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ScopeProvider.coroutineScope throwing behavior when accessin…
…g it before scope is active, or after scope is inactive.
Instead of throwing at call site, we deliver `CoroutineScopeLifecycleException(message: String, cause: OutsideScopeException)` to the `CoroutineExceptionHandler` installed at `RibCoroutinesConfig.exceptionHandler`. Note `cause` is always non-null, and it's either `LifecycleNotStartedException` or `LifecycleEndedException`.
## Motivation
Suppose you have an interactor that starts subscribing to an Rx stream asynchronously.
```kotlin
class MyInteractor {
override fun didBecomeActive() {
runLater {
someObservable.autoDispose(this).subscribe()
}
}
}
```
It is possible that this Rx subscription will be triggered after interactor's already inactive. In that case, subscription will be No-Op.
This is not good code for a major reason: `Interactor` is attempting to do work after it's inactive. In other words, `runLater` does not respect the interactor lifecycle. Still, considering this is some legacy code being migrated from Rx to Coroutines, the new code would look like the following.
```kotlin
class MyInteractor {
override fun didBecomeActive() {
runLater {
someObservable.autoDispose(coroutineScope).subscribe()
}
}
}
```
Unlike the Rx counterpart, this code will sometimes fatally throw. If `ScopeProvider.coroutineScope` is called after the scope's inactive, it will throw `LifecycleEndedException` at call site.
Calling `coroutineScope` outside of lifecycle bounds is always erroneous code. But in order to favour a smoother migration to Coroutines, and to avoid surprises of `val` throwing exceptions, we are changing current implementation to deliver the exception to the `CoroutineExceptionHandler` instead of throwing at call site.
If some app decides to override the default behavior of crashing (in JVM/Android) in face of this erroneous code, one can customize `RibCoroutinesConfig.exceptionHandler` at app startup:
```kotlin
RibCoroutinesConfig.exceptionHandler = CoroutineExceptionHandler { _, throwable ->
when (throwable) {
is CoroutineScopeLifecycleException -> log(throwable) // only log, don't re-throw.
else -> throw throwable
}
}
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39 changes: 39 additions & 0 deletions
39
...d/libraries/rib-coroutines/src/main/kotlin/com/uber/rib/core/internal/DirectDispatcher.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| /* | ||
| * Copyright (C) 2024. Uber Technologies | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.uber.rib.core.internal | ||
|
|
||
| import kotlin.coroutines.CoroutineContext | ||
| import kotlinx.coroutines.CoroutineDispatcher | ||
| import kotlinx.coroutines.Runnable | ||
|
|
||
| /** | ||
| * A coroutine dispatcher that is not confined to any specific thread. It executes the initial | ||
| * continuation of a coroutine in the current call-frame and lets the coroutine resume in whatever | ||
| * thread that is used by the corresponding suspending function, without mandating any specific | ||
| * threading policy. | ||
| * | ||
| * This dispatcher is similar to [Unconfined][com.uber.rib.core.RibDispatchers.Unconfined], with the | ||
| * difference that it does not form an event-loop on nested coroutines, which implies that it has | ||
| * predictable ordering of events with the tradeoff of a risk StackOverflowError. | ||
| * | ||
| * **This is internal API, not supposed to be used by library consumers.** | ||
| */ | ||
| @CoroutinesFriendModuleApi | ||
| public object DirectDispatcher : CoroutineDispatcher() { | ||
| override fun dispatch(context: CoroutineContext, block: Runnable) { | ||
| block.run() | ||
| } | ||
| } |
124 changes: 124 additions & 0 deletions
124
android/libraries/rib-coroutines/src/test/kotlin/com/uber/rib/core/RibCoroutineScopesTest.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| /* | ||
| * Copyright (C) 2024. Uber Technologies | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.uber.rib.core | ||
|
|
||
| import com.google.common.truth.Truth.assertThat | ||
| import com.uber.autodispose.lifecycle.LifecycleEndedException | ||
| import com.uber.autodispose.lifecycle.LifecycleNotStartedException | ||
| import kotlin.contracts.ExperimentalContracts | ||
| import kotlin.contracts.InvocationKind | ||
| import kotlin.contracts.contract | ||
| import kotlinx.coroutines.CoroutineExceptionHandler | ||
| import kotlinx.coroutines.ExperimentalCoroutinesApi | ||
| import kotlinx.coroutines.Job | ||
| import kotlinx.coroutines.awaitCancellation | ||
| import kotlinx.coroutines.isActive | ||
| import kotlinx.coroutines.launch | ||
| import kotlinx.coroutines.test.runCurrent | ||
| import kotlinx.coroutines.test.runTest | ||
| import org.hamcrest.CoreMatchers.instanceOf | ||
| import org.junit.Before | ||
| import org.junit.Rule | ||
| import org.junit.Test | ||
| import org.junit.rules.ExpectedException | ||
| import org.junit.runner.RunWith | ||
| import org.junit.runners.Parameterized | ||
| import org.mockito.kotlin.mock | ||
|
|
||
| @OptIn(ExperimentalCoroutinesApi::class) | ||
| @RunWith(Parameterized::class) | ||
| class RibCoroutineScopesTest( | ||
| private val throwWhenBeforeActive: Boolean, | ||
| private val throwWhenAfterInactive: Boolean, | ||
| ) { | ||
| @get:Rule val ribCoroutinesRule = RibCoroutinesRule() | ||
|
|
||
| @get:Rule val exceptionRule: ExpectedException = ExpectedException.none() | ||
|
|
||
| private val interactor = TestInteractor() | ||
|
|
||
| @Before | ||
| fun setUp() { | ||
| RibCoroutinesConfig.exceptionHandler = CoroutineExceptionHandler { _, throwable -> | ||
| when (throwable) { | ||
| is CoroutineScopeLifecycleException -> if (shouldThrow(throwable)) throw throwable | ||
| else -> throw throwable | ||
| } | ||
| } | ||
| } | ||
|
|
||
| @Test | ||
| fun coroutineScope_whenCalledBeforeActive_throwsCoroutineScopeLifecycleException() = runTest { | ||
| if (throwWhenBeforeActive) { | ||
| exceptionRule.expect(CoroutineScopeLifecycleException::class.java) | ||
| exceptionRule.expectCause(instanceOf(LifecycleNotStartedException::class.java)) | ||
| } | ||
| assertThat(interactor.coroutineScope.isActive).isFalse() | ||
| } | ||
|
|
||
| @Test | ||
| fun coroutineScope_whenCalledAfterInactive_throwsCoroutineScopeLifecycleException() = runTest { | ||
| if (throwWhenAfterInactive) { | ||
| exceptionRule.expect(CoroutineScopeLifecycleException::class.java) | ||
| exceptionRule.expectCause(instanceOf(LifecycleEndedException::class.java)) | ||
| } | ||
| interactor.attachAndDetach {} | ||
| assertThat(interactor.coroutineScope.isActive).isFalse() | ||
| } | ||
|
|
||
| @Test | ||
| fun coroutineScope_whenCalledWhileActive_cancelsWhenInactive() = runTest { | ||
| var launched = false | ||
| val job: Job | ||
| interactor.attachAndDetach { | ||
| job = | ||
| coroutineScope.launch { | ||
| launched = true | ||
| awaitCancellation() | ||
| } | ||
| runCurrent() | ||
| assertThat(launched).isTrue() | ||
| assertThat(job.isActive).isTrue() | ||
| } | ||
| assertThat(job.isCancelled).isTrue() | ||
| } | ||
|
|
||
| private fun shouldThrow(e: CoroutineScopeLifecycleException): Boolean = | ||
| (throwWhenBeforeActive && e.cause is LifecycleNotStartedException) || | ||
| (throwWhenAfterInactive && e.cause is LifecycleEndedException) | ||
|
|
||
| companion object { | ||
| @JvmStatic | ||
| @Parameterized.Parameters(name = "throwWhenBeforeActive = {0}, throwWhenAfterInactive = {1}") | ||
| fun data() = | ||
| listOf( | ||
| arrayOf(true, true), | ||
| arrayOf(true, false), | ||
| arrayOf(false, true), | ||
| arrayOf(false, false), | ||
| ) | ||
| } | ||
| } | ||
|
|
||
| private class TestInteractor : Interactor<Unit, Router<*>>() | ||
|
|
||
| @OptIn(ExperimentalContracts::class) | ||
| private inline fun TestInteractor.attachAndDetach(block: TestInteractor.() -> Unit) { | ||
| contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) } | ||
| InteractorHelper.attach(this, Unit, mock(), null) | ||
| block() | ||
| InteractorHelper.detach(this) | ||
| } |