Connection Status does not work correctly when in android release mode

[GabrielCoffee9]

Is this a how to question?
No

Is this a native Spotify SDK issue?
No

Have you searched for existing issues?
Yes

Are you using a Free or Premium Spotify account?
Premium

Are you aware of the limitations of Free Spotify accounts?
Yes

Expected behavior
Connection Status subscription works in android release mode

Describe the bug
SpotifySdk.subscribeConnectionStatus() doesn't work when compiled in release mode on android.

Steps to Reproduce
Steps to reproduce the behavior:

1. Create a new Flutter application with Android platform
2. Add Spotify_sdk package -> flutter pub add spotify_sdk
3. Run auto setup for android -> dart run spotify_sdk:android_setup
4. Run -> flutter build apk
5. Try to listen the function SpotifySdk.subscribeConnectionStatus()
6. Use the function SpotifySdk.connectToSpotifyRemote() to sign in
7. Nothing happens (The connection status event is not working).

Spotify_sdk Flutter package version 3.0.2

Flutter version 3.24.3

spotify_sdk:
    dependency: "direct main"
    description:
      name: spotify_sdk
      sha256: "4c7a3b79f0370e7ae8ac07cad5e630d0bb3ad118f4c16219ec37f6988a65465e"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.2"

Target Platform, Version & Device

• OS & Version: Tested Android 14 and 15
• Device: Tested in Android Emulator Medium Phone API 34 and 35

Development OS

• Windows

That bug only happens in release mode (on Android), where the Connection Status does not work correctly due to probably a parsing problem.

Found out that:

In the function ConnectionStatus _$ConnectionStatusFromJson(Map<String, dynamic> json) in the file:

"C:\Users{USERNAME}\AppData\Local\Pub\Cache\hosted\pub.dev\spotify_sdk-3.0.2\lib\models\connection_status.g.dart"

The parameter json is filled with keys:'a', 'b', 'c' and 'd' when in release mode, instead of 'connected', 'message', 'errorCode' and 'errorDetails'. The values are ok but the json keys are wrong.

As a temporary workaround I modified two files:

First, I added this import at the very top of the file: C:\Users\{USERNAME}\AppData\Local\Pub\Cache\hosted\pub.dev\spotify_sdk-3.0.2\lib\models\connection_status.dart

import 'package:flutter/foundation.dart';

Second, I modified this function on the file: C:\Users\{USERNAME}\AppData\Local\Pub\Cache\hosted\pub.dev\spotify_sdk-3.0.2\lib\models\connection_status.g.dart

ConnectionStatus _$ConnectionStatusFromJson(Map<String, dynamic> json) {
  if (kReleaseMode) {
    return ConnectionStatus(
      json['b'] as String?,
      json['c'] as String?,
      json['d'] as String?,
      connected: json['a'] as bool,
    );
  } else {
    return ConnectionStatus(
      json['message'] as String?,
      json['errorCode'] as String?,
      json['errorDetails'] as String?,
      connected: json['connected'] as bool,
    );
  }
}

After the changes ConnectionStatus seems to work properly.

[tophattom]

I managed to work around this issue without modifying the cached Dart files.

I added the following Proguard rules to android/app/proguard-rules.pro. The first six lines were copied from a missing-rules.txt file generated when trying to build the app in release mode. The GSON specific config was copied from their example here https://github.com/google/gson/blob/main/examples/android-proguard-example/proguard.cfg.

-dontwarn com.fasterxml.jackson.databind.deser.std.StdDeserializer
-dontwarn com.fasterxml.jackson.databind.ser.std.StdSerializer
-dontwarn com.google.errorprone.annotations.FormatMethod
-dontwarn com.spotify.base.annotations.NotNull
-dontwarn javax.annotation.Nonnull
-dontwarn javax.annotation.Nullable

##---------------Begin: proguard configuration for Gson  ----------
# Gson uses generic type information stored in a class file when working with fields. Proguard
# removes such information by default, so configure it to keep all of it.
-keepattributes Signature

# For using GSON @Expose annotation
-keepattributes *Annotation*

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

# Application classes that will be serialized/deserialized over Gson
-keep class com.google.gson.examples.android.model.** { <fields>; }

# Prevent proguard from stripping interface information from TypeAdapter, TypeAdapterFactory,
# JsonSerializer, JsonDeserializer instances (so they can be used in @JsonAdapter)
-keep class * extends com.google.gson.TypeAdapter
-keep class * implements com.google.gson.TypeAdapterFactory
-keep class * implements com.google.gson.JsonSerializer
-keep class * implements com.google.gson.JsonDeserializer

# Prevent R8 from leaving Data object members always null
-keepclassmembers,allowobfuscation class * {
  @com.google.gson.annotations.SerializedName <fields>;
}

# 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

##---------------End: proguard configuration for Gson  ----------

I suspect there might be a way to include these in the spotify-app-remote module and have them generated by the setup script but I'm not at all familiar enough with Gradle etc. to figure that out.

Hope this helps!

[AndreaCavallo98]

@tophattom thank you so much, I have been stuck for a day because I wasn't understanding why the subscribePlayerState wasn't working on the apk but in the emulator yes. Since I'm not that skilled If by any chance you can explain a bit more in detail what was the reason why it wasn't working it would be really helpful.

[tophattom]

@AndreaCavallo98 When building a release version, the code is minified and mangled to save space and to make it harder to disassemble using a tool called R8 (I believe). This means, for example, that variable names are changed to be as short as possible. GSON automatically generates a JSON string from a class instance using the variable names as the keys in the JSON object. So, when the variables are shortened, the generated JSON will contain wrong keys.

The Proguard configuration tells the minifier what parts of the code it should and shouldn't touch. The part from the GSON repository tells the minifier to leave parts relevant to the JSON generation as-is.

Like I said, I'm not really familiar with the Android stuff so this explanation is probably somewhat wrong on the details. But the basic principle should apply.