Using proguard with GSON and RoboGuice fails when using a EnumTypeAdapter

Question

When trying to use a EnumTypeAdapter with Proguard, it results in a AssertionError in Gson.getAdapter(). This error seems to be due to type information being lost... below is all the relevant source code:

The Exception:

03-18 13:27:12.905: ERROR/roboguice(12139): Throwable caught during background processing
    java.lang.AssertionError
    at com.google.gson.internal.bind.TypeAdapters$EnumTypeAdapter.<init>(Unknown Source)
    at com.google.gson.internal.bind.TypeAdapters$24.create(Unknown Source)
    at com.google.gson.Gson.getAdapter(Unknown Source)

The EnumTypeAdapter being used:

public class OperationResultSerializer implements JsonDeserializer<OperationResult>, JsonSerializer<OperationResult> {

@Override
public OperationResult deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
    int value = json.getAsJsonPrimitive().getAsInt();
    return OperationResult.values()[value];
}

@Override
public JsonElement serialize(OperationResult src, Type typeOfSrc, JsonSerializationContext context) {
    return new JsonPrimitive(src.ordinal());
}
}

How I am constructing my GSON object:

            gson = new GsonBuilder()
                .registerTypeAdapter(Calendar.class, new WcfCalendarSerializer())
                .registerTypeAdapter(OperationResult.class, new OperationResultSerializer())
                .registerTypeAdapter(FieldName.class, new FieldNameSerializer())
                .registerTypeAdapter(MealType.class, new MealTypeSerializer())
                .create();

My ProGuard Config:

#-dontusemixedcaseclassnames: Necessary when building on windows where x.class and X.class is the same file
-dontusemixedcaseclassnames

-keepattributes *Annotation*
-keepattributes Signature

# Preserve the special static methods that are required in all enumeration classes.
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep public class * extends android.app.Application
-keep public class * extends android.app.Activity
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep class * extends android.view.View { 
  public <init>(android.content.Context); 
  public <init>(android.content.Context, android.util.AttributeSet); 
  public <init>(android.content.Context, android.util.AttributeSet, int); 
  public void set*(...); 
}
-keep class com.google.inject.** { *; } 
-keep class javax.inject.** { *; } 
-keep class javax.annotation.** { *; } 
-keep class roboguice.** { *; } 

-keep class * extends android.preference.Preference { 
  public <init>(android.content.Context); 
  public <init>(android.content.Context, android.util.AttributeSet); 
  public <init>(android.content.Context, android.util.AttributeSet, int); 
  public void set*(...); 
}   

# Gson specific classes
-keep class sun.misc.Unsafe { *; }
#-keep class com.google.gson.stream.** { *; }

###Action bar sherlock 
-keep class android.support.v4.app.** { *; } 
-keep interface android.support.v4.app.** { *; } 
-keep class com.actionbarsherlock.** { *; } 
-keep interface com.actionbarsherlock.** { *; } 

###RoboGuice 
-keepclassmembers class * { 
    @com.google.inject.Inject <init>(...); 
} 
-keepclassmembers class * { 
    void *(**On*Event); 
} 
-keep public class roboguice.** 
-keep class com.google.inject.** 
-keep class com.google.gson.** {*;}

#datacontract
-keep public class com.ordering.datacontract.*
-keepclassmembers class com.ordering.datacontract.*

# LVL License binder class
-keep class com.android.vending.licensing.ILicensingService    


-dontwarn
-ignorewarnings

As stated earlier, I suspect something is failing due to type information being lost - after digging into the GSON source code, this is the code that is called to resolve the EnumTypeAdapter... clearly the getEnumConstants is returning a Name that does not exist as a field of the type classOfT. But I am unsure how that is possible.

private static final class EnumTypeAdapter<T extends Enum<T>> extends TypeAdapter<T> {
private final Map<String, T> nameToConstant = new HashMap<String, T>();
private final Map<T, String> constantToName = new HashMap<T, String>();

public EnumTypeAdapter(Class<T> classOfT) {
  try {
    for (T constant : classOfT.getEnumConstants()) {
      String name = constant.name();
      SerializedName annotation = classOfT.getField(name).getAnnotation(SerializedName.class);
      if (annotation != null) {
        name = annotation.value();
      }
      nameToConstant.put(name, constant);
      constantToName.put(constant, name);
    }
  } catch (NoSuchFieldException e) {
    throw new AssertionError();
  }
}
public T read(JsonReader in) throws IOException {
  if (in.peek() == JsonToken.NULL) {
    in.nextNull();
    return null;
  }
  return nameToConstant.get(in.nextString());
}

public void write(JsonWriter out, T value) throws IOException {
  out.value(value == null ? null : constantToName.get(value));
}
  }

I have searched all over for possible solutions but have not found much help. Maybe someone has run into this before and can point me in the right direction?

Answer 1

I went through and examined the resulting APK decompiled. I believe the problem is related to some enum type losing its members during obfuscation.

Be sure to keep enum class members:

-keepclassmembers enum * {
 public static **[] values();
 public static ** valueOf(java.lang.String);
 }

Also - make sure ALL of the classes being used in GSON are being retained:

 -keep public class com.company.ordering.datacontract.** {
 public protected *;
 }

 -keep public class com.company.ordering.service.request.** {
 public protected *;
 }
 -keep public class com.company.ordering.service.response.** {
 public protected *;
 }

See full config @ pastebin.com/r5Jg3yY2