IssueTracker

Yigit, do you have time to fix it?

reemission of the same liveData is racy

yea i'll take it.

Thanks for the detailed analysis. This may not be an issue anymore since we've started using Main.immediate there but I' not sure; I'll try to create a test case.

just emitting same live data reproduces the issue.

    @Test
    fun raceTest() {
        val subLiveData = MutableLiveData(1)
        val subject = liveData(testScope.coroutineContext) {
            emitSource(subLiveData)
            emitSource(subLiveData) //crashes
        }
        subject.addObserver().apply {
            testScope.advanceUntilIdle()
        }
    }

With 2.2.0-alpha04 (that use Main.immediate), the issue seems to be still there (I tested it by calling emitSource() twice, like your test case)

yea sorry immediate does not fix it.
I actually have a WIP fix for it:
https://android-review.googlesource.com/c/platform/frameworks/support/+/1112186

if your case is the one i found (emitting same LiveData multiple times, as shown in #5) you can work around it by adding a dummy transformation.


val subLiveData = MutableLiveData(1)
        val subject = liveData(testScope.coroutineContext) {
            emitSource(subLiveData.map {it })
            emitSource(subLiveData.map {it} )
        }

Project: platform/frameworks/support
Branch: androidx-master-dev

commit af12e75e6b4110f48e44ca121466943909de8f06
Author: Yigit Boyar <yboyar@google.com>
Date:   Tue Sep 03 12:58:11 2019

    Fix coroutine livedata race condition
   
    This CL fixes a bug in liveData builder where emitting same
    LiveData source twice would make it crash because the second
    emission registry could possibly happen before first one is
    removed as source.
   
    We fix it by using a suspending dispose function. It does feel
    a bit hacky but we cannot make DisposableHandle.dispose async
    and we do not want to block there. This does not mean that there
    is a problem if developer disposes it manually since our emit
    functions take care of making sure it disposes (and there is
    no other way to add source to the underlying MediatorLiveData)
   
    Bug: 140249349
    Test: BuildLiveDataTest#raceTest_*
   
    Change-Id: I0b464c242a583da4669af195cf2504e2adc4de40

M       lifecycle/lifecycle-livedata-ktx/api/2.2.0-alpha05.txt
M       lifecycle/lifecycle-livedata-ktx/api/current.txt
M       lifecycle/lifecycle-livedata-ktx/api/public_plus_experimental_2.2.0-alpha05.txt
M       lifecycle/lifecycle-livedata-ktx/api/public_plus_experimental_current.txt
M       lifecycle/lifecycle-livedata-ktx/api/restricted_2.2.0-alpha05.txt
M       lifecycle/lifecycle-livedata-ktx/api/restricted_current.txt
M       lifecycle/lifecycle-livedata-ktx/src/main/java/androidx/lifecycle/CoroutineLiveData.kt
M       lifecycle/lifecycle-livedata-ktx/src/test/java/androidx/lifecycle/BuildLiveDataTest.kt

https://android-review.googlesource.com/1112186
https://goto.google.com/android-sha1/af12e75e6b4110f48e44ca121466943909de8f06

Any plans on fixing it in nearest feature without workarounds?

P.S. Why it wasn't possible to fix the issue before releasing stable?
Adding @Keep manually sounds like it is 2015 now developers should struggle with their own set of rules for every single components.

Project: platform/frameworks/base
Branch: master

commit 4bdc698d9f8fb4f85464d554cabeb954104ec0a3
Author: Jeremy Woods <jbwoods@google.com>
Date:   Fri Feb 28 19:42:38 2020

    Generate "keep" rules for android:name and class attributes
   
    We should keep classes that are in the android:name or class xml
    attributes.
   
    Test: m -j aapt2_tests
    Bug: 142601969
    Change-Id: Ia67365bd702bae75d38b9572d68e9930e856e0f8

M       tools/aapt2/java/ProguardRules.cpp
M       tools/aapt2/java/ProguardRules_test.cpp

https://android-review.googlesource.com/1247267

AGP will not back port these since it's too late in the release process for them. However, you can force older AGP to use the newer aapt2.
You can do it in two ways, with the first approach being much safer:
1) In your build.gradle force gradle to use the newer version:
configurations.matching { it.name == '_internal_aapt2_binary' }.all { config ->
        config.resolutionStrategy.eachDependency { details ->
            details.useVersion("4.1.0-alpha04-6296993")
        }
    }

2) If for some reason the above doesn't work, you can manually download the gmaven jar file for "com.android.tools.build:aapt2:4.1.0-alpha04-6296993" (https://dl.google.com/dl/android/maven2/com/android/tools/build/aapt2/4.1.0-alpha04-6296993/aapt2-4.1.0-alpha04-6296993-[windows/darwin/linux].jar - choose the right platform), unpack somewhere and use android.aapt2FromMavenOverride to set the path to the aapt2 executable you want to use. Be careful to use the right platform.

Note: check the version when it comes out, most likely it should match this but it's possible we update the prebuilts again before then. 4.1 canary 4 is not out yet, so this will only be available in gmaven once that canary is released.

Follow pre-release version updates here: https://androidstudio.googleblog.com/

Gracias