Define nested list type using gson while deserializing

Question

By using new AGP v8.0 and full R8 enabled, when I'm trying to deserialize a nested object from a JSON string, the type of nested object is incorrectly identified as LinkedTreeMap by gson.

actions_list.json:

    [
    {
    "name": "actionList1",
    "listA": [
      {
        "name": "action1"
      },
      {
        "name": "action2"
      }
    ] // end of listA
    }, // end of actionList1
    ... // actionList1 to actionListN
    ]

Action class:

    data class Action(
    @SerializedName("name") @Expose val name: String,
    val actions: List<MyAction>,
    var a: Int,
    ...
    var n: Boolean,
    )

MyActions.kt:

    data class MyActions(
    @SerializedName("name")
    val name: String,
    var state: MyActionState?
    )

MyActionState.kt:

    enum class MyActionState{
    Nothing, Running, Done, Failed, Deactivate
    }

proguard-rules.pro:

    -keepattributes Signature, InnerClasses, EnclosingMethod
    -keepattributes RuntimeVisibleAnnotations, RuntimeVisibleParameterAnnotations
    -dontwarn javax.annotation.**
    -dontwarn kotlin.Unit
    -dontwarn retrofit2.KotlinExtensions
    -dontwarn retrofit2.KotlinExtensions$*
    -dontwarn okhttp3.**
    -keep class okhttp3.** { *;}
    -dontwarn okio.**
    -keepattributes SourceFile,LineNumberTable
    -keep class com.google.gson.*
    -keep interface com.google.gson.*
    -keep class * extends com.google.gson.reflect.TypeToken
    -keep public class * implements java.lang.reflect.Type
    -keep class path.to.all.app.class
    -keep interface path.to.all.app.class
    -keep enum path.to.all.app.class
    -keepattributes *Annotation*
    -keepattributes AnnotationDefault
    -keepattributes Signature

and this how i converts json array to List:

    val jsonString: String = this.assets.open("actions/actions_list.json")
    .bufferedReader()
    .use { it.readText() }
    
    val type = TypeToken.getParameterized(List::class.java,Action::class.java).type
    
    return Gson().fromJson(jsonString, type )

When minifyEnabled is true in app build.gradle, List is converted to LinkedTreeMap. I have too many nested object, is there any way that i fix this without Custom Desrializer class, TypeConverters, disable full r8 mode and downgrade gradle version?

Answer 1

Adding these lines to the proguard-rules.pro fixed the problem:

-keepclassmembernames class path.to.MyActions {<fields>;}
-keepclassmembernames class path.to.Action{<fields>;}