Make TreehouseAppContent#preload idempotent (#1713)

cashapp · Nov 30, 2023 · b0e57a4 · b0e57a4
1 parent bb8f233
commit b0e57a4
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Showing 2 changed files with 19 additions and 1 deletion.
diff --git a/...od-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/TreehouseAppContent.kt b/...od-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/TreehouseAppContent.kt
@@ -49,7 +49,7 @@ private class State<A : AppService>(
 private sealed interface ViewState {
   object None : ViewState
 
-  class Preloading(
+  data class Preloading(
     val onBackPressedDispatcher: OnBackPressedDispatcher,
     val uiConfiguration: UiConfiguration,
   ) : ViewState
@@ -87,6 +87,7 @@ internal class TreehouseAppContent<A : AppService>(
     dispatchers.checkUi()
     val previousState = stateFlow.value
 
+    if (previousState.viewState == ViewState.Preloading(onBackPressedDispatcher, uiConfiguration)) return // Idempotent.
     check(previousState.viewState is ViewState.None)
 
     val nextViewState = ViewState.Preloading(onBackPressedDispatcher, uiConfiguration)

diff --git a/...reehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/TreehouseAppContentTest.kt b/...reehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/TreehouseAppContentTest.kt
@@ -446,6 +446,23 @@ class TreehouseAppContentTest {
     content.unbind()
   }
 
+  @Test
+  fun preload_idempotent() = runTest {
+    val content = treehouseAppContent()
+
+    codeHost.startCodeSession("codeSessionA")
+    eventLog.takeEvent("codeSessionA.start()")
+
+    content.preload(onBackPressedDispatcher, uiConfiguration)
+    eventLog.takeEvent("codeSessionA.app.uis[0].start()")
+
+    content.preload(onBackPressedDispatcher, uiConfiguration)
+    eventLog.assertNoEvents()
+
+    content.unbind()
+    eventLog.takeEvent("codeSessionA.app.uis[0].close()")
+  }
+
   @Test
   fun bind_idempotent() = runTest {
     val content = treehouseAppContent()