Clean interface for public instances between React and React Native (#26416)

## Summary

We are going to move the definition of public instances from React to
React Native to have them together with the native methods in Fabric
that they invoke. This will allow us to have a better type safety
between them and iterate faster on the implementation of this proposal:
https://github.com/react-native-community/discussions-and-proposals/pull/607

The interface between React and React Native would look like this after
this change and a following PR (#26418):

React → React Native:
```javascript
ReactNativePrivateInterface.createPublicInstance // to provide via refs
ReactNativePrivateInterface.getNodeFromPublicInstance // for DevTools, commands, etc.
ReactNativePrivateInterface.getNativeTagFromPublicInstance // to implement `findNodeHandle`
```

React Native → React (ReactFabric):
```javascript
ReactFabric.getNodeFromInternalInstanceHandle // to get most recent node to call into native
ReactFabric.getPublicInstanceFromInternalInstanceHandle // to get public instances from results from native
```

## How did you test this change?

Flow
Existing unit tests

packages/react-native-renderer/src/ReactFabric.js

@@ -40,6 +40,7 @@ import {
   sendAccessibilityEvent,
   getNodeFromInternalInstanceHandle,
 } from './ReactNativePublicCompat';
+import {getPublicInstanceFromInternalInstanceHandle} from './ReactFabricHostConfig';
 
 // $FlowFixMe[missing-local-annot]
 function onRecoverableError(error) {
@@ -124,6 +125,10 @@ export {
   // This method allows it to acess the most recent shadow node for
   // the instance (it's only accessible through it).
   getNodeFromInternalInstanceHandle,
+  // Fabric native methods to traverse the host tree return the same internal
+  // instance handles we use to dispatch events. This provides a way to access
+  // the public instances we created from them (potentially created lazily).
+  getPublicInstanceFromInternalInstanceHandle,
 };
 
 injectIntoDevTools({

packages/react-native-renderer/src/ReactFabricHostConfig.js

@@ -241,6 +241,13 @@ export function getPublicInstance(instance: Instance): null | PublicInstance {
   return null;
 }
 
+export function getPublicInstanceFromInternalInstanceHandle(
+  internalInstanceHandle: Object,
+): null | PublicInstance {
+  const instance: Instance = internalInstanceHandle.stateNode;
+  return getPublicInstance(instance);
+}
+
 export function prepareForCommit(containerInfo: Container): null | Object {
   // Noop
   return null;

packages/react-native-renderer/src/ReactFabricPublicInstanceUtils.js

@@ -8,6 +8,7 @@
  */
 
 import type {ReactFabricHostComponent} from './ReactFabricPublicInstance';
+import {getNodeFromInternalInstanceHandle} from './ReactNativePublicCompat';
 
 /**
  * IMPORTANT: This module is used in Paper and Fabric. It needs to be defined
@@ -22,8 +23,14 @@ export function getNativeTagFromPublicInstance(
   return publicInstance.__nativeTag;
 }
 
-export function getInternalInstanceHandleFromPublicInstance(
+export function getNodeFromPublicInstance(
   publicInstance: ReactFabricHostComponent,
 ): mixed {
-  return publicInstance.__internalInstanceHandle;
+  if (publicInstance.__internalInstanceHandle == null) {
+    return null;
+  }
+
+  return getNodeFromInternalInstanceHandle(
+    publicInstance.__internalInstanceHandle,
+  );
 }

packages/react-native-renderer/src/ReactNativeFiberInspector.js

@@ -20,7 +20,7 @@ import {HostComponent} from 'react-reconciler/src/ReactWorkTags';
 import {UIManager} from 'react-native/Libraries/ReactPrivate/ReactNativePrivateInterface';
 import {enableGetInspectorDataForInstanceInProduction} from 'shared/ReactFeatureFlags';
 import {getClosestInstanceFromNode} from './ReactNativeComponentTree';
-import {getInternalInstanceHandleFromPublicInstance} from './ReactFabricPublicInstanceUtils';
+import {getNodeFromPublicInstance} from './ReactFabricPublicInstanceUtils';
 import {getNodeFromInternalInstanceHandle} from './ReactNativePublicCompat';
 
 const emptyObject = {};
@@ -196,12 +196,7 @@ function getInspectorDataForViewAtPoint(
   if (__DEV__) {
     let closestInstance = null;
 
-    const fabricInstanceHandle =
-      getInternalInstanceHandleFromPublicInstance(inspectedView);
-    const fabricNode =
-      fabricInstanceHandle != null
-        ? getNodeFromInternalInstanceHandle(fabricInstanceHandle)
-        : null;
+    const fabricNode = getNodeFromPublicInstance(inspectedView);
     if (fabricNode) {
       // For Fabric we can look up the instance handle directly and measure it.
       nativeFabricUIManager.findNodeAtPoint(

packages/react-native-renderer/src/ReactNativePublicCompat.js

@@ -24,7 +24,7 @@ import ReactSharedInternals from 'shared/ReactSharedInternals';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 
 import {
-  getInternalInstanceHandleFromPublicInstance,
+  getNodeFromPublicInstance,
   getNativeTagFromPublicInstance,
 } from './ReactFabricPublicInstanceUtils';
 
@@ -176,14 +176,10 @@ export function dispatchCommand(
     return;
   }
 
-  const internalInstanceHandle =
-    getInternalInstanceHandleFromPublicInstance(handle);
+  const node = getNodeFromPublicInstance(handle);
 
-  if (internalInstanceHandle != null) {
-    const node = getNodeFromInternalInstanceHandle(internalInstanceHandle);
-    if (node != null) {
-      nativeFabricUIManager.dispatchCommand(node, command, args);
-    }
+  if (node != null) {
+    nativeFabricUIManager.dispatchCommand(node, command, args);
   } else {
     UIManager.dispatchViewManagerCommand(nativeTag, command, args);
   }
@@ -204,13 +200,9 @@ export function sendAccessibilityEvent(handle: any, eventType: string) {
     return;
   }
 
-  const internalInstanceHandle =
-    getInternalInstanceHandleFromPublicInstance(handle);
-  if (internalInstanceHandle != null) {
-    const node = getNodeFromInternalInstanceHandle(internalInstanceHandle);
-    if (node != null) {
-      nativeFabricUIManager.sendAccessibilityEvent(node, eventType);
-    }
+  const node = getNodeFromPublicInstance(handle);
+  if (node != null) {
+    nativeFabricUIManager.sendAccessibilityEvent(node, eventType);
   } else {
     legacySendAccessibilityEvent(nativeTag, eventType);
   }

packages/react-native-renderer/src/ReactNativeTypes.js

@@ -213,6 +213,8 @@ export type ReactNativeType = {
 };
 
 export opaque type Node = mixed;
+type InternalInstanceHandle = mixed;
+type PublicInstance = mixed;
 
 export type ReactFabricType = {
   findHostInstance_DEPRECATED<TElementType: ElementType>(
@@ -237,7 +239,12 @@ export type ReactFabricType = {
     concurrentRoot: ?boolean,
   ): ?ElementRef<ElementType>,
   unmountComponentAtNode(containerTag: number): void,
-  getNodeFromInternalInstanceHandle(internalInstanceHandle: mixed): ?Node,
+  getNodeFromInternalInstanceHandle(
+    internalInstanceHandle: InternalInstanceHandle,
+  ): ?Node,
+  getPublicInstanceFromInternalInstanceHandle(
+    internalInstanceHandle: InternalInstanceHandle,
+  ): PublicInstance,
   ...
 };
 

packages/react-native-renderer/src/__tests__/ReactFabric-test.internal.js

@@ -16,7 +16,7 @@ let createReactNativeComponentClass;
 let StrictMode;
 let act;
 let getNativeTagFromPublicInstance;
-let getInternalInstanceHandleFromPublicInstance;
+let getNodeFromPublicInstance;
 
 const DISPATCH_COMMAND_REQUIRES_HOST_COMPONENT =
   "Warning: dispatchCommand was called with a ref that isn't a " +
@@ -44,8 +44,8 @@ describe('ReactFabric', () => {
         .ReactNativeViewConfigRegistry.register;
     getNativeTagFromPublicInstance =
       require('../ReactFabricPublicInstanceUtils').getNativeTagFromPublicInstance;
-    getInternalInstanceHandleFromPublicInstance =
-      require('../ReactFabricPublicInstanceUtils').getInternalInstanceHandleFromPublicInstance;
+    getNodeFromPublicInstance =
+      require('../ReactFabricPublicInstanceUtils').getNodeFromPublicInstance;
 
     act = require('internal-test-utils').act;
   });
@@ -1032,10 +1032,7 @@ describe('ReactFabric', () => {
       nativeFabricUIManager.createNode.mock.results[0].value;
     expect(expectedShadowNode).toEqual(expect.any(Object));
 
-    const internalInstanceHandle =
-      getInternalInstanceHandleFromPublicInstance(viewRef);
-    expect(
-      ReactFabric.getNodeFromInternalInstanceHandle(internalInstanceHandle),
-    ).toBe(expectedShadowNode);
+    const node = getNodeFromPublicInstance(viewRef);
+    expect(node).toBe(expectedShadowNode);
   });
 });