Calling postponeEnterTransition caused leak [276375110]

Fixed

Bug

Status Update

No update yet.

Description

ni...@ansman.se

created issue #1

Mar 31, 2023 01:25AM

Component used: Fragment
Version used: 1.5.6

If you call Fragment.postponeEnterTransition with a delay, Fragment will post a runnable on a Handler with the specified delay as the delay. This runnable is not removed when calling startPostponedEnterTransition however which means that if the fragment is destroyed it will be retained until the runnable finally runs.

You can easily verify this with LeakCanary by having two fragments where in the first fragment you call postponeEnterTransition(1, TimeUnit.HOURS) and then you navigate to the other fragment. When leak canary runs you can see that the initial fragment is retained.

The solution should be to remove the runnable when calling startPostponedEnterTransition. This might not be feasible in the case where you call postponeEnterTransition before the fragment is attached but it feels OK to ignore that case for now.

Comments

il...@google.com <il...@google.com> Mar 31, 2023 08:55PM

Assigned to jb...@google.com.

ap...@google.com <ap...@google.com> #2Apr 9, 2023 01:42PM

Yigit, do you have time to fix it?

reemission of the same liveData is racy

ni...@ansman.se <ni...@ansman.se> #3Apr 10, 2023 01:59PM

yea i'll take it.

jb...@google.com <jb...@google.com> #4Apr 11, 2023 07:40PM

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.

ni...@hinge.co <ni...@hinge.co> #5Apr 11, 2023 07:41PM

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()
}
}

ap...@google.com <ap...@google.com> #6Apr 12, 2023 04:06PM

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)

jb...@google.com <jb...@google.com> #7Apr 12, 2023 05:04PM

Marked as fixed.

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} )
}

pr...@google.com <pr...@google.com> #8Apr 19, 2023 06:12PM

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