Expose guest Redwood version to host (#1939)

In order to ensure the guest is fully setup such that we can query this, we have to defer creating the host-side bridge until we have received some changes.

Author: JakeWharton

redwood-treehouse-guest/api/android/redwood-treehouse-guest.api

@@ -2,6 +2,7 @@ public final class app/cash/redwood/treehouse/StandardAppLifecycle : app/cash/re
 	public synthetic fun <init> (Lapp/cash/redwood/protocol/guest/ProtocolBridge$Factory;Lkotlinx/serialization/json/Json;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun close ()V
 	public final fun getFrameClock ()Landroidx/compose/runtime/MonotonicFrameClock;
+	public fun getGuestProtocolVersion-7jYel6c ()Ljava/lang/String;
 	public fun sendFrame (J)V
 	public fun start (Lapp/cash/redwood/treehouse/AppLifecycle$Host;)V
 }

redwood-treehouse-guest/api/jvm/redwood-treehouse-guest.api

@@ -2,6 +2,7 @@ public final class app/cash/redwood/treehouse/StandardAppLifecycle : app/cash/re
 	public synthetic fun <init> (Lapp/cash/redwood/protocol/guest/ProtocolBridge$Factory;Lkotlinx/serialization/json/Json;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun close ()V
 	public final fun getFrameClock ()Landroidx/compose/runtime/MonotonicFrameClock;
+	public fun getGuestProtocolVersion-7jYel6c ()Ljava/lang/String;
 	public fun sendFrame (J)V
 	public fun start (Lapp/cash/redwood/treehouse/AppLifecycle$Host;)V
 }

redwood-treehouse-guest/api/redwood-treehouse-guest.klib.api

@@ -12,5 +12,7 @@ final class app.cash.redwood.treehouse/StandardAppLifecycle : app.cash.redwood.t
     final fun start(app.cash.redwood.treehouse/AppLifecycle.Host) // app.cash.redwood.treehouse/StandardAppLifecycle.start|start(app.cash.redwood.treehouse.AppLifecycle.Host){}[0]
     final val frameClock // app.cash.redwood.treehouse/StandardAppLifecycle.frameClock|{}frameClock[0]
         final fun <get-frameClock>(): androidx.compose.runtime/MonotonicFrameClock // app.cash.redwood.treehouse/StandardAppLifecycle.frameClock.<get-frameClock>|<get-frameClock>(){}[0]
+    final val guestProtocolVersion // app.cash.redwood.treehouse/StandardAppLifecycle.guestProtocolVersion|{}guestProtocolVersion[0]
+        final fun <get-guestProtocolVersion>(): app.cash.redwood.protocol/RedwoodVersion // app.cash.redwood.treehouse/StandardAppLifecycle.guestProtocolVersion.<get-guestProtocolVersion>|<get-guestProtocolVersion>(){}[0]
 }
 final fun (app.cash.redwood.treehouse/TreehouseUi).app.cash.redwood.treehouse/asZiplineTreehouseUi(app.cash.redwood.treehouse/StandardAppLifecycle): app.cash.redwood.treehouse/ZiplineTreehouseUi // app.cash.redwood.treehouse/asZiplineTreehouseUi|asZiplineTreehouseUi@app.cash.redwood.treehouse.TreehouseUi(app.cash.redwood.treehouse.StandardAppLifecycle){}[0]

redwood-treehouse-guest/src/commonMain/kotlin/app/cash/redwood/treehouse/StandardAppLifecycle.kt

@@ -23,6 +23,7 @@ import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.redwood.protocol.WidgetTag
 import app.cash.redwood.protocol.guest.ProtocolBridge
 import app.cash.redwood.protocol.guest.ProtocolMismatchHandler
+import app.cash.redwood.protocol.guest.guestRedwoodVersion
 import app.cash.redwood.treehouse.AppLifecycle.Host
 import app.cash.zipline.ZiplineApiMismatchException
 import kotlin.coroutines.CoroutineContext
@@ -38,6 +39,9 @@ public class StandardAppLifecycle(
   private var started = false
   private lateinit var host: Host
 
+  override val guestProtocolVersion: RedwoodVersion
+    get() = guestRedwoodVersion
+
   internal val hostProtocolVersion: RedwoodVersion get() {
     return try {
       host.hostProtocolVersion

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

@@ -15,6 +15,7 @@
  */
 package app.cash.redwood.treehouse
 
+import app.cash.redwood.protocol.RedwoodVersion
 import kotlin.coroutines.CoroutineContext
 import kotlinx.coroutines.CoroutineExceptionHandler
 import kotlinx.coroutines.CoroutineScope
@@ -55,6 +56,8 @@ internal abstract class CodeSession<A : AppService>(
 
   abstract val json: Json
 
+  abstract val guestProtocolVersion: RedwoodVersion
+
   fun start() {
     dispatchers.checkUi()
     scope.launch(dispatchers.zipline) {

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

@@ -18,7 +18,6 @@ package app.cash.redwood.treehouse
 import app.cash.redwood.protocol.Change
 import app.cash.redwood.protocol.Event
 import app.cash.redwood.protocol.EventSink
-import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.redwood.protocol.host.ProtocolBridge
 import app.cash.redwood.protocol.host.ProtocolFactory
 import app.cash.redwood.ui.OnBackPressedCallback
@@ -313,7 +312,10 @@ private class ViewContentCodeBinding<A : AppService>(
   /** Only accessed on [TreehouseDispatchers.ui]. Null before [initView] and after [cancel]. */
   private var viewOrNull: TreehouseView<*>? = null
 
-  /** Only accessed on [TreehouseDispatchers.ui]. Null before [initView] and after [cancel]. */
+  /**
+   * Only accessed on [TreehouseDispatchers.ui].
+   * Null before [initView]+[receiveChangesOnUiDispatcher] and after [cancel].
+   */
   private var bridgeOrNull: ProtocolBridge<*>? = null
 
   /** Only accessed on [TreehouseDispatchers.zipline]. */
@@ -351,18 +353,6 @@ private class ViewContentCodeBinding<A : AppService>(
 
     view.saveCallback = this
 
-    @Suppress("UNCHECKED_CAST") // We don't have a type parameter for the widget type.
-    bridgeOrNull = ProtocolBridge(
-      // TODO Wire through guest version. Wanted this from AppLifecycle but it's bound too late.
-      guestVersion = RedwoodVersion.Unknown,
-      container = view.children as Widget.Children<Any>,
-      factory = view.widgetSystem.widgetFactory(
-        json = codeSession.json,
-        protocolMismatchHandler = eventPublisher.widgetProtocolMismatchHandler,
-      ) as ProtocolFactory<Any>,
-      eventSink = this,
-    )
-
     // Apply all the changes received before we had a view to apply them to.
     while (true) {
       val changes = changesAwaitingInitView.removeFirstOrNull() ?: break
@@ -388,14 +378,12 @@ private class ViewContentCodeBinding<A : AppService>(
   }
 
   private fun receiveChangesOnUiDispatcher(changes: List<Change>) {
-    val view = viewOrNull
-    val bridge = bridgeOrNull
-
     if (canceled) {
       return
     }
 
-    if (view == null || bridge == null) {
+    val view = viewOrNull
+    if (view == null) {
       if (changesAwaitingInitView.isEmpty()) {
         // Unblock coroutines suspended on TreehouseAppContent.awaitContent().
         val currentState = stateFlow.value
@@ -414,6 +402,21 @@ private class ViewContentCodeBinding<A : AppService>(
       return
     }
 
+    var bridge = bridgeOrNull
+    if (bridge == null) {
+      @Suppress("UNCHECKED_CAST") // We don't have a type parameter for the widget type.
+      bridge = ProtocolBridge(
+        guestVersion = codeSession.guestProtocolVersion,
+        container = view.children as Widget.Children<Any>,
+        factory = view.widgetSystem.widgetFactory(
+          json = codeSession.json,
+          protocolMismatchHandler = eventPublisher.widgetProtocolMismatchHandler,
+        ) as ProtocolFactory<Any>,
+        eventSink = this,
+      )
+      bridgeOrNull = bridge
+    }
+
     if (changesCount++ == 0) {
       view.reset()
       codeEventPublisher.onCodeLoaded(view, isInitialLaunch)

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

@@ -15,7 +15,9 @@
  */
 package app.cash.redwood.treehouse
 
+import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.zipline.Zipline
+import app.cash.zipline.ZiplineApiMismatchException
 import app.cash.zipline.ZiplineScope
 import app.cash.zipline.withScope
 import kotlinx.coroutines.CoroutineScope
@@ -35,12 +37,22 @@ internal class ZiplineCodeSession<A : AppService>(
   appService = appService,
 ) {
   private val ziplineScope = ZiplineScope()
+  private lateinit var appLifecycle: AppLifecycle
 
   override val json: Json
     get() = zipline.json
 
+  override val guestProtocolVersion: RedwoodVersion
+    get() {
+      return try {
+        appLifecycle.guestProtocolVersion
+      } catch (_: ZiplineApiMismatchException) {
+        RedwoodVersion.Unknown
+      }
+    }
+
   override fun ziplineStart() {
-    val appLifecycle = appService.withScope(ziplineScope).appLifecycle
+    appLifecycle = appService.withScope(ziplineScope).appLifecycle
 
     val host = RealAppLifecycleHost(
       appLifecycle = appLifecycle,

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

@@ -15,6 +15,7 @@
  */
 package app.cash.redwood.treehouse
 
+import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.redwood.treehouse.AppLifecycle.Host
 import assertk.all
 import assertk.assertThat
@@ -42,6 +43,7 @@ abstract class AbstractFrameClockTest {
 
     val frameTimes = Channel<Long>(Channel.UNLIMITED)
     val appLifecycle = object : AppLifecycle {
+      override val guestProtocolVersion get() = RedwoodVersion.Unknown
       override fun start(host: Host) {
       }
       override fun sendFrame(timeNanos: Long) {

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

@@ -15,6 +15,9 @@
  */
 package app.cash.redwood.treehouse
 
+import app.cash.redwood.protocol.RedwoodVersion
+import app.cash.redwood.protocol.host.hostRedwoodVersion
+
 internal class FakeAppService private constructor(
   private val name: String,
   private val eventLog: EventLog,
@@ -26,6 +29,10 @@ internal class FakeAppService private constructor(
     get() = mutableUis.toList()
 
   override val appLifecycle = object : AppLifecycle {
+    override val guestProtocolVersion: RedwoodVersion
+      // Use latest host version as the guest version to avoid any compatibility behavior.
+      get() = hostRedwoodVersion
+
     override fun start(host: AppLifecycle.Host) {
       eventLog += "$name.appLifecycle.start()"
     }

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

@@ -15,6 +15,8 @@
  */
 package app.cash.redwood.treehouse
 
+import app.cash.redwood.protocol.RedwoodVersion
+import app.cash.redwood.protocol.host.hostRedwoodVersion
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.serialization.json.Json
 
@@ -33,6 +35,10 @@ internal class FakeCodeSession(
   override val json: Json
     get() = Json
 
+  override val guestProtocolVersion: RedwoodVersion
+    // Use latest host version as the guest version to avoid any compatibility behavior.
+    get() = hostRedwoodVersion
+
   override fun ziplineStart() {
     eventLog += "$name.start()"
   }