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Collect renderings on context specified in WorkflowLayout.take #1424

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Collect renderings on context specified in WorkflowLayout.take #1424

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Collect renderings on context specified in WorkflowLayout.take
steve-the-edwards Oct 8, 2025
e370e97
Apply changes from ktLintFormat
steve-the-edwards Oct 8, 2025
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20 changes: 10 additions & 10 deletions workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/WorkflowLayout.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package com.squareup.workflow1.ui

import android.content.Context
import android.os.Build.VERSION
import android.os.Looper
import android.os.Parcel
import android.os.Parcelable
import android.os.Parcelable.Creator
Expand All @@ -16,10 +17,10 @@ import androidx.lifecycle.coroutineScope
import androidx.lifecycle.repeatOnLifecycle
import com.squareup.workflow1.ui.androidx.OnBackPressedDispatcherOwnerKey
import com.squareup.workflow1.ui.androidx.WorkflowAndroidXSupport.onBackPressedDispatcherOwnerOrNull
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.Job
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import kotlin.coroutines.CoroutineContext
import kotlin.coroutines.EmptyCoroutineContext

Expand Down Expand Up @@ -89,8 +90,8 @@ public class WorkflowLayout(
* @param [repeatOnLifecycle] the lifecycle state in which renderings should be actively
* updated. Defaults to STARTED, which is appropriate for Activity and Fragment.
* @param [collectionContext] additional [CoroutineContext] we want for the coroutine that is
* launched to collect the renderings. This should not override the [CoroutineDispatcher][kotlinx.coroutines.CoroutineDispatcher]
* but may include some other instrumentation elements.
* launched to collect the renderings, can include a different dispatcher - but it should be
* a main thread dispatcher!
*
* @return the [Job] started to collect [renderings], to give callers the option to
* [cancel][Job.cancel] collection -- e.g., before calling [take] again with a new
Expand All @@ -104,16 +105,15 @@ public class WorkflowLayout(
repeatOnLifecycle: State = STARTED,
collectionContext: CoroutineContext = EmptyCoroutineContext
): Job {
// We remove the dispatcher as we want to use what is provided by the lifecycle.coroutineScope.
val contextWithoutDispatcher = collectionContext.minusKey(CoroutineDispatcher.Key)
val lifecycleDispatcher = lifecycle.coroutineScope.coroutineContext[CoroutineDispatcher.Key]
// Just like https://medium.com/androiddevelopers/a-safer-way-to-collect-flows-from-android-uis-23080b1f8bda
return lifecycle.coroutineScope.launch(contextWithoutDispatcher) {
return lifecycle.coroutineScope.launch {
lifecycle.repeatOnLifecycle(repeatOnLifecycle) {
require(coroutineContext[CoroutineDispatcher.Key] == lifecycleDispatcher) {
"Collection dispatch should happen on the lifecycle's dispatcher."
withContext(collectionContext) {
require(Looper.myLooper() == Looper.getMainLooper()) {
"Collection dispatch should happen on the main thread!"
}
renderings.collect { show(it) }
}
renderings.collect { show(it) }
}
}
}
Expand Down
19 changes: 0 additions & 19 deletions workflow-ui/core-android/src/test/java/com/squareup/workflow1/ui/WorkflowLayoutTest.kt
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Expand Up @@ -17,14 +17,12 @@ import com.squareup.workflow1.ui.androidx.OnBackPressedDispatcherOwnerKey
import com.squareup.workflow1.ui.navigation.WrappedScreen
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.flow.flowOf
import kotlinx.coroutines.test.UnconfinedTestDispatcher
import kotlinx.coroutines.test.runTest
import org.junit.Test
import org.junit.runner.RunWith
import org.robolectric.RobolectricTestRunner
import org.robolectric.annotation.Config
import kotlin.coroutines.CoroutineContext

@RunWith(RobolectricTestRunner::class)
// SDK 28 required for the four-arg constructor we use in our custom view classes.
Expand Down Expand Up @@ -92,23 +90,6 @@ internal class WorkflowLayoutTest {
unoriginal.show(BScreen(), env)
}

@Test fun usesLifecycleDispatcher() {
val lifecycleDispatcher = UnconfinedTestDispatcher()
val collectionContext: CoroutineContext = UnconfinedTestDispatcher()
val testLifecycle = TestLifecycleOwner(
Lifecycle.State.RESUMED,
lifecycleDispatcher
)

workflowLayout.take(
lifecycle = testLifecycle.lifecycle,
renderings = flowOf(WrappedScreen(), WrappedScreen()),
collectionContext = collectionContext
)

// No crash then we safely removed the dispatcher.
}

@Test fun takes() {
val lifecycleDispatcher = UnconfinedTestDispatcher()
val testLifecycle = TestLifecycleOwner(
Expand Down
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