Make fabric parameter always true in renderApplication (#56517)

Summary:

Changelog: [Internal]

Remove the fabric parameter from renderApplication and AppContainer. The parameter
is kept in renderApplication for backwards compatibility but is always treated as
true internally. The legacy Paper renderer path is no longer used.

Reviewed By: javache, huntie

Differential Revision: D101353116

Author: rubennorte

packages/react-native/Libraries/ReactNative/AppContainer-dev.js

@@ -100,7 +100,6 @@ const ReactDevToolsOverlayDeferred = ({
 
 const AppContainer = ({
   children,
-  fabric,
   initialProps,
   internal_excludeInspector = false,
   internal_excludeLogBox = false,
@@ -165,7 +164,7 @@ const AppContainer = ({
 
   if (WrapperComponent != null) {
     innerView = (
-      <WrapperComponent initialProps={initialProps} fabric={fabric === true}>
+      <WrapperComponent initialProps={initialProps}>
         {innerView}
       </WrapperComponent>
     );

packages/react-native/Libraries/ReactNative/AppContainer-prod.js

@@ -17,7 +17,6 @@ import * as React from 'react';
 
 const AppContainer = ({
   children,
-  fabric,
   initialProps,
   rootTag,
   WrapperComponent,
@@ -27,7 +26,7 @@ const AppContainer = ({
 
   if (WrapperComponent != null) {
     innerView = (
-      <WrapperComponent initialProps={initialProps} fabric={fabric === true}>
+      <WrapperComponent initialProps={initialProps}>
         {innerView}
       </WrapperComponent>
     );

packages/react-native/Libraries/ReactNative/AppContainer.js

@@ -15,7 +15,6 @@ import * as React from 'react';
 
 export type Props = Readonly<{
   children?: React.Node,
-  fabric?: boolean,
   rootTag: number | RootTag,
   initialProps?: {...},
   WrapperComponent?: ?React.ComponentType<any>,

packages/react-native/Libraries/ReactNative/AppRegistry.flow.js

@@ -31,7 +31,6 @@ export type AppConfig = {
 export type AppParameters = {
   initialProps: Readonly<{[string]: unknown, ...}>,
   rootTag: RootTag,
-  fabric?: boolean,
 };
 export type Runnable = (
   appParameters: AppParameters,

packages/react-native/Libraries/ReactNative/AppRegistryImpl.js

@@ -94,7 +94,7 @@ export function registerComponent(
       appParameters.rootTag,
       wrapperComponentProvider && wrapperComponentProvider(appParameters),
       rootViewStyleProvider && rootViewStyleProvider(appParameters),
-      appParameters.fabric,
+      true, // fabric - deprecated, always true
       scopedPerformanceLogger,
       appKey === 'LogBox', // is logbox
       appKey,

packages/react-native/Libraries/ReactNative/renderApplication.js

@@ -13,7 +13,6 @@ import type {IPerformanceLogger} from '../Utilities/createPerformanceLogger';
 
 import GlobalPerformanceLogger from '../Utilities/GlobalPerformanceLogger';
 import PerformanceLoggerContext from '../Utilities/PerformanceLoggerContext';
-import warnOnce from '../Utilities/warnOnce';
 import AppContainer from './AppContainer';
 import DisplayMode, {type DisplayModeType} from './DisplayMode';
 import getCachedComponentWithDebugName from './getCachedComponentWithDebugName';
@@ -37,7 +36,9 @@ export default function renderApplication<Props extends Object>(
   rootTag: any,
   WrapperComponent?: ?React.ComponentType<any>,
   rootViewStyle?: ?ViewStyleProp,
-  fabric?: boolean,
+  // Keep this parameter for backwards compatibility only. It is always treated as
+  // true internally.
+  fabric?: true | void,
   scopedPerformanceLogger?: IPerformanceLogger,
   isLogBox?: boolean,
   debugName?: string,
@@ -52,7 +53,6 @@ export default function renderApplication<Props extends Object>(
     <PerformanceLoggerContext.Provider value={performanceLogger}>
       <AppContainer
         rootTag={rootTag}
-        fabric={fabric}
         WrapperComponent={WrapperComponent}
         rootViewStyle={rootViewStyle}
         initialProps={initialProps ?? Object.freeze({})}
@@ -87,32 +87,18 @@ export default function renderApplication<Props extends Object>(
     );
   }
 
-  // We want to have concurrentRoot always enabled when you're on Fabric.
-  const useConcurrentRoot = Boolean(fabric);
-
   performanceLogger.startTimespan('renderApplication_React_render');
-  performanceLogger.setExtra(
-    'usedReactConcurrentRoot',
-    useConcurrentRoot ? '1' : '0',
-  );
-  performanceLogger.setExtra('usedReactFabric', fabric ? '1' : '0');
+  performanceLogger.setExtra('usedReactConcurrentRoot', '1');
+  performanceLogger.setExtra('usedReactFabric', '1');
   performanceLogger.setExtra(
     'usedReactProfiler',
     Renderer.isProfilingRenderer(),
   );
   Renderer.renderElement({
     element: renderable,
     rootTag,
-    useFabric: Boolean(fabric),
-    useConcurrentRoot,
+    useFabric: true,
+    useConcurrentRoot: true,
   });
-
-  const newArchitecture = !!fabric;
-  if (!newArchitecture) {
-    warnOnce(
-      '[OSS][OldArchDeprecatedWarning]',
-      'The app is running using the Legacy Architecture. The Legacy Architecture is deprecated and will be removed in a future version of React Native. Please consider migrating to the New Architecture. For more information, please see https://reactnative.dev/blog/2024/10/23/the-new-architecture-is-here',
-    );
-  }
   performanceLogger.stopTimespan('renderApplication_React_render');
 }

packages/react-native/ReactNativeApi.d.ts

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<c018df63c1391fd6906f66f9bb80bb27>>
+ * @generated SignedSource<<ad3edd7df03c5d97bc1bbfc138e3b283>>
  *
  * This file was generated by scripts/js-api/build-types/index.js.
  */
@@ -1638,7 +1638,6 @@ declare type AppearancePreferences = {
   colorScheme?: ColorSchemeName
 }
 declare type AppParameters = {
-  fabric?: boolean
   initialProps: {
     readonly [$$Key$$: string]: unknown
   }
@@ -6013,8 +6012,8 @@ export {
   AlertType, // 5ab91217
   AndroidKeyboardEvent, // e03becc8
   Animated, // a77a3944
-  AppConfig, // ebddad4b
-  AppRegistry, // f7a253e4
+  AppConfig, // ce4209a7
+  AppRegistry, // 5edf0524
   AppState, // 12012be5
   AppStateEvent, // 80f034c3
   AppStateStatus, // 447e5ef2
@@ -6183,15 +6182,15 @@ export {
   RefreshControlProps, // e747ed5d
   RefreshControlPropsAndroid, // 99f64c97
   RefreshControlPropsIOS, // 72a36381
-  Registry, // e1ed403e
+  Registry, // 6c39216d
   ResponderSyntheticEvent, // fb10247c
   ReturnKeyTypeOptions, // afd47ba3
   Role, // af7b889d
   RootTag, // 3cd10504
   RootTagContext, // 38bfc8f6
   RootViewStyleProvider, // d4818465
-  Runnable, // 2cb32c54
-  Runnables, // d3749ae1
+  Runnable, // 594dd93a
+  Runnables, // 4367c557
   SafeAreaView, // 9589fa67
   ScaledSize, // 07e417c7
   ScrollEvent, // 5d529218