[SOLVED] How can I get correct line numbers using retrace after R8 obfuscation?

I am using Android Studio 4.1.3 and its various bundled tools (AGP 4.1.3, Gradle 6.5, Android SDK Build Tools 31-rc2, Platform Tools 31.0.1, SDK Tools 26.1.1). I am using the default R8 tool.

I am obfuscating release builds like this:

release {
   // Enables code shrinking, obfuscation, and optimization for only
   // your project's release build type.
   minifyEnabled true

   // Enables resource shrinking, which is performed by the
   // Android Gradle plugin.
   shrinkResources false

   // Includes the default ProGuard rules files that are packaged with
   // the Android Gradle plugin. To learn more, go to the section about
   // R8 configuration files.
   proguardFiles getDefaultProguardFile(
           'proguard-android.txt'),
           'proguard-rules.pro'
}

My Proguard-rules.pro file has this at the top:

# hide the original source file name.
-renamesourcefileattribute SourceFile

-keepattributes Exceptions,InnerClasses,Signature,Deprecated,SourceFile,LineNumberTable,*Annotation*,EnclosingMethod

After the release build is created, here is an example stack trace - the first line shows that it obfuscated the class name (SplashActivity$a), renamed the source to 'SourceFile', and obfuscated the line number (2):

at com.reddragon.intouch.ui.SplashActivity$a.onStart(SourceFile:2)
at io.reactivex.rxjava3.observers.DisposableObserver.onSubscribe(SourceFile:2)
at io.reactivex.rxjava3.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.onSubscribe(SourceFile:15)
at io.reactivex.rxjava3.internal.operators.observable.ObservableSubscribeOn.subscribeActual(SourceFile:2)
at io.reactivex.rxjava3.core.Observable.subscribe(SourceFile:12)
at io.reactivex.rxjava3.internal.operators.observable.ObservableObserveOn.subscribeActual(SourceFile:4)
at io.reactivex.rxjava3.core.Observable.subscribe(SourceFile:12)
at io.reactivex.rxjava3.core.Observable.subscribeWith(SourceFile:1)
at com.reddragon.intouch.ui.SplashActivity.onCreate(SourceFile:16)
at android.app.Activity.performCreate(Activity.java:7183)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2910)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

Using the retrace.bat tool (located in ~\SDK\tools\proguard\bin) with the appropriate mappings.txt file from the release build against that stack trace results in this output:

at com.reddragon.intouch.ui.SplashActivity$1.void onStart()(SourceFile:2)
at io.reactivex.rxjava3.observers.DisposableObserver.void onSubscribe(io.reactivex.rxjava3.disposables.Disposable)(SourceFile:2)
at io.reactivex.rxjava3.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.void onSubscribe(io.reactivex.rxjava3.disposables.Disposable)(SourceFile:15)
at io.reactivex.rxjava3.internal.operators.observable.ObservableSubscribeOn.void subscribeActual(io.reactivex.rxjava3.core.Observer)(SourceFile:2)
at io.reactivex.rxjava3.core.Observable.void subscribe(io.reactivex.rxjava3.core.Observer)(SourceFile:12)
at io.reactivex.rxjava3.internal.operators.observable.ObservableObserveOn.void subscribeActual(io.reactivex.rxjava3.core.Observer)(SourceFile:4)
at io.reactivex.rxjava3.core.Observable.void subscribe(io.reactivex.rxjava3.core.Observer)(SourceFile:12)
at io.reactivex.rxjava3.core.Observable.io.reactivex.rxjava3.core.Observer subscribeWith(io.reactivex.rxjava3.core.Observer)(SourceFile:1)
at com.reddragon.intouch.ui.SplashActivity.void onCreate(android.os.Bundle)(SourceFile:16)
at android.app.Activity.performCreate(Activity.java:7183)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2910)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

Notice that the class names properly got de-obfuscated (SplashActivity$a became SplashActivity$1), but the line numbers did not get un-obfuscated (it still shows line 2 which is wrong). Interestingly, if I include this section in build.gradle:

debug {
  debuggable true
  minifyEnabled true

  // Enables resource shrinking, which is performed by the
  // Android Gradle plugin.
  shrinkResources false

  // Includes the default ProGuard rules files that are packaged with
  // the Android Gradle plugin. To learn more, go to the section about
  // R8 configuration files.
  proguardFiles getDefaultProguardFile(
          'proguard-android.txt'),
          'proguard-rules.pro'
}

For debug builds, the stack trace output has the file name hidden (it shows as 'SourceFile'), the class name is obfuscated, but the line number is left alone:

at com.reddragon.intouch.ui.SplashActivity$a.onStart(SourceFile:313)
at io.reactivex.rxjava3.observers.DisposableObserver.onSubscribe(SourceFile:74)
at io.reactivex.rxjava3.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.onSubscribe(SourceFile:106)
at io.reactivex.rxjava3.internal.operators.observable.ObservableSubscribeOn.subscribeActual(SourceFile:34)
at io.reactivex.rxjava3.core.Observable.subscribe(SourceFile:13095)
at io.reactivex.rxjava3.internal.operators.observable.ObservableObserveOn.subscribeActual(SourceFile:45)
at io.reactivex.rxjava3.core.Observable.subscribe(SourceFile:13095)
at io.reactivex.rxjava3.core.Observable.subscribeWith(SourceFile:13148)
at com.reddragon.intouch.ui.SplashActivity.onCreate(SourceFile:309)
at android.app.Activity.performCreate(Activity.java:7183)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2910)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

Why can I not get the original line number back after running retrace on the stack trace from the 'release' build? Why is the line number not being obfuscated in the 'debug' build?