Clean up feature flag to use lazy public instances in Fabric (facebook#33943)

## Summary

We have thoroughly tested this flag in production and proved stability
and performance, so we can clean it up and "ship it".

Author: rubennorte

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

@@ -66,10 +66,7 @@ import {
   getInspectorDataForInstance,
 } from './ReactNativeFiberInspector';
 
-import {
-  passChildrenWhenCloningPersistedNodes,
-  enableLazyPublicInstanceInFabric,
-} from 'shared/ReactFeatureFlags';
+import {passChildrenWhenCloningPersistedNodes} from 'shared/ReactFeatureFlags';
 import {REACT_CONTEXT_TYPE} from 'shared/ReactSymbols';
 import type {ReactContext} from 'shared/ReactTypes';
 
@@ -204,37 +201,17 @@ export function createInstance(
     internalInstanceHandle, // internalInstanceHandle
   );
 
-  if (enableLazyPublicInstanceInFabric) {
-    return {
-      node: node,
-      canonical: {
-        nativeTag: tag,
-        viewConfig,
-        currentProps: props,
-        internalInstanceHandle,
-        publicInstance: null,
-        publicRootInstance: rootContainerInstance.publicInstance,
-      },
-    };
-  } else {
-    const component = createPublicInstance(
-      tag,
+  return {
+    node: node,
+    canonical: {
+      nativeTag: tag,
       viewConfig,
+      currentProps: props,
       internalInstanceHandle,
-      rootContainerInstance.publicInstance,
-    );
-
-    return {
-      node: node,
-      canonical: {
-        nativeTag: tag,
-        viewConfig,
-        currentProps: props,
-        internalInstanceHandle,
-        publicInstance: component,
-      },
-    };
-  }
+      publicInstance: null,
+      publicRootInstance: rootContainerInstance.publicInstance,
+    },
+  };
 }
 
 export function createTextInstance(

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

@@ -15,6 +15,7 @@ import {
   ReactNativeViewConfigRegistry,
   UIManager,
   deepFreezeAndThrowOnMutationInDev,
+  createPublicInstance,
   type PublicRootInstance,
 } from 'react-native/Libraries/ReactPrivate/ReactNativePrivateInterface';
 
@@ -285,8 +286,26 @@ export function getChildHostContext(
 
 export function getPublicInstance(instance: Instance): PublicInstance {
   // $FlowExpectedError[prop-missing] For compatibility with Fabric
-  if (instance.canonical != null && instance.canonical.publicInstance != null) {
-    // $FlowFixMe[incompatible-return]
+  if (instance.canonical != null) {
+    if (instance.canonical.publicInstance == null) {
+      // $FlowExpectedError[incompatible-use]
+      instance.canonical.publicInstance = createPublicInstance(
+        // $FlowExpectedError[incompatible-use]
+        instance.canonical.nativeTag,
+        // $FlowExpectedError[incompatible-use]
+        instance.canonical.viewConfig,
+        // $FlowExpectedError[incompatible-use]
+        instance.canonical.internalInstanceHandle,
+        // $FlowExpectedError[incompatible-use]
+        instance.canonical.publicRootInstance ?? null,
+      );
+      // This was only necessary to create the public instance.
+      // $FlowExpectedError[prop-missing]
+      instance.canonical.publicRootInstance = null;
+    }
+
+    // $FlowExpectedError[prop-missing]
+    // $FlowExpectedError[incompatible-return]
     return instance.canonical.publicInstance;
   }
 

packages/shared/ReactFeatureFlags.js

@@ -151,8 +151,6 @@ export const transitionLaneExpirationMs = 5000;
  */
 export const enableInfiniteRenderLoopDetection = false;
 
-export const enableLazyPublicInstanceInFabric = false;
-
 export const enableFragmentRefs = __EXPERIMENTAL__;
 
 // -----------------------------------------------------------------------------

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

@@ -23,7 +23,6 @@ export const enableHiddenSubtreeInsertionEffectCleanup = __VARIANT__;
 export const enablePersistedModeClonedFlag = __VARIANT__;
 export const enableEagerAlternateStateNodeCleanup = __VARIANT__;
 export const passChildrenWhenCloningPersistedNodes = __VARIANT__;
-export const enableLazyPublicInstanceInFabric = __VARIANT__;
 export const renameElementSymbol = __VARIANT__;
 export const enableFragmentRefs = __VARIANT__;
 export const enableComponentPerformanceTrack = __VARIANT__;

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

@@ -25,7 +25,6 @@ export const {
   enablePersistedModeClonedFlag,
   enableEagerAlternateStateNodeCleanup,
   passChildrenWhenCloningPersistedNodes,
-  enableLazyPublicInstanceInFabric,
   renameElementSymbol,
   enableFragmentRefs,
 } = dynamicFlags;

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

@@ -64,7 +64,6 @@ export const enableYieldingBeforePassive = false;
 export const enableThrottledScheduling = false;
 export const enableViewTransition = false;
 export const enableGestureTransition = false;
-export const enableLazyPublicInstanceInFabric = false;
 export const enableScrollEndPolyfill = true;
 export const enableSuspenseyImages = false;
 export const enableFizzBlockingRender = true;

packages/shared/forks/ReactFeatureFlags.test-renderer.js

@@ -66,7 +66,6 @@ export const enableYieldingBeforePassive = true;
 export const enableThrottledScheduling = false;
 export const enableViewTransition = false;
 export const enableGestureTransition = false;
-export const enableLazyPublicInstanceInFabric = false;
 export const enableScrollEndPolyfill = true;
 export const enableSuspenseyImages = false;
 export const enableFizzBlockingRender = true;

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

@@ -62,7 +62,6 @@ export const enableYieldingBeforePassive = false;
 export const enableThrottledScheduling = false;
 export const enableViewTransition = false;
 export const enableGestureTransition = false;
-export const enableLazyPublicInstanceInFabric = false;
 export const enableScrollEndPolyfill = true;
 export const enableSuspenseyImages = false;
 export const enableFizzBlockingRender = true;

packages/shared/forks/ReactFeatureFlags.test-renderer.www.js

@@ -74,7 +74,6 @@ export const enableYieldingBeforePassive = false;
 export const enableThrottledScheduling = false;
 export const enableViewTransition = false;
 export const enableGestureTransition = false;
-export const enableLazyPublicInstanceInFabric = false;
 export const enableScrollEndPolyfill = true;
 export const enableSuspenseyImages = false;
 export const enableFizzBlockingRender = true;

packages/shared/forks/ReactFeatureFlags.www-dynamic.js

@@ -31,7 +31,6 @@ export const enableSchedulingProfiler = __VARIANT__;
 export const enableInfiniteRenderLoopDetection = __VARIANT__;
 
 export const enableFastAddPropertiesInDiffing = __VARIANT__;
-export const enableLazyPublicInstanceInFabric = false;
 export const enableViewTransition = __VARIANT__;
 export const enableComponentPerformanceTrack = __VARIANT__;
 export const enableScrollEndPolyfill = __VARIANT__;