Added API to discard saved state on Android

decompose/api/android/decompose.api

@@ -54,8 +54,10 @@ public final class com/arkivanov/decompose/DefaultComponentContext : com/arkivan
 public final class com/arkivanov/decompose/DefaultComponentContextBuilderKt {
  public static final fun DefaultComponentContext (Landroidx/lifecycle/Lifecycle;Landroidx/savedstate/SavedStateRegistry;Landroidx/lifecycle/ViewModelStore;Landroidx/activity/OnBackPressedDispatcher;)Lcom/arkivanov/decompose/DefaultComponentContext;
  public static synthetic fun DefaultComponentContext$default (Landroidx/lifecycle/Lifecycle;Landroidx/savedstate/SavedStateRegistry;Landroidx/lifecycle/ViewModelStore;Landroidx/activity/OnBackPressedDispatcher;ILjava/lang/Object;)Lcom/arkivanov/decompose/DefaultComponentContext;
- public static final fun defaultComponentContext (Landroidx/fragment/app/Fragment;Landroidx/activity/OnBackPressedDispatcher;)Lcom/arkivanov/decompose/DefaultComponentContext;
- public static final fun defaultComponentContext (Landroidx/savedstate/SavedStateRegistryOwner;)Lcom/arkivanov/decompose/DefaultComponentContext;
+ public static final fun defaultComponentContext (Landroidx/fragment/app/Fragment;Landroidx/activity/OnBackPressedDispatcher;ZLkotlin/jvm/functions/Function0;)Lcom/arkivanov/decompose/DefaultComponentContext;
+ public static final fun defaultComponentContext (Landroidx/savedstate/SavedStateRegistryOwner;ZLkotlin/jvm/functions/Function0;)Lcom/arkivanov/decompose/DefaultComponentContext;
+ public static synthetic fun defaultComponentContext$default (Landroidx/fragment/app/Fragment;Landroidx/activity/OnBackPressedDispatcher;ZLkotlin/jvm/functions/Function0;ILjava/lang/Object;)Lcom/arkivanov/decompose/DefaultComponentContext;
+ public static synthetic fun defaultComponentContext$default (Landroidx/savedstate/SavedStateRegistryOwner;ZLkotlin/jvm/functions/Function0;ILjava/lang/Object;)Lcom/arkivanov/decompose/DefaultComponentContext;
 }
 
 public abstract interface annotation class com/arkivanov/decompose/ExperimentalDecomposeApi : java/lang/annotation/Annotation {

decompose/build.gradle.kts

@@ -58,5 +58,9 @@ kotlin {
  implementation(deps.androidx.fragment.fragmentKtx)
  implementation(deps.androidx.lifecycle.lifecycleCommonJava8)
  }
+
+ android.test.dependencies {
+ implementation(deps.robolectric.robolectric)
+ }
  }
 }

decompose/src/androidMain/kotlin/com/arkivanov/decompose/DefaultComponentContextBuilder.kt

@@ -10,8 +10,11 @@ import androidx.savedstate.SavedStateRegistry
 import androidx.savedstate.SavedStateRegistryOwner
 import com.arkivanov.essenty.backhandler.BackHandler
 import com.arkivanov.essenty.instancekeeper.InstanceKeeper
+import com.arkivanov.essenty.instancekeeper.instanceKeeper
 import com.arkivanov.essenty.lifecycle.asEssentyLifecycle
 import com.arkivanov.essenty.statekeeper.StateKeeper
+import com.arkivanov.essenty.statekeeper.stateKeeper
+import kotlinx.serialization.builtins.serializer
 import androidx.lifecycle.Lifecycle as AndroidLifecycle
 
 fun DefaultComponentContext(
@@ -30,33 +33,67 @@ fun DefaultComponentContext(
 /**
  * Creates a default implementation of [ComponentContext] and attaches it
  * to the receiver (e.g. an [Activity][android.app.Activity]).
+ *
+ * @param discardSavedState a flag indicating whether any previously saved state should be discarded or not,
+ * default value is `false`. Can be useful for handling deep links in `onCreate`, so that the navigation state
+ * is not restored and initial state from the deep link is applied instead.
+ * @param isStateSavingAllowed called before saving the state. When `true` then the state will be saved,
+ * otherwise it won't. Default value is `true`.
  */
-fun <T> T.defaultComponentContext(): DefaultComponentContext where
+fun <T> T.defaultComponentContext(
+ discardSavedState: Boolean = false,
+ isStateSavingAllowed: () -> Boolean = { true },
+): DefaultComponentContext where
  T : SavedStateRegistryOwner, T : OnBackPressedDispatcherOwner, T : ViewModelStoreOwner, T : LifecycleOwner =
- DefaultComponentContext(
- lifecycle = (this as LifecycleOwner).lifecycle,
- savedStateRegistry = savedStateRegistry,
- viewModelStore = viewModelStore,
- onBackPressedDispatcher = onBackPressedDispatcher,
+ defaultComponentContext(
+ backHandler = BackHandler(onBackPressedDispatcher),
+ discardSavedState = discardSavedState,
+ isStateSavingAllowed = isStateSavingAllowed,
  )
 
 /**
  * Creates a default implementation of [ComponentContext] and attaches it to the [Fragment].
  *
  * @param onBackPressedDispatcher an optional [OnBackPressedDispatcher] for back button handling,
  * or `null` if back button handling is not required. Can be obtained via `requireActivity().onBackPressedDispatcher`.
+ * @param discardSavedState a flag indicating whether any previously saved state should be discarded or not,
+ * default value is `false`. Can be useful for handling deep links in `onCreate`, so that the navigation state
+ * is not restored and initial state from the deep link is applied instead.
+ * @param isStateSavingAllowed called before saving the state. When `true` then the state will be saved,
+ * otherwise it won't. Default value is `true`.
  */
 fun Fragment.defaultComponentContext(
  onBackPressedDispatcher: OnBackPressedDispatcher?,
+ discardSavedState: Boolean = false,
+ isStateSavingAllowed: () -> Boolean = { true },
 ): DefaultComponentContext =
- DefaultComponentContext(
- lifecycle = lifecycle.asEssentyLifecycle(),
- stateKeeper = StateKeeper(savedStateRegistry),
- instanceKeeper = InstanceKeeper(viewModelStore),
+ defaultComponentContext(
  backHandler = onBackPressedDispatcher?.let {
  BackHandler(
  onBackPressedDispatcher = it,
  lifecycleOwner = this,
  )
  },
+ discardSavedState = discardSavedState,
+ isStateSavingAllowed = isStateSavingAllowed,
  )
+
+private fun <T> T.defaultComponentContext(
+ backHandler: BackHandler?,
+ discardSavedState: Boolean,
+ isStateSavingAllowed: () -> Boolean,
+): DefaultComponentContext where
+ T : SavedStateRegistryOwner, T : ViewModelStoreOwner, T : LifecycleOwner {
+ val stateKeeper = stateKeeper(discardSavedState = discardSavedState, isSavingAllowed = isStateSavingAllowed)
+ val marker = stateKeeper.consume(key = KEY_STATE_MARKER, strategy = String.serializer())
+ stateKeeper.register(key = KEY_STATE_MARKER, strategy = String.serializer()) { "marker" }
+
+ return DefaultComponentContext(
+ lifecycle = lifecycle.asEssentyLifecycle(),
+ stateKeeper = stateKeeper,
+ instanceKeeper = instanceKeeper(discardRetainedInstances = marker == null),
+ backHandler = backHandler,
+ )
+}
+
+private const val KEY_STATE_MARKER = "DefaultComponentContext_state_marker"

decompose/src/androidUnitTest/kotlin/com/arkivanov/decompose/DefaultComponentContextBuilderTest.kt

@@ -0,0 +1,192 @@
+package com.arkivanov.decompose
+
+import android.os.Bundle
+import android.os.Parcel
+import androidx.activity.OnBackPressedDispatcher
+import androidx.activity.OnBackPressedDispatcherOwner
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.LifecycleRegistry
+import androidx.lifecycle.ViewModelStore
+import androidx.lifecycle.ViewModelStoreOwner
+import androidx.savedstate.SavedStateRegistry
+import androidx.savedstate.SavedStateRegistryController
+import androidx.savedstate.SavedStateRegistryOwner
+import com.arkivanov.decompose.router.TestInstance
+import com.arkivanov.essenty.backhandler.BackCallback
+import com.arkivanov.essenty.instancekeeper.getOrCreate
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotSame
+import kotlin.test.assertNull
+import kotlin.test.assertSame
+import kotlin.test.assertTrue
+
+@Suppress("TestFunctionName")
+@RunWith(RobolectricTestRunner::class)
+class DefaultComponentContextBuilderTest {
+
+ @Test
+ fun saves_and_restores_state() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext()
+ ctx.stateKeeper.register(key = "key") { "saved_state" }
+
+ owner = owner.recreate()
+ ctx = owner.defaultComponentContext()
+ val restoredState = ctx.stateKeeper.consume<String>(key = "key")
+
+ assertEquals("saved_state", restoredState)
+ }
+
+ @Test
+ fun retains_instances() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext()
+ val instance1 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ owner = owner.recreate()
+ ctx = owner.defaultComponentContext()
+ val instance2 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ assertSame(instance1, instance2)
+ }
+
+ @Test
+ fun GIVEN_isStateSavingAllowed_is_false_on_save_THEN_state_not_saved() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext(isStateSavingAllowed = { false })
+ ctx.stateKeeper.register(key = "key") { "saved_state" }
+
+ owner = owner.recreate()
+ ctx = owner.defaultComponentContext()
+ val restoredState = ctx.stateKeeper.consume<String>(key = "key")
+
+ assertNull(restoredState)
+ }
+
+ @Test
+ fun GIVEN_isStateSavingAllowed_is_false_on_save_THEN_instances_not_retained() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext(isStateSavingAllowed = { false })
+ val instance1 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ owner = owner.recreate()
+ ctx = owner.defaultComponentContext()
+ val instance2 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ assertNotSame(instance1, instance2)
+ }
+
+ @Test
+ fun GIVEN_isStateSavingAllowed_is_false_on_save_THEN_old_instances_destroyed() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext(isStateSavingAllowed = { false })
+ val instance1 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ owner = owner.recreate()
+ owner.defaultComponentContext()
+
+ assertTrue(instance1.isDestroyed)
+ }
+
+ @Test
+ fun GIVEN_discardSavedState_is_true_on_restore_THEN_discards_saved_state() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext()
+ ctx.stateKeeper.register(key = "key") { "saved_state" }
+
+ owner = owner.recreate()
+ ctx = owner.defaultComponentContext(discardSavedState = true)
+ val restoredState = ctx.stateKeeper.consume<String>(key = "key")
+
+ assertNull(restoredState)
+ }
+
+ @Test
+ fun GIVEN_discardSavedState_is_true_on_restore_THEN_instances_not_retained() {
+ var owner = TestOwner()
+ var ctx = owner.defaultComponentContext()
+ val instance1 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ owner = owner.recreate()
+ ctx = owner.defaultComponentContext(discardSavedState = true)
+ val instance2 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ assertNotSame(instance1, instance2)
+ }
+
+ @Test
+ fun GIVEN_discardSavedState_is_true_on_restore_THEN_old_instances_destroyed() {
+ var owner = TestOwner()
+ val ctx = owner.defaultComponentContext()
+ val instance1 = ctx.instanceKeeper.getOrCreate(key = "key", factory = ::TestInstance)
+
+ owner = owner.recreate()
+ owner.defaultComponentContext(discardSavedState = true)
+
+ assertTrue(instance1.isDestroyed)
+ }
+
+ @Test
+ fun GIVEN_enabled_BackCallback_registered_WHEN_onBackPressed_THEN_callback_called() {
+ val owner = TestOwner()
+ val ctx = owner.defaultComponentContext()
+ var isCalled = false
+ ctx.backHandler.register(BackCallback { isCalled = true })
+
+ owner.onBackPressedDispatcher.onBackPressed()
+
+ assertTrue(isCalled)
+ }
+
+ @Test
+ fun GIVEN_disabled_BackCallback_registered_WHEN_onBackPressed_THEN_callback_not_called() {
+ val owner = TestOwner()
+ val ctx = owner.defaultComponentContext()
+ var isCalled = false
+ ctx.backHandler.register(BackCallback(isEnabled = false) { isCalled = true })
+
+ owner.onBackPressedDispatcher.onBackPressed()
+
+ assertFalse(isCalled)
+ }
+
+ private class TestOwner(
+ savedState: Bundle = Bundle(),
+ override val viewModelStore: ViewModelStore = ViewModelStore(),
+ ) : LifecycleOwner, SavedStateRegistryOwner, ViewModelStoreOwner, OnBackPressedDispatcherOwner {
+ private val savedStateRegistryController: SavedStateRegistryController = SavedStateRegistryController.create(this)
+ override val lifecycle: Lifecycle = LifecycleRegistry(this)
+ override val savedStateRegistry: SavedStateRegistry get() = savedStateRegistryController.savedStateRegistry
+ override val onBackPressedDispatcher: OnBackPressedDispatcher = OnBackPressedDispatcher()
+
+ init {
+ savedStateRegistryController.performRestore(savedState)
+ }
+
+ fun recreate(): TestOwner {
+ val bundle = Bundle()
+ savedStateRegistryController.performSave(bundle)
+
+ return TestOwner(savedState = bundle.parcelize().deparcelize(), viewModelStore = viewModelStore)
+ }
+
+ private fun Bundle.parcelize(): ByteArray {
+ val parcel = Parcel.obtain()
+ parcel.writeBundle(this)
+ return parcel.marshall()
+ }
+
+ private fun ByteArray.deparcelize(): Bundle {
+ val parcel = Parcel.obtain()
+ parcel.unmarshall(this, 0, size)
+ parcel.setDataPosition(0)
+
+ return requireNotNull(parcel.readBundle())
+ }
+ }
+}

deps.versions.toml

@@ -2,7 +2,7 @@
 
 decompose = "2.2.0-compose-experimental"
 kotlin = "1.9.20"
-essenty = "2.0.0-dev01"
+essenty = "2.0.0-dev02"
 reaktive = "1.2.3"
 junit = "4.13.2"
 jetbrainsCompose = "1.5.10"
@@ -12,6 +12,7 @@ jetbrainsKotlinxSerialization = "1.6.0"
 jetbrainsBinaryCompatibilityValidator = "0.13.2"
 jetpackCompose = "1.5.0"
 jetpackComposeCompiler = "1.5.4"
+robolectric = "4.9.1"
 androidGradle = "8.0.2"
 androidMaterial = "1.6.1"
 androidPlay = "1.10.3"
@@ -48,6 +49,8 @@ jetbrains-kotlin-serializationGradlePlug = { group = "org.jetbrains.kotlin", nam
 jetbrains-kotlinx-kotlinxSerializationCore = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-core", version.ref = "jetbrainsKotlinxSerialization" }
 jetbrains-kotlinx-kotlinxSerializationJson = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version.ref = "jetbrainsKotlinxSerialization" }
 
+robolectric-robolectric = { group = "org.robolectric", name = "robolectric", version.ref = "robolectric" }
+
 androidx-compose-runtime-runtime = { group = "androidx.compose.runtime", name = "runtime", version.ref = "jetpackCompose" }
 
 android-gradle = { group = "com.android.tools.build", name = "gradle", version.ref = "androidGradle" }