Caused by java.lang.RuntimeException: Missing type parameter

Question

I'm retrieving a json and when I convert it to List using gson, the app crashes. The proguard is on and the problem is there.

fun getQuestions(): List<Question>? {
    val json = getQuestionsJsonData()
    return GsonBuilder().create().fromJson(
        json,
        object : TypeToken<List<Question>?>() {}.type
    )
}

As I've obfuscated my code, I'm not able to see crash log in logcat, so I send it to firebase crashlitycs. The error message is - Caused by java.lang.RuntimeException: Missing type parameter.

Maybe the Question type get's obfuscated or something similar happens. My proguard file:

-keepclassmembers,allowobfuscation class * {
  @com.google.gson.annotations.SerializedName <fields>;
}

-keepclassmembers class **.R$* {
    public static <fields>;
}

#Serialized
-keepnames class * implements java.io.Serializable
-keepclassmembers class * implements java.io.Serializable {
    static final long serialVersionUID;
    private static final java.io.ObjectStreamField[] serialPersistentFields;
    !static !transient <fields>;
    !private <fields>;
    !private <methods>;
    private void writeObject(java.io.ObjectOutputStream);
    private void readObject(java.io.ObjectInputStream);
    java.lang.Object writeReplace();
    java.lang.Object readResolve();
}

# Uncomment this to preserve the line number information for
# debugging stack traces.
-keepattributes SourceFile,LineNumberTable

# If you keep the line number information, uncomment this to
# hide the original source file name.
-renamesourcefileattribute SourceFile

Maybe I have to add something in proguard file?

P.S. The problem is only on Gradle 7.1.0

Answer 1

In my case was just adding the following to proguard configuration:

# Retain generic signatures of TypeToken and its subclasses with R8 version 3.0 and higher.
-keep,allowobfuscation,allowshrinking class com.google.gson.reflect.TypeToken
-keep,allowobfuscation,allowshrinking class * extends com.google.gson.reflect.TypeToken

Here you go the full set of options that are needed for Gson -> https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg

Answer 2

Well, after changing my TypeToken code, seems it's working.

Non working code:

return GsonBuilder().create().fromJson(
    json,
    object : TypeToken<List<Question>?>() {}.type
)

Working solution:

return GsonBuilder().create().fromJson(
    json,
    TypeToken.getParameterized(List::class.java, Question::class.java).type
)