External property polymorphic deserialization does not work with enums

[rocketraman]

versions: Jackson 2.8.1, Jackson-module-kotlin 2.8.1

Attempting to deserialize a class using external_property. In my case, the property is an Enum type with values matching the type name. Now that issue #999 is fixed, I thought this would work, but now I'm getting a different error:

Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of enum.Invite, problem: argument type mismatch
 at [Source: {
  "kind": "CONTACT",
  "to": {
    "name": "Foo"
  }
}; line: 6, column: 1]
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:268)
    at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1405)
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.wrapAsJsonMappingException(StdValueInstantiator.java:468)
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.rewrapCtorProblem(StdValueInstantiator.java:487)
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromObjectWith(StdValueInstantiator.java:276)
    at com.fasterxml.jackson.module.kotlin.KotlinValueInstantiator.createFromObjectWith(KotlinValueInstantiator.kt:30)
    at com.fasterxml.jackson.databind.deser.impl.PropertyBasedCreator.build(PropertyBasedCreator.java:135)
    at com.fasterxml.jackson.databind.deser.impl.ExternalTypeHandler.complete(ExternalTypeHandler.java:225)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeUsingPropertyBasedWithExternalTypeId(BeanDeserializer.java:937)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeWithExternalTypeId(BeanDeserializer.java:792)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:312)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2852)
    at enum.Reproduction_KindEnumKt.main(Reproduction-KindEnum.kt:49)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.IllegalArgumentException: argument type mismatch
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.fasterxml.jackson.databind.introspect.AnnotatedConstructor.call(AnnotatedConstructor.java:124)
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromObjectWith(StdValueInstantiator.java:274)
    ... 15 more

Process finished with exit code 1

Here is the reproduction recipe: https://github.com/rocketraman/jackson-issue-enum-polymorphism/blob/master/src/main/kotlin/enumtype/Reproduction-KindEnum.kt

[apatrida]

This one is odd, basically in the subclass of StdValueInstantiator in createFromObjectWith() function it receives in the buffer: PropertyValueBuffer parameter when calling buffer.getParameters(props) a first parameter of type String that is CONTACT and a second that is type InviteToContact that is correct and this is stored in local variablejsonParmValueList.

Then the KotlinValueInstantiator in this case just delegates to super.createFromObjectWith(ctxt, jsonParmValueList) which blows up with this exception, so it tries to create the object with the wrong datatype for the first parameter (String instead of the InviteKind enum) and causes this exception. That doesn't appear to be a problem in the Kotlin module which doesn't handle this case and just delegates. Although I think if it didn't it would blow up differently because it would still have the wrong type.

[apatrida]

So the bug is that the type of the polymorphic variable is coming in as String instead of the Enum type and therefore cannot be used to create the object, argument type mismatch to the constructor.

Fails when databind code does the instantiation, and when I have the kotlin module do the same, it fails as well.

Maybe only applies when ValueInstantiator is being used, or is that always used as StdValueInstantiator?

@cowtowncoder ??

[apatrida]

You can test by running the Kotlin module after re-enabling the test in:
https://github.com/FasterXML/jackson-module-kotlin/blob/master/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/GithubDatabind1328.kt

[cowtowncoder]

I would need a Java-only reproduction here, since it sounds there's nothing Kotlin-specific about it.

[cowtowncoder]

Or is this basically #1366?

[rocketraman]

@apatrida (cc: @cowtowncoder ) I was not able to reproduce this in Java. Here is the java repro attempt:

https://github.com/rocketraman/jackson-issue-enum-polymorphism/blob/master/src/main/java/enumtype/java/ReproductionKindEnum.java

[apatrida]

@rocketraman not sure, basically I receive a value of the wrong type (string) when it should be coerced to the enum value already.

It could still be an issue with the StdValueInstantiator... i'll check it again.

[apatrida]

@cowtowncoder The issue is StdValueInstantiator and is hard to reproduce in Java because the default constructor is called and then values are set after at which point they have the correct type. But if a value instantiator is in play, then this code will break:

 @Override public Object createFromObjectWith(DeserializationContext ctxt,
            SettableBeanProperty[] props, PropertyValueBuffer buffer) {
   Object[] jsonParmValueList = buffer.getParameters(props)
   super.createFromObjectWith(ctxt, jsonParmValueList)
}

and looking at the Object[] of parameters received it is because the enum comes as type String and not as an enum type. Whereas if this is set via a property (in @rocketraman attempt to reproduce in Java) then it comes as the enum type which doesn't crash.

So something in the PropertyValueBuffer class does not know what type to coerce the value into...

Looking at the method signature again... the SettableBeanProperty[] props parameter should have the properties with their correct types, right? And it does, I have 2 properties that come in as:

[simple type, class com.fasterxml.jackson.module.kotlin.test.GithubDatabind1328$InviteKind]
[simple type, class com.fasterxml.jackson.module.kotlin.test.GithubDatabind1328$InviteTo]

Great, those are correct. So why then does buffer.getParameters(props) return:

[0]  "CONTACT" as String
[1]   InviteToContact(name=Foo) as InviteToContact

Therefore buffer.getParameters in databind does not coerce the string "CONTACT" into an enum as it should. The issue lies there. Not sure how in Java you can force the StdValueInstantiator to be used to reproduce this.

[apatrida]

Looking at the work from #1224 would help to figure out how to reproduce this from Java since there were test cases written for this @rocketraman

[apatrida]

And it goes deeper, whatever created the PropertyValueBuffer instance put the wrong type in to begin with since _creatorParameters contains the string instead of enum as well.

[apatrida]

 public boolean assignParameter(SettableBeanProperty prop, Object value)
    {
        final int ix = prop.getCreatorIndex();
        _creatorParameters[ix] = value;    <------ VALUE IS WRONG TYPE, but `prop` is correct type
        ...

So the value passed into PropertyValueBuffer.assignParameter is wrong type.

who's job is it to coerce the type from a string into an enum @cowtowncoder ?

[apatrida]

I can work around the issue by special casing string => enum conversion but then the normal StdValueInstantiator will still fail, I'd only fix the Kotlin case.

[cowtowncoder]

@apatrida Ok hadn't noticed your second to last comment. I think I'd really need a smallish example to follow through, to know who is right, who wrong.

[pmorixe]

I have the same issue(I think its an issue) after upgrading from 2.7.4 -> 2.8.6 in Java spring-boot project
Using an Enum as EXTERNAL_PROPERTY, the instantiation of my polymorphic variable its right set but the type variable(Enum type) (that its correctly mapped) on object creation the args comes as String

My json
{ type:"A", obj: {...} }

public class MyObject {
	Type type;

	@JsonTypeInfo(property = "type", include = EXTERNAL_PROPERTY, use = NAME)
	@JsonSubTypes({
			@JsonSubTypes.Type(value = A.class,name = "A"),
			@JsonSubTypes.Type(value = B.class,name = "B")
        })
	Interface 	obj;
}

enum Type {
        A, B
}

class A implements Interface {
...
}
class B implements Interface {
...
}