RegistrationIntentService leaks a closeable FileOutputStream

[troy-lamerton]

[REQUIRED] Please fill in the following fields:

• Pre-built SDK from the website or open-source from this repo: prebuilt
• Firebase C++ SDK version: 8.11.0
• Problematic Firebase Component: Messaging
• Other Firebase Components in use: none
• Platform you are using the C++ SDK on: Mac
• Platform you are targeting: Android

[REQUIRED] Please describe the issue here:

• enable strict mode
• shows that closeable is leaked here https://github.com/firebase/firebase-cpp-sdk/blob/v9.0.0/messaging/src/android/java/com/google/firebase/messaging/cpp/RegistrationIntentService.java#L63

2022-05-26 10:43:36.813 9571-9584/? D/StrictMode: StrictMode policy violation: android.os.strictmode.LeakedClosableViolation: A resource was acquired at attached stack trace but never released. See java.io.Closeable for information on avoiding resource leaks.
        at android.os.StrictMode$AndroidCloseGuardReporter.report(StrictMode.java:1877)
        at dalvik.system.CloseGuard.warnIfOpen(CloseGuard.java:286)
        at sun.nio.ch.FileChannelImpl.finalize(FileChannelImpl.java:175)
        at java.lang.Daemons$FinalizerDaemon.doFinalize(Daemons.java:289)
        at java.lang.Daemons$FinalizerDaemon.runInternal(Daemons.java:276)
        at java.lang.Daemons$Daemon.run(Daemons.java:137)
        at java.lang.Thread.run(Thread.java:919)
     Caused by: java.lang.Throwable: Explicit termination method 'close' not called
        at dalvik.system.CloseGuard.open(CloseGuard.java:237)
        at sun.nio.ch.FileChannelImpl.<init>(FileChannelImpl.java:110)
        at sun.nio.ch.FileChannelImpl.open(FileChannelImpl.java:128)
        at java.io.FileOutputStream.getChannel(FileOutputStream.java:469)
        at com.google.firebase.messaging.cpp.RegistrationIntentService.writeTokenToInternalStorage(SourceFile:6)
        at com.google.firebase.messaging.cpp.RegistrationIntentService.onHandleIntent(SourceFile:3)
        at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:78)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:237)
        at android.os.HandlerThread.run(HandlerThread.java:67)

Steps to reproduce:

• Android project using Firebase Messaging
• enable strict mode

StrictMode.setVmPolicy(StrictMode.VmPolicy.Builder()
                    .detectActivityLeaks()
                    .detectLeakedClosableObjects()
                    .penaltyLog()
                    .build())

• check logcat for D/StrictMode logs

100% reproduce.

Sample project that reproduces the bug:

• Use https://github.com/firebase/quickstart-android/tree/master/messaging
• go to file https://github.com/firebase/quickstart-android/blob/master/messaging/app/src/main/java/com/google/firebase/quickstart/fcm/EntryChoiceActivity.kt
• add code:

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        StrictMode.setVmPolicy(
            StrictMode.VmPolicy.Builder()
                .detectLeakedClosableObjects()
                .penaltyLog()
                .build()
        )
    }

[chkuang-g]

@troy-lamerton

This looks legit. Thank you for reporting. Let me see if I can put together a quick fix for this.