());
			}
		}
	}

	public void testSerialization() throws Exception {
		ObjectMapper mapper = jsonMapperBuilder().build()
				.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
				// this type information is needed in json string, for this test
				.activateDefaultTyping(BasicPolymorphicTypeValidator.builder().allowIfBaseType(Object.class).build(),
						DefaultTyping.EVERYTHING);

		EnumSetHolder enumSetHolder = new EnumSetHolder();
		enumSetHolder.setEnumSet(EnumSet.allOf(MyEnum.class));
		String jsonStr = mapper.writeValueAsString(enumSetHolder);
		EnumSetHolder result = mapper.readValue(jsonStr, EnumSetHolder.class);
		assertEquals(result, enumSetHolder);
	}
}

Expected behavior

Above given test code should pass.

Additional context

As a workaround, if we make type of EnumSetHolder#enumSet property as EnumSet instead of Set, in the above given code, test passes.

No response

[dvhvsekhar]

I proposed a fix with PR - #4215

[cowtowncoder]

Ok, now we have a reproduction at least. Looks like Enums do not handle polymorphic deserialization well at this point -- probably since expectation wasn't that they'd ever be polymorphic.
Before addition of DefaultTyping.EVERYTHING...
(I did change test to use new DefaultTyping.NON_FINAL_AND_ENUMS which fails similarly, fwtw)

[cowtowncoder]

Ok, actually, it's not so much EnumDeserializer that is not playing nicely, but rather EnumSetDeserializer... since that would have to create and use TypeDeserializer for Enum values.
This is what basic CollectionDeserializer does.

I don't know if I have time to work much more on this issue but if anyone wants to try to figure it out would be happy to review PR.

[cowtowncoder]

Ok, one more note: it looks like BasicDeserializerFactory already has TypeDeserializer to pass when constructing EnumSetDeserializer. So maybe I might be able to provide a fix. Fix though will probably need to go in 2.17 since (minor) internal API change needed.
But fix seems quite doable.

[cowtowncoder]

Was able to fix; deprecated older methods, fix will be in 2.17.0.