Add a hook to close EventListener.Factory instances (#2280)

* Add a hook to close EventListener.Factory instances

These things potentially hold resources and so should be closeable.

* Track API changes

Author: squarejesse

CHANGELOG.md

@@ -4,7 +4,7 @@
 [Unreleased]: https://github.com/cashapp/redwood/compare/0.13.0...HEAD
 
 New:
-- Nothing yet!
+- `EventListener.Factory.close()` is called by `TreehouseApp.close()` to release any resources held by the factory.
 
 Changed:
 - Nothing yet!

redwood-treehouse-host/api/android/redwood-treehouse-host.api

@@ -64,7 +64,7 @@ public final class app/cash/redwood/treehouse/EventListener$Companion {
 	public final fun getNONE ()Lapp/cash/redwood/treehouse/EventListener$Factory;
 }
 
-public abstract interface class app/cash/redwood/treehouse/EventListener$Factory {
+public abstract interface class app/cash/redwood/treehouse/EventListener$Factory : java/lang/AutoCloseable {
 	public abstract fun create (Lapp/cash/redwood/treehouse/TreehouseApp;Ljava/lang/String;)Lapp/cash/redwood/treehouse/EventListener;
 }
 

redwood-treehouse-host/api/jvm/redwood-treehouse-host.api

@@ -64,7 +64,7 @@ public final class app/cash/redwood/treehouse/EventListener$Companion {
 	public final fun getNONE ()Lapp/cash/redwood/treehouse/EventListener$Factory;
 }
 
-public abstract interface class app/cash/redwood/treehouse/EventListener$Factory {
+public abstract interface class app/cash/redwood/treehouse/EventListener$Factory : java/lang/AutoCloseable {
 	public abstract fun create (Lapp/cash/redwood/treehouse/TreehouseApp;Ljava/lang/String;)Lapp/cash/redwood/treehouse/EventListener;
 }
 

redwood-treehouse-host/api/redwood-treehouse-host.klib.api

@@ -175,7 +175,7 @@ open class app.cash.redwood.treehouse/EventListener { // app.cash.redwood.treeho
     open fun unknownWidget(app.cash.redwood.protocol/WidgetTag) // app.cash.redwood.treehouse/EventListener.unknownWidget|unknownWidget(app.cash.redwood.protocol.WidgetTag){}[0]
     open fun ziplineCreated(app.cash.zipline/Zipline) // app.cash.redwood.treehouse/EventListener.ziplineCreated|ziplineCreated(app.cash.zipline.Zipline){}[0]
 
-    abstract fun interface Factory { // app.cash.redwood.treehouse/EventListener.Factory|null[0]
+    abstract interface Factory : kotlin/AutoCloseable { // app.cash.redwood.treehouse/EventListener.Factory|null[0]
         abstract fun create(app.cash.redwood.treehouse/TreehouseApp<*>, kotlin/String?): app.cash.redwood.treehouse/EventListener // app.cash.redwood.treehouse/EventListener.Factory.create|create(app.cash.redwood.treehouse.TreehouseApp<*>;kotlin.String?){}[0]
     }
 

redwood-treehouse-host/src/appsJvmTest/kotlin/app/cash/redwood/treehouse/LeaksTest.kt

@@ -127,6 +127,25 @@ class LeaksTest {
     eventListenerLeakWatcher.assertNotLeaked()
   }
 
+  @Test
+  fun eventListenerFactoryNotLeaked() = runTest {
+    val tester = TreehouseTester(this)
+    tester.eventListenerFactory = RetainEverythingEventListenerFactory(tester.eventLog)
+    val treehouseApp = tester.loadApp()
+
+    val eventListenerFactoryLeakWatcher = LeakWatcher {
+      tester.eventListenerFactory
+    }
+
+    // Stop referencing our EventListener.Factory from our test harness.
+    tester.eventListenerFactory = FakeEventListener.Factory(tester.eventLog)
+
+    // After close, it's unreachable.
+    treehouseApp.close()
+    eventListenerFactoryLeakWatcher.assertNotLeaked()
+    tester.eventLog.takeEvent("EventListener.Factory.close()", skipOthers = true)
+  }
+
   @Test
   fun contentSourceNotLeaked() = runTest {
     val tester = TreehouseTester(this)

redwood-treehouse-host/src/appsJvmTest/kotlin/app/cash/redwood/treehouse/RetainEverythingEventListenerFactory.kt

@@ -45,4 +45,8 @@ class RetainEverythingEventListenerFactory(
   override fun codeUnloaded() {
     eventLog += "codeUnloaded"
   }
+
+  override fun close() {
+    eventLog += "EventListener.Factory.close()"
+  }
 }

redwood-treehouse-host/src/appsJvmTest/kotlin/app/cash/redwood/treehouse/TreehouseTesterTest.kt

@@ -43,5 +43,6 @@ class TreehouseTesterTest {
     assertThat(buttonValue.text).isEqualTo("This is TreehouseTesterTestHappyPathStep2")
 
     treehouseApp.stop()
+    treehouseApp.close()
   }
 }

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

@@ -106,7 +106,7 @@ internal abstract class CodeHost<A : AppService>(
     codeUpdatesScope.collectCodeUpdates(eventListenerFactory)
   }
 
-  /** This function may only be invoked on [TreehouseDispatchers.zipline]. */
+  /** This function may only be invoked on [TreehouseDispatchers.ui]. */
   fun stop() {
     dispatchers.checkUi()
 

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

@@ -21,7 +21,6 @@ import app.cash.redwood.protocol.Id
 import app.cash.redwood.protocol.ModifierTag
 import app.cash.redwood.protocol.PropertyTag
 import app.cash.redwood.protocol.WidgetTag
-import app.cash.redwood.treehouse.EventListener.Factory
 import app.cash.zipline.Call
 import app.cash.zipline.CallResult
 import app.cash.zipline.Zipline
@@ -367,7 +366,15 @@ public open class EventListener {
   ) {
   }
 
-  public fun interface Factory {
+  /**
+   * Creates new instances of [EventListener].
+   *
+   * A new [EventListener] will be created for each code load attempt: there may be multiple
+   * instances for a single [TreehouseApp] due to hot reloading.
+   *
+   * This factory will be closed when the [TreehouseApp] it belongs to is closed.
+   */
+  public interface Factory : AutoCloseable {
     /**
      * Returns an event listener that receives the events of a specific code session. Each code
      * session includes a single [Zipline] instance, unless code loading fails, in which case there
@@ -380,8 +387,10 @@ public open class EventListener {
   }
 
   public companion object {
-    public val NONE: Factory = Factory { _, _ ->
-      EventListener()
+    public val NONE: Factory = object : Factory {
+      override fun create(app: TreehouseApp<*>, manifestUrl: String?) = EventListener()
+      override fun close() {
+      }
     }
   }
 }

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

@@ -177,6 +177,7 @@ internal class RealTreehouseApp<A : AppService> private constructor(
 
     closed = true
     spec = null
+    eventListenerFactory?.close()
     eventListenerFactory = null
     stop()
     dispatchers.close()