Expose instance handles from shadow nodes directly, instead of from event emitters/targets (#37553)

Summary:
Pull Request resolved: #37553

## Context

I added some getters in EventTarget/EventEmitter to access the React instance handle for a given shadow node/shadow node family in 43864a1 (D44022477), so I could implement DOM traversal methods easily.

I wanted to reuse that method to implement `MutationObserver` and `IntersectionObserver`, but unfortunately `EventEmitter`/`EventTarget` only allow access to the instance handle as long as the shadow node is mounted. That makes sense for events, but not for this use case, as with `MutationObserver` we intentionally want to have access to unmounted nodes when creating the list of `addedNodes` and `removedNodes` for the `MutationRecord` (depending on when exactly we generate this list, either `addedNodes` or `removedNodes` wouldn't be mounted).

## Changes

This reverts my original change and adds a new field in `ShadowNodeFamily` to provide access to the `InstanceHandle` at any point (even if the node isn't mounted).

This provides the same guarantees as the original method, keeping weak references to the handles to avoid memory leaks.

Changelog: [internal]

Reviewed By: sammy-SC

Differential Revision: D46149084

fbshipit-source-id: f76abae50134a5d55a98cab42eebeb62084024f9

Author: rubennorte

packages/react-native/ReactCommon/react/renderer/animations/tests/LayoutAnimationTest.cpp

@@ -56,8 +56,6 @@ static void testShadowNodeTreeLifeCycleLayoutAnimations(
       ViewComponentDescriptor(componentDescriptorParameters);
   auto rootComponentDescriptor =
       RootComponentDescriptor(componentDescriptorParameters);
-  auto noopEventEmitter =
-      std::make_shared<ViewEventEmitter const>(nullptr, -1, eventDispatcher);
 
   PropsParserContext parserContext{-1, *contextContainer};
 
@@ -95,7 +93,7 @@ static void testShadowNodeTreeLifeCycleLayoutAnimations(
     auto surfaceId = SurfaceId(surfaceIdInt);
 
     auto family = rootComponentDescriptor.createFamily(
-        {Tag(surfaceIdInt), surfaceId, nullptr}, nullptr);
+        {Tag(surfaceIdInt), surfaceId, nullptr});
 
     // Creating an initial root shadow node.
     auto emptyRootNode = std::const_pointer_cast<RootShadowNode>(

packages/react-native/ReactCommon/react/renderer/componentregistry/ComponentDescriptorRegistry.cpp

@@ -126,12 +126,13 @@ ShadowNode::Shared ComponentDescriptorRegistry::createNode(
     std::string const &viewName,
     SurfaceId surfaceId,
     folly::dynamic const &propsDynamic,
-    SharedEventTarget const &eventTarget) const {
+    InstanceHandle::Shared const &instanceHandle) const {
   auto unifiedComponentName = componentNameByReactViewName(viewName);
   auto const &componentDescriptor = this->at(unifiedComponentName);
 
-  auto const fragment = ShadowNodeFamilyFragment{tag, surfaceId, nullptr};
-  auto family = componentDescriptor.createFamily(fragment, eventTarget);
+  auto const fragment =
+      ShadowNodeFamilyFragment{tag, surfaceId, instanceHandle};
+  auto family = componentDescriptor.createFamily(fragment);
   auto const props = componentDescriptor.cloneProps(
       PropsParserContext{surfaceId, *contextContainer_.get()},
       nullptr,

packages/react-native/ReactCommon/react/renderer/componentregistry/ComponentDescriptorRegistry.h

@@ -14,6 +14,7 @@
 
 #include <react/renderer/componentregistry/ComponentDescriptorProvider.h>
 #include <react/renderer/core/ComponentDescriptor.h>
+#include <react/renderer/core/InstanceHandle.h>
 #include <react/utils/ContextContainer.h>
 
 namespace facebook::react {
@@ -59,7 +60,7 @@ class ComponentDescriptorRegistry {
       std::string const &viewName,
       SurfaceId surfaceId,
       folly::dynamic const &props,
-      SharedEventTarget const &eventTarget) const;
+      InstanceHandle::Shared const &instanceHandle) const;
 
   void setFallbackComponentDescriptor(
       const SharedComponentDescriptor &descriptor);

packages/react-native/ReactCommon/react/renderer/core/ComponentDescriptor.h

@@ -8,6 +8,8 @@
 #pragma once
 
 #include <react/renderer/core/EventDispatcher.h>
+#include <react/renderer/core/EventEmitter.h>
+#include <react/renderer/core/InstanceHandle.h>
 #include <react/renderer/core/Props.h>
 #include <react/renderer/core/PropsParserContext.h>
 #include <react/renderer/core/RawPropsParser.h>
@@ -136,8 +138,13 @@ class ComponentDescriptor {
    * Creates a shadow node family for particular node.
    */
   virtual ShadowNodeFamily::Shared createFamily(
-      ShadowNodeFamilyFragment const &fragment,
-      SharedEventTarget eventTarget) const = 0;
+      ShadowNodeFamilyFragment const &fragment) const = 0;
+
+  /*
+   * Creates an event emitter for particular node.
+   */
+  virtual SharedEventEmitter createEventEmitter(
+      InstanceHandle::Shared const &instanceHandle) const = 0;
 
  protected:
   EventDispatcher::Weak eventDispatcher_;

packages/react-native/ReactCommon/react/renderer/core/ConcreteComponentDescriptor.h

@@ -180,17 +180,20 @@ class ConcreteComponentDescriptor : public ComponentDescriptor {
   }
 
   ShadowNodeFamily::Shared createFamily(
-      ShadowNodeFamilyFragment const &fragment,
-      SharedEventTarget eventTarget) const override {
-    auto eventEmitter = std::make_shared<ConcreteEventEmitter const>(
-        std::move(eventTarget), fragment.tag, eventDispatcher_);
+      ShadowNodeFamilyFragment const &fragment) const override {
     return std::make_shared<ShadowNodeFamily>(
         ShadowNodeFamilyFragment{
-            fragment.tag, fragment.surfaceId, eventEmitter},
+            fragment.tag, fragment.surfaceId, fragment.instanceHandle},
         eventDispatcher_,
         *this);
   }
 
+  SharedEventEmitter createEventEmitter(
+      InstanceHandle::Shared const &instanceHandle) const override {
+    return std::make_shared<ConcreteEventEmitter const>(
+        std::make_shared<EventTarget>(instanceHandle), eventDispatcher_);
+  }
+
  protected:
   /*
    * Called immediately after `ShadowNode` is created or cloned.

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.cpp

@@ -43,7 +43,6 @@ ValueFactory EventEmitter::defaultPayloadFactory() {
 
 EventEmitter::EventEmitter(
     SharedEventTarget eventTarget,
-    Tag /*tag*/,
     EventDispatcher::Weak eventDispatcher)
     : eventTarget_(std::move(eventTarget)),
       eventDispatcher_(std::move(eventDispatcher)) {}
@@ -131,8 +130,4 @@ void EventEmitter::setEnabled(bool enabled) const {
   }
 }
 
-const SharedEventTarget &EventEmitter::getEventTarget() const {
-  return eventTarget_;
-}
-
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.h

@@ -38,7 +38,6 @@ class EventEmitter {
 
   EventEmitter(
       SharedEventTarget eventTarget,
-      Tag tag,
       EventDispatcher::Weak eventDispatcher);
 
   virtual ~EventEmitter() = default;
@@ -55,8 +54,6 @@ class EventEmitter {
    */
   void setEnabled(bool enabled) const;
 
-  SharedEventTarget const &getEventTarget() const;
-
  protected:
 #ifdef ANDROID
   // We need this temporarily due to lack of Java-counterparts for particular

packages/react-native/ReactCommon/react/renderer/core/EventTarget.cpp

@@ -13,14 +13,9 @@ namespace facebook::react {
 
 using Tag = EventTarget::Tag;
 
-EventTarget::EventTarget(
-    jsi::Runtime &runtime,
-    jsi::Value const &instanceHandle,
-    Tag tag)
-    : weakInstanceHandle_(
-          jsi::WeakObject(runtime, instanceHandle.asObject(runtime))),
-      strongInstanceHandle_(jsi::Value::null()),
-      tag_(tag) {}
+EventTarget::EventTarget(InstanceHandle::Shared instanceHandle)
+    : instanceHandle_(std::move(instanceHandle)),
+      strongInstanceHandle_(jsi::Value::null()) {}
 
 void EventTarget::setEnabled(bool enabled) const {
   enabled_ = enabled;
@@ -31,7 +26,7 @@ void EventTarget::retain(jsi::Runtime &runtime) const {
     return;
   }
 
-  strongInstanceHandle_ = weakInstanceHandle_.lock(runtime);
+  strongInstanceHandle_ = instanceHandle_->getInstanceHandle(runtime);
 
   // Having a `null` or `undefined` object here indicates that
   // `weakInstanceHandle_` was already deallocated. This should *not* happen by
@@ -62,7 +57,7 @@ jsi::Value EventTarget::getInstanceHandle(jsi::Runtime &runtime) const {
 }
 
 Tag EventTarget::getTag() const {
-  return tag_;
+  return instanceHandle_->getTag();
 }
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/EventTarget.h

@@ -7,9 +7,9 @@
 
 #pragma once
 
-#include <memory>
-
 #include <jsi/jsi.h>
+#include <react/renderer/core/InstanceHandle.h>
+#include <memory>
 
 namespace facebook::react {
 
@@ -34,7 +34,7 @@ class EventTarget {
   /*
    * Constructs an EventTarget from a weak instance handler and a tag.
    */
-  EventTarget(jsi::Runtime &runtime, jsi::Value const &instanceHandle, Tag tag);
+  explicit EventTarget(InstanceHandle::Shared instanceHandle);
 
   /*
    * Sets the `enabled` flag that allows creating a strong instance handle from
@@ -65,10 +65,9 @@ class EventTarget {
   Tag getTag() const;
 
  private:
+  const InstanceHandle::Shared instanceHandle_;
   mutable bool enabled_{false}; // Protected by `EventEmitter::DispatchMutex()`.
-  mutable jsi::WeakObject weakInstanceHandle_; // Protected by `jsi::Runtime &`.
   mutable jsi::Value strongInstanceHandle_; // Protected by `jsi::Runtime &`.
-  Tag tag_;
 };
 
 using SharedEventTarget = std::shared_ptr<const EventTarget>;

packages/react-native/ReactCommon/react/renderer/core/InstanceHandle.cpp

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "InstanceHandle.h"
+
+namespace facebook::react {
+
+InstanceHandle::InstanceHandle(
+    jsi::Runtime &runtime,
+    jsi::Value const &instanceHandle,
+    Tag tag)
+    : weakInstanceHandle_(
+          jsi::WeakObject(runtime, instanceHandle.asObject(runtime))),
+      tag_(tag) {}
+
+jsi::Value InstanceHandle::getInstanceHandle(jsi::Runtime &runtime) const {
+  return weakInstanceHandle_.lock(runtime);
+}
+
+Tag InstanceHandle::getTag() const {
+  return tag_;
+}
+
+} // namespace facebook::react