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Fix potential for deadlocks in Worker binding. #582

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merged 1 commit into from
May 12, 2023
Merged

Fix potential for deadlocks in Worker binding. #582

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19 changes: 5 additions & 14 deletions android/libraries/rib-base/src/main/kotlin/com/uber/rib/core/FlowAsScope.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -17,25 +17,16 @@

package com.uber.rib.core

import com.uber.autodispose.ScopeProvider
import com.uber.autodispose.lifecycle.LifecycleEndedException
import com.uber.autodispose.lifecycle.LifecycleNotStartedException
import io.reactivex.CompletableSource
import kotlin.coroutines.CoroutineContext
import kotlin.coroutines.EmptyCoroutineContext
import kotlinx.coroutines.flow.SharedFlow
import kotlinx.coroutines.flow.first
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.takeWhile
import kotlinx.coroutines.rx2.rxCompletable

/**
* Converts a [SharedFlow] of lifecycle events into a [ScopeProvider]. See [asScopeCompletable] for
* constraints.
*/
internal fun <T : Comparable<T>> SharedFlow<T>.asScopeProvider(
range: ClosedRange<T>,
context: CoroutineContext = EmptyCoroutineContext,
): ScopeProvider = asScopeCompletable(range, context).asScopeProvider()

/**
* Converts a [SharedFlow] of lifecycle events into a [CompletableSource] that completes once the
* flow emits the ending event.
Expand All @@ -50,7 +41,9 @@ internal fun <T : Comparable<T>> SharedFlow<T>.asScopeCompletable(
context: CoroutineContext = EmptyCoroutineContext,
): CompletableSource {
ensureAlive(range)
return rxCompletable(RibDispatchers.Unconfined + context) { first { it == range.endInclusive } }
return rxCompletable(RibDispatchers.Unconfined + context) {
takeWhile { it < range.endInclusive }.collect()
}
}

private fun <T : Comparable<T>> SharedFlow<T>.ensureAlive(range: ClosedRange<T>) {
Expand All @@ -60,5 +53,3 @@ private fun <T : Comparable<T>> SharedFlow<T>.ensureAlive(range: ClosedRange<T>)
lastEmitted >= range.endInclusive -> throw LifecycleEndedException()
}
}

private fun CompletableSource.asScopeProvider() = ScopeProvider { this }
8 changes: 7 additions & 1 deletion android/libraries/rib-base/src/main/kotlin/com/uber/rib/core/WorkerBinder.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,13 @@
package com.uber.rib.core

import androidx.annotation.VisibleForTesting
import com.uber.autodispose.ScopeProvider
import com.uber.autodispose.lifecycle.LifecycleScopeProvider
import com.uber.rib.core.lifecycle.InteractorEvent
import com.uber.rib.core.lifecycle.PresenterEvent
import com.uber.rib.core.lifecycle.WorkerEvent
import io.reactivex.Observable
import io.reactivex.subjects.CompletableSubject
import java.lang.ref.WeakReference
import kotlin.coroutines.CoroutineContext
import kotlin.coroutines.EmptyCoroutineContext
Expand Down Expand Up @@ -311,6 +313,10 @@ private fun <T : Comparable<T>> Worker.bind(
CoroutineStart.DEFAULT
}

val completable = CompletableSubject.create()
val scopeProvider = ScopeProvider { completable }
val workerScopeProvider = WorkerScopeProvider(scopeProvider)

/*
* We need `Dispatchers.Unconfined` to react immediately to lifecycle flow emissions, and we need
* `CoroutineStart.Undispatched` to prevent coroutines launched in `onStart` with `Dispatchers.Unconfined`
Expand All @@ -327,6 +333,7 @@ private fun <T : Comparable<T>> Worker.bind(
lifecycle
.takeWhile { it < lifecycleRange.endInclusive }
.onCompletion {
completable.onComplete()
bindAndReportWorkerInfo(
workerDurationListenerWeakRef,
WorkerEvent.STOP,
Expand All @@ -341,7 +348,6 @@ private fun <T : Comparable<T>> Worker.bind(
WorkerEvent.START,
coroutineContext,
) {
val workerScopeProvider = WorkerScopeProvider(lifecycle.asScopeProvider(lifecycleRange))
onStart(workerScopeProvider)
}
}
Expand Down
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