`Optional<JsonNode>` deserialization from "absent" value does not work in the expected way

jackson-datatype-jdk8 OptionalDeserializer から開始し、PropertyValueBuffer::_findMissing、JsonDeserializer#getAbsentValue、JsonNodeDeserializer#getNullValue を通じて欠落プロパティの処理を追跡します。{} からデシリアライズされた MyRecord の例の動作を確認し、存在しない Optional が NullNode をラップするのではなく空のままになることを確認します。プロジェクトに既存のテストで期待される結果を検証します。

Example:

public record MyRecord(
        Optional<JsonNode> myField
) {
}

When deserialized from: {}
Expected:
myField.isPresent() == false
Actual:
myField.isPresent() == true

This is because myField gets set to an Optional of a NullNode

After spending some time looking into the source code of both the jackson-databind and the jackson-datatype-jdk8 libraries, the problem seems to lie in the OptionalDeserializer (or higher).

During deserialization, when a property is missing, the PropertyValueBuffer::_findMissing method is called and in it, this piece of code is called:
https://github.com/FasterXML/jackson-databind/blob/0fe97e0d69b7d5362907b094d5b979bc2216dc4a/src/main/java/com/fasterxml/jackson/databind/deser/impl/PropertyValueBuffer.java#L203

            // Third: NullValueProvider? (22-Sep-2019, [databind#2458])
            // 08-Aug-2021, tatu: consider [databind#3214]; not null but "absent" value...
            Object absentValue = prop.getNullValueProvider().getAbsentValue(_context);
            if (absentValue != null) {
                return absentValue;
            }

The OptionalDeserializer is not overriding its inherited getAbsentValue method to return Optional.ofNullable(_valueDeserializer.getAbsentValue(ctxt)); (or similar).

Due to the lack of the overriding, the inherited getAbsentValue method actually calls getNullValue instead as can be seen here:
https://github.com/FasterXML/jackson-databind/blob/0fe97e0d69b7d5362907b094d5b979bc2216dc4a/src/main/java/com/fasterxml/jackson/databind/JsonDeserializer.java#L349

    @Override
    public Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
        return getNullValue(ctxt);
    }

In the case of a JsonNode, the JsonNodeDeserializer is used. This deserializer overrides the getNullValue method to return a NullNode.

https://github.com/FasterXML/jackson-databind/blob/0fe97e0d69b7d5362907b094d5b979bc2216dc4a/src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java#L73

    @Override
    public JsonNode getNullValue(DeserializationContext ctxt) {
        return ctxt.getNodeFactory().nullNode();
    }