[RN] Set up test to create public instances lazily in Fabric

Author: rubennorte

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

@@ -57,7 +57,10 @@ import {
   getInspectorDataForInstance,
 } from './ReactNativeFiberInspector';
 
-import {passChildrenWhenCloningPersistedNodes} from 'shared/ReactFeatureFlags';
+import {
+  passChildrenWhenCloningPersistedNodes,
+  enableLazyPublicInstanceInFabric,
+} from 'shared/ReactFeatureFlags';
 import {REACT_CONTEXT_TYPE} from 'shared/ReactSymbols';
 import type {ReactContext} from 'shared/ReactTypes';
 
@@ -93,8 +96,10 @@ export type Instance = {
     currentProps: Props,
     // Reference to the React handle (the fiber)
     internalInstanceHandle: InternalInstanceHandle,
-    // Exposed through refs.
-    publicInstance: PublicInstance,
+    // Exposed through refs. Potentially lazily created.
+    publicInstance: ?PublicInstance,
+    // This is only necessary to lazily create `publicInstance`.
+    publicRootInstance: ?PublicRootInstance,
   },
 };
 export type TextInstance = {
@@ -186,23 +191,37 @@ export function createInstance(
     internalInstanceHandle, // internalInstanceHandle
   );
 
-  const component = createPublicInstance(
-    tag,
-    viewConfig,
-    internalInstanceHandle,
-    rootContainerInstance.publicInstance,
-  );
-
-  return {
-    node: node,
-    canonical: {
-      nativeTag: tag,
+  if (enableLazyPublicInstanceInFabric) {
+    return {
+      node: node,
+      canonical: {
+        nativeTag: tag,
+        viewConfig,
+        currentProps: props,
+        internalInstanceHandle,
+        publicInstance: null,
+        publicRootInstance: rootContainerInstance.publicInstance,
+      },
+    };
+  } else {
+    const component = createPublicInstance(
+      tag,
       viewConfig,
-      currentProps: props,
       internalInstanceHandle,
-      publicInstance: component,
-    },
-  };
+      rootContainerInstance.publicInstance,
+    );
+
+    return {
+      node: node,
+      canonical: {
+        nativeTag: tag,
+        viewConfig,
+        currentProps: props,
+        internalInstanceHandle,
+        publicInstance: component,
+      },
+    };
+  }
 }
 
 export function createTextInstance(
@@ -277,7 +296,18 @@ export function getChildHostContext(
 }
 
 export function getPublicInstance(instance: Instance): null | PublicInstance {
-  if (instance.canonical != null && instance.canonical.publicInstance != null) {
+  if (instance.canonical != null) {
+    if (instance.canonical.publicInstance == null) {
+      instance.canonical.publicInstance = createPublicInstance(
+        instance.canonical.nativeTag,
+        instance.canonical.viewConfig,
+        instance.canonical.internalInstanceHandle,
+        instance.canonical.publicRootInstance,
+      );
+      // This was only necessary to create the public instance.
+      instance.canonical.publicRootInstance = null;
+    }
+
     return instance.canonical.publicInstance;
   }
 

packages/shared/ReactFeatureFlags.js

@@ -154,6 +154,8 @@ export const enableUseEffectCRUDOverload = false;
 
 export const enableFastAddPropertiesInDiffing = true;
 
+export const enableLazyPublicInstanceInFabric = false;
+
 // -----------------------------------------------------------------------------
 // Ready for next major.
 //

packages/shared/forks/ReactFeatureFlags.native-fb-dynamic.js

@@ -28,3 +28,4 @@ export const enableUseEffectCRUDOverload = __VARIANT__;
 export const enableOwnerStacks = __VARIANT__;
 export const enableRemoveConsolePatches = __VARIANT__;
 export const enableFastAddPropertiesInDiffing = __VARIANT__;
+export const enableLazyPublicInstanceInFabric = __VARIANT__;

packages/shared/forks/ReactFeatureFlags.native-fb.js

@@ -30,6 +30,7 @@ export const {
   enableOwnerStacks,
   enableRemoveConsolePatches,
   enableFastAddPropertiesInDiffing,
+  enableLazyPublicInstanceInFabric,
 } = dynamicFlags;
 
 // The rest of the flags are static for better dead code elimination.