Scala 2.12.0 compilation warning when using Jackson @JsonTypeInfo-annotation

[Morten Kjetland]

Hi,

The following code using Jackson 2.8.4 and Scala 2.12.0:

import com.fasterxml.jackson.annotation.JsonTypeInfo.{As, Id}
import com.fasterxml.jackson.annotation.{JsonSubTypes, JsonTypeInfo}

@JsonTypeInfo(
  use = JsonTypeInfo.Id.NAME,
  include = JsonTypeInfo.As.PROPERTY,
  property = "type")
@JsonSubTypes(Array(
  new Type(value = classOf[AddCfsRelation], name = "add"),
  new Type(value = classOf[RemoveCfsRelation], name = "remove")
))

trait MyTrait {
  def someProperty: String
}

Gives this compiler-warning:

[WARNING] warning: While parsing annotations in C:\path\MyTrait.class, could not find NAME in enum <none>.

[INFO] This is likely due to an implementation restriction: an annotation argument cannot refer to a member of the annotated class (SI-7014).

Here is the source of the annotation: https://github.com/FasterXML/jackson-annotations/blob/master/src/main/java/com/fasterxml/jackson/annotation/JsonTypeInfo.java

This was not an issue with Scala 2.11

Best regards,

Morten Kjetland

[Lukas Rytz]

Hi Morten

Thanks for the report. Could you provide exact instructions how to reproduce?

I put this on my classpath and changed your example a little, and it compiles without warnings for me:

import com.fasterxml.jackson.annotation.JsonTypeInfo.{As, Id}
import com.fasterxml.jackson.annotation.{JsonSubTypes, JsonTypeInfo}
import JsonSubTypes.Type // <<< added import

@JsonTypeInfo(
  use = JsonTypeInfo.Id.NAME,
  include = JsonTypeInfo.As.PROPERTY,
  property = "type")
@JsonSubTypes(Array(
  new Type(value = classOf[Object], name = "add"),   // <<< changed to Object
  new Type(value = classOf[Object], name = "remove") // <<< changed to Object
))
trait MyTrait {
  def someProperty: String
}

​

Thanks: Lukas

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[Morten Kjetland]

Thanks for looking into it.

I'm seeing the warning both when compiling in IntelliJ 2016.3 and with maven using this plugin:

<plugin>
    <groupId>net.alchim31.maven</groupId>
    <artifactId>scala-maven-plugin</artifactId>
    <version>3.2.0</version>
    <configuration>
        <scalaVersion>${scala.version}</scalaVersion>
        <args>
            <arg>-deprecation</arg>
            <arg>-feature</arg>
        </args>
    </configuration>
    <executions>
        <execution>
            <id>scala-compile-first</id>
            <phase>process-resources</phase>
            <goals>
                <goal>add-source</goal>
                <goal>compile</goal>
            </goals>
        </execution>
        <execution>
            <id>scala-test-compile</id>
            <phase>process-test-resources</phase>
            <goals>
                <goal>testCompile</goal>
            </goals>
        </execution>
        <execution>
            <id>attach-javadocs</id>
            <goals>
                <goal>doc-jar</goal>
            </goals>
        </execution>
    </executions>
</plugin>

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[Alan Stewart]

Hi,

I also see the same warnings using 2.12.1 and Jackson 2.8.4 with:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes(Array(
  new Type(value = classOf[TagObject], name = "tag"),
  new Type(value = classOf[CommitObject], name = "commit"),
  new Type(value = classOf[BlobObject], name = "blob")))
sealed trait TypedObject extends GitHubRef

and same compiler plugin configuration

[Jason Zaugg]

It would be a great help if you could produce a standalone project that we could clone to investigate further.

-jason