Inherit the exception handler in ViewContentCodeBinding's scope

redwood-treehouse-host/src/commonMain/kotlin/app/cash/redwood/treehouse/TreehouseAppContent.kt

@@ -320,7 +320,7 @@ private class ViewContentCodeBinding<A : AppService>(
   private val uiConfigurationFlow = SequentialStateFlow(firstUiConfiguration)
 
   private val bindingScope = CoroutineScope(
-    SupervisorJob(codeSession.scope.coroutineContext.job),
+    codeSession.scope.coroutineContext + SupervisorJob(codeSession.scope.coroutineContext.job),
   )
 
   /** Only accessed on [TreehouseDispatchers.ui]. Null before [initView] and after [cancel]. */

redwood-treehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/FakeProtocolNode.kt

@@ -17,7 +17,10 @@ package app.cash.redwood.treehouse
 
 import app.cash.redwood.RedwoodCodegenApi
 import app.cash.redwood.protocol.ChildrenTag
+import app.cash.redwood.protocol.Event
 import app.cash.redwood.protocol.EventSink
+import app.cash.redwood.protocol.EventTag
+import app.cash.redwood.protocol.Id
 import app.cash.redwood.protocol.PropertyChange
 import app.cash.redwood.protocol.widget.ProtocolChildren
 import app.cash.redwood.protocol.widget.ProtocolNode
@@ -32,6 +35,9 @@ internal class FakeProtocolNode : ProtocolNode<FakeWidget>() {
 
   override fun apply(change: PropertyChange, eventSink: EventSink) {
     widget.label = (change.value as JsonPrimitive).content
+    widget.onClick = {
+      eventSink.sendEvent(Event(Id(1), EventTag(1)))
+    }
   }
 
   override fun children(tag: ChildrenTag): ProtocolChildren<FakeWidget>? {

redwood-treehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/FakeWidget.kt

@@ -25,4 +25,5 @@ class FakeWidget : Widget<FakeWidget> {
   override var modifier: Modifier = Modifier
 
   var label: String? = null
+  var onClick: (() -> Unit)? = null
 }

redwood-treehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/FakeZiplineTreehouseUi.kt

@@ -37,6 +37,7 @@ class FakeZiplineTreehouseUi(
   private val eventLog: EventLog,
 ) : ZiplineTreehouseUi {
   private var nextWidgetId = 1
+  private var messageToThrowOnNextEvent: String? = null
 
   private lateinit var host: ZiplineTreehouseUi.Host
   private val extraServicesToClose = mutableListOf<CancellableService>()
@@ -57,8 +58,18 @@ class FakeZiplineTreehouseUi(
     )
   }
 
+  fun throwOnNextEvent(message: String) {
+    messageToThrowOnNextEvent = message
+  }
+
   override fun sendEvent(event: Event) {
-    eventLog += "$name.sendEvent($event)"
+    eventLog += "$name.sendEvent()"
+
+    val toThrow = messageToThrowOnNextEvent
+    if (toThrow != null) {
+      messageToThrowOnNextEvent = null
+      throw Exception(toThrow)
+    }
   }
 
   fun addBackHandler(isEnabled: Boolean): CancellableService {

redwood-treehouse-host/src/commonTest/kotlin/app/cash/redwood/treehouse/TreehouseAppContentTest.kt

@@ -84,6 +84,9 @@ class TreehouseAppContentTest {
     eventLog.takeEvent("codeListener.onCodeLoaded(view1, initial = true)")
     assertThat(view1.children.single().value.label).isEqualTo("hello")
 
+    view1.children.single().value.onClick!!.invoke()
+    eventLog.takeEvent("codeSessionA.app.uis[0].sendEvent()")
+
     content.unbind()
     eventLog.takeEvent("codeSessionA.app.uis[0].close()")
   }
@@ -418,6 +421,31 @@ class TreehouseAppContentTest {
     content.unbind()
   }
 
+  @Test
+  fun bind_session_addWidget_eventException_unbind() = runTest {
+    val content = treehouseAppContent()
+
+    val view1 = treehouseView("view1")
+    content.bind(view1)
+    eventLog.takeEvent("codeListener.onInitialCodeLoading(view1)")
+
+    val codeSessionA = codeHost.startCodeSession("codeSessionA")
+    eventLog.takeEvent("codeSessionA.start()")
+    eventLog.takeEvent("codeSessionA.app.uis[0].start()")
+
+    codeSessionA.appService.uis.single().addWidget("hello")
+    eventLog.takeEvent("codeListener.onCodeLoaded(view1, initial = true)")
+
+    codeSessionA.appService.uis.single().throwOnNextEvent("boom!")
+    view1.children.single().value.onClick!!.invoke()
+    eventLog.takeEvent("codeSessionA.app.uis[0].sendEvent()")
+    eventLog.takeEvent("codeListener.onUncaughtException(view1, kotlin.Exception: boom!)")
+    eventLog.takeEvent("codeSessionA.app.uis[0].close()")
+    eventLog.takeEvent("codeSessionA.stop()")
+
+    content.unbind()
+  }
+
   private fun treehouseAppContent(): TreehouseAppContent<FakeAppService> {
     return TreehouseAppContent(
       codeHost = codeHost,