Cannot Construct Subtype of Sealed Class

[skvariljan]

Search before asking

• I searched in the issues and found nothing similar.
• I have confirmed that the same problem is not reproduced if I exclude the KotlinModule.
• I searched in the issues of databind and other modules used and found nothing similar.
• I have confirmed that the problem does not reproduce in Java and only occurs when using Kotlin and KotlinModule.

Describe the bug

After upgrading from v2.17.2 to v2.18.1, we cannot parse sealed hierarchies annotated with @JsonTypeInfo anymore. The code in the example works in v2.17.2, but doesn't work in later versions and produces the following exception:
com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of ChildClass (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)

To Reproduce

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "_type")
sealed class BaseClass

data class ChildClass(val text: String) : BaseClass()

val json =
    """
        {
            "_type": "ChildClass",
            "text": "Test"
        }
    """

val jacksonObjectMapper = ObjectMapper().registerKotlinModule()
val message = jacksonObjectMapper.readValue<BaseClass>(json)

println(message is ChildClass)

Expected behavior

Prints true.

Versions

Kotlin:
Jackson-module-kotlin: 2.18.1
Jackson-databind: 2.18.1

Additional context

No response

[cowtowncoder]

One suggestion: this might be due to change in detection of "Creator" style (Delegating vs Property), and not polymorphic handling or sealed classes.
One way to fix this is so is by adding

@JsonCreator(mode = JsonCreator.Mode.DELEGATING)

to constructor (I forget how that is done with Kotlin -- @k163377 can help).

The change, if my hunch is correct, is because of how ambiguity of 1-property types is resolved -- this is heuristic and fundamentally ambiguous. But formerly (2.17) it seems that the case was deemed as Delegating (not recognizing text as property), but with property introspection rewrite in 2.18, as Property-based.

[cowtowncoder]

Very likely fixed by jackson-databind changes for 2.18.2, currently available via 2.18.2-SNAPSHOT.

[k163377]

I added a regression test based on the code submitted by @skvariljan and verified that it has been fixed.

[skvariljan]

This is great news, thank you.

[skvariljan]

I've tested my original example with v2.18.2 and it still throws the same exception. Can you re-open this issue, please?

[k163377]

@skvariljan
The following test succeeds on all branches after 2.18.
https://github.com/FasterXML/jackson-module-kotlin/blob/edf95928e3dc8293b4a78106d8720cfacdb6b12d/src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/github/GitHub844.kt

Can you please reproduce and submit a new issue as it is most likely some different problem?

[skvariljan]

Ok, thanks, we'll dig into this.