`@JsonValue` fails for Java Record

[cowwoc]

Version information
2.12.1
OpenJDK 15.0.1

To Reproduce

Given:

public final record GetLocations(@JsonValue Map<String, URI> nameToLocation)
{
	@JsonCreator
	public GetLocations(Map<String, URI> nameToLocation)
	{
		assertThat(nameToLocation, "nameToLocation").isNotNull();
		this.nameToLocation = new HashMap<>(nameToLocation);
	}
}

I am expecting Jackson to serialize the Map to JSON but instead I get the following exception:

Problem with definition of [AnnotedClass GetLocations]: Multiple 'as-value' properties defined ([field GetLocations#nameToLocation] vs [method GetLocations#nameToLocation()])

[cowwoc]

Adding the following code works around the problem (though ideologically, I'd prefer to serialize the return value of the getter than the field):

@JsonValue(false)
@Override
public Map<String, URI> nameToLocation()
{
	return nameToLocation;
}

[cowtowncoder]

Very likely related to the general issue (hoped to be tackled in 2.13) of matching @JsonCreator (constructor) parameters to fields, so that effectively @JsonValue would be invisible to property handling logic.

On plus side, if so, would get solved along with quite a few other problems.

[pjfanning]

@cowtowncoder if I read this issue correctly, then this appears to be similar to an issue in Scala. Java Records are similar to Scala Case Classes. In a Case Class, the constructor params are automatically accessible publicly - essentially Scala compiler creates a scala class with a field and a method with the name of the field. Annotations are added to the field unless you use a special form of the annotation (@(JsonValue @getter) is an annotation that is added to the derived getter method instead of the field). Scala 3 has a bug where the @getter is ignored so the annotation is not treated correctly.

So the ask on my part, is would it be possible to have jackson-databind PojoPropertiesCollector look for @JsonValue annotations on methods and fields?

[cowtowncoder]

@pjfanning I think this would be part of the big rewrite of Creator-vs-Properties introspection that I was hoping to do for 2.13 but did not have time for. So got pushed forward.

Handling of @JsonValue should be synchronized in a way that avoids any issues with property detection, in case of serialization, yes. Where exactly that should be rectified I am not sure.

One thing that might be help would be reproducing this with regular @JsonCreator-using POJO instead of Record (assuming this is possible). Records have some special handling but this might not be due to that but more general issue.

[pjfanning]

@cowtowncoder thanks for the update.

My comment above was really an enhancement request so that @JsonValue annotations could be supported on fields - would this be feasible?

[cowtowncoder]

They are already, since Jackson 2.9 (see #1428).

[pjfanning]

thanks @cowtowncoder - must be something else going on that is causing the scala 3 stuff not to work