Enum annotations in Kotlin - enums

Question

I have an enumeration that is serialized/deserialized by Gson:
enum class PacketType {
NONE;
[SerializedName("request")]
REQUEST;
[SerializedName("response")]
RESPONSE;
[SerializedName("event")]
EVENT;
}
Unfortunately, I noticed that Gson ignores SerializedName annotations and uses upper case names for enum values. I decided to find out why serialization doesn't work as intended and found out that Kotlin drops all annotations for enum values. How can I make these annotations appear in generated bytecode?

Answer 1

Looks like a bug to me. Please report to the issue tracker.
As a temporary workaround, you can write this class in Java

Answer 2

The issue is now fixed, your code now works fine in Kotlin M9 (0.9.66). If you upgrade to that it'll work as you expect.
e.g.
app build.gradle
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'org.jetbrains.kotlin:kotlin-stdlib:0.9.66'
compile 'com.google.code.gson:gson:2.3'
}
top-level build.gradle
buildscript {
repositories {
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:0.13.2'
classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:0.9.+'
}
}
I confirmed this by making an enum with no relation between the enum names and SerializedName names, and it worked as expected.

Answer 3

If you need to use enum as #Query param in Retrofit you can override toString():
override fun toString(): String {
try {
val annotations = javaClass.getField(name).annotations
for (annotation in annotations) {
if (annotation is SerializedName) {
return annotation.value
}
}
} catch (e: NoSuchFieldException) {
throw RuntimeException(e)
}
return super.toString()
}