CoroutineLiveData randomly throws IllegalArgumentException [140249349]

Fixed

Bug

Status Update

No update yet.

Description

da...@gmail.com

created issue #1

Aug 29, 2019 08:06PM

Component used: lifecycle-livedata-ktx
Version used: 2.2.0-alpha01
Devices/Android versions reproduced on: Android 9

I'm having some random crashes due to CoroutineLiveData
```
Fatal Exception: java.lang.IllegalArgumentException: This source was already added with the different observer
at androidx.lifecycle.MediatorLiveData.addSource + 89(MediatorLiveData.java:89)
at androidx.lifecycle.CoroutineLiveDataKt.addDisposableSource + 102(CoroutineLiveDataKt.java:102)
at androidx.lifecycle.CoroutineLiveData.emitSource$lifecycle_livedata_ktx_release + 200(CoroutineLiveData.java:200)
at androidx.lifecycle.LiveDataScopeImpl$emitSource$2.invokeSuspend + 89(LiveDataScopeImpl.java:89)
at androidx.lifecycle.LiveDataScopeImpl$emitSource$2.invoke(LiveDataScopeImpl.java:11)
at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn + 91(UndispatchedKt.java:91)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext + 156(BuildersKt__Builders_commonKt.java:156)
at kotlinx.coroutines.BuildersKt.withContext + 1(BuildersKt.java:1)
at androidx.lifecycle.LiveDataScopeImpl.emitSource + 88(LiveDataScopeImpl.java:88)
at com.geekorum.ttrss.articles_list.FeedsViewModel$refreshed$1.invokeSuspend + 90(FeedsViewModel.java:90)
at com.geekorum.ttrss.articles_list.FeedsViewModel$refreshed$1.invoke(FeedsViewModel.java:8)
at androidx.lifecycle.BlockRunner$maybeRun$1.invokeSuspend + 147(BlockRunner.java:147)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith + 33(BaseContinuationImpl.java:33)
at kotlinx.coroutines.DispatchedTask.run + 241(DispatchedTask.java:241)
at android.os.Handler.handleCallback + 873(Handler.java:873)
at android.os.Handler.dispatchMessage + 99(Handler.java:99)
at android.os.Looper.loop + 193(Looper.java:193)
at android.app.ActivityThread.main + 6898(ActivityThread.java:6898)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run + 537(RuntimeInit.java:537)
at com.android.internal.os.ZygoteInit.main + 858(ZygoteInit.java:858)
```

From what I understand of CoroutineLiveData source code, when calling `LiveDataScope.emitSource()` the previous source is removed before adding the new one on MediatorLiveData.
```
@MainThread
internal fun emitSource(source: LiveData<T>): DisposableHandle {
clearSource()
val newSource = addDisposableSource(source)
emittedSource = newSource
return newSource
}
```

However the removing is done by launching a new coroutine
```
internal fun <T> MediatorLiveData<T>.addDisposableSource(
source: LiveData<T>
): DisposableHandle {
val disposed = AtomicBoolean(false)
addSource(source) {
if (!disposed.get()) {
value = it
} else {
removeSource(source)
}
}
return object : DisposableHandle {
override fun dispose() {
if (disposed.compareAndSet(false, true)) {
CoroutineScope(Dispatchers.Main).launch {
removeSource(source)
}
}
}
}
}
```

So there is no guarantee that `MediatorLiveData.addSource()` will be called after the removing coroutine is executed. This leads to the IllegalArgumentException in `MediatorLiveData.addSource()`
```
@MainThread
public <S> void addSource(@NonNull LiveData<S> source, @NonNull Observer<? super S> onChanged) {
Source<S> e = new Source<>(source, onChanged);
Source<?> existing = mSources.putIfAbsent(source, e);
if (existing != null && existing.mObserver != onChanged) {
throw new IllegalArgumentException(
"This source was already added with the different observer");
}
if (existing != null) {
return;
}
if (hasActiveObservers()) {
e.plug();
}
}
```

Comments

se...@google.com <se...@google.com> #2Aug 30, 2019 02:17PM

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

commit c60f33e229e31ab328ef6b59dab63b264954831c
Author: Alexandre Elias <aelias@google.com>
Date: Fri Jul 10 16:23:09 2020

Semantics no-op cleanups

Partly in response to lmr's broad code review, I did a pass of
superficial API/implementation cleanup. The main changes are:

- I changed each Boolean SemanticsProperty where false is equivalent to
not being present to take "Unit" instead. This is conceptually
clearer: it avoids questions like "can I cancel out a semantics from a
merged child by setting it to false?" Because "property = Unit" looks
weird, I also changed the style of these to "property()".

- I moved the Semantics id generator closer to where it's used, in
SemanticsModifierCore. I made it internal and an AtomicInt.
(Note that integer ids are heavily used in the Android
AccessibilityNodeInfo APIs so I can't simply remove them entirely.)

- I deleted dead code. Some examples include SemanticsHintOverrides,
a public API not connected to anything, and SemanticsPropertyKey
merge() open method which is never called. (In both cases I have
a different plan in mind for accessibility.)

Fixes: 145951226
Fixes: 145955412
Test: existing tests
Relnote: "Single-value semantics properties now use a calling style.
For example, 'semantics { hidden = true }' is now written as:
'semantics { hidden() }'."

Change-Id: Ic1afd12ea22c926babc9662f1804d80b33aa0cfc

M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/LayoutNodeModifierBenchmark.kt
M ui/ui-core/api/0.1.0-dev15.txt
M ui/ui-core/api/current.txt
M ui/ui-core/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-core/api/public_plus_experimental_current.txt
M ui/ui-core/api/restricted_0.1.0-dev15.txt
M ui/ui-core/api/restricted_current.txt
M ui/ui-core/src/androidAndroidTest/kotlin/androidx/ui/graphics/vector/VectorTest.kt
M ui/ui-core/src/androidAndroidTest/kotlin/androidx/ui/semantics/SemanticsTests.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidActuals.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidComposeView.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidComposeViewAccessibilityDelegateCompat.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidPopup.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/Expect.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsConfiguration.kt
D ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsHintOverrides.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsModifier.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsNode.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsOwner.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsWrapper.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/semantics/SemanticsProperties.kt
M ui/ui-foundation/api/0.1.0-dev15.txt
M ui/ui-foundation/api/current.txt
M ui/ui-foundation/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-foundation/api/public_plus_experimental_current.txt
M ui/ui-foundation/api/restricted_0.1.0-dev15.txt
M ui/ui-foundation/api/restricted_current.txt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Clickable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Dialog.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Scroller.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/selection/Selectable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/selection/Toggleable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/semantics/FoundationSemanticsProperties.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ButtonTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/CardTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/CheckboxScreenshotTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/RadioButtonScreenshotTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ScaffoldTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/SnackbarTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/SurfaceTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ripple/RippleIndicationTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/textfield/TextFieldScreenshotTest.kt
M ui/ui-material/src/main/java/androidx/ui/material/AppBar.kt
M ui/ui-material/src/main/java/androidx/ui/material/TextFieldImpl.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/AssertsTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/CallSemanticsActionTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/ErrorMessagesTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/FindersTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/PrintToStringTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/ScrollToTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/TextActionsTest.kt
M ui/ui-test/src/main/java/androidx/ui/test/Actions.kt
M ui/ui-test/src/main/java/androidx/ui/test/Filters.kt
M ui/ui-text/api/0.1.0-dev15.txt
M ui/ui-text/api/current.txt
M ui/ui-text/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-text/api/public_plus_experimental_current.txt
M ui/ui-text/api/restricted_0.1.0-dev15.txt
M ui/ui-text/api/restricted_current.txt
M ui/ui-text/src/commonMain/kotlin/androidx/ui/text/CoreTextField.kt
M ui/ui-text/src/commonMain/kotlin/androidx/ui/text/TextSemanticsProperties.kt

https://android-review.googlesource.com/1360099

yb...@google.com <yb...@google.com> #3Aug 30, 2019 03:22PM

Reassigned to yb...@google.com.

yea i'll take it.

yb...@google.com <yb...@google.com> #4Aug 30, 2019 06:22PM

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.

yb...@google.com <yb...@google.com> #5Sep 3, 2019 07:33PM

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()
}
}

da...@gmail.com <da...@gmail.com> #6Sep 5, 2019 08:36PM

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)

yb...@google.com <yb...@google.com> #7Sep 6, 2019 12:49AM

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} )
}

ap...@google.com <ap...@google.com> #8Sep 10, 2019 06:53AM

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

yb...@google.com <yb...@google.com> Sep 18, 2019 04:12PM

Marked as fixed.