[RTR] Add usage warning behind flag (#27903)

## Summary

Moving towards deprecation of ReactTestRenderer. Log a warning on each
render so we can remove the exports in a future major version.

We can enable this flag in web RTR without disrupting RN tests by
flipping the flag in
`packages/shared/forks/ReactFeatureFlags.test-renderer.js`

## How did you test this change?

`yarn test
packages/react-test-renderer/src/__tests__/ReactTestRenderer-test.js`

packages/react-test-renderer/src/ReactTestRenderer.js

@@ -52,7 +52,10 @@ import {checkPropStringCoercion} from 'shared/CheckStringCoercion';
 
 import {getPublicInstance} from './ReactFiberConfigTestHost';
 import {ConcurrentRoot, LegacyRoot} from 'react-reconciler/src/ReactRootTags';
-import {allowConcurrentByDefault} from 'shared/ReactFeatureFlags';
+import {
+  allowConcurrentByDefault,
+  enableReactTestRendererWarning,
+} from 'shared/ReactFeatureFlags';
 
 const act = React.act;
 
@@ -471,6 +474,14 @@ function create(
   getInstance(): React$Component<any, any> | PublicInstance | null,
   unstable_flushSync: typeof flushSync,
 } {
+  if (__DEV__) {
+    if (enableReactTestRendererWarning === true) {
+      console.warn(
+        'react-test-renderer is deprecated. See https://react.dev/warnings/react-test-renderer',
+      );
+    }
+  }
+
   let createNodeMock = defaultTestOptions.createNodeMock;
   let isConcurrent = false;
   let isStrictMode = false;

packages/react-test-renderer/src/__tests__/ReactTestRenderer-test.internal.js

@@ -51,6 +51,21 @@ function cleanNodeOrArray(node) {
 }
 
 describe('ReactTestRenderer', () => {
+  beforeEach(() => {
+    jest.resetModules();
+    ReactFeatureFlags.enableReactTestRendererWarning = false;
+  });
+
+  it('should warn if enableReactTestRendererWarning is enabled', () => {
+    ReactFeatureFlags.enableReactTestRendererWarning = true;
+    expect(() => {
+      ReactTestRenderer.create(<div />);
+    }).toWarnDev(
+      'Warning: react-test-renderer is deprecated. See https://react.dev/warnings/react-test-renderer',
+      {withoutStack: true},
+    );
+  });
+
   it('renders a simple component', () => {
     function Link() {
       return <a role="link" />;

packages/shared/ReactFeatureFlags.js

@@ -187,6 +187,11 @@ export const enableInfiniteRenderLoopDetection = true;
 // during element creation.
 export const enableRefAsProp = __NEXT_MAJOR__;
 
+// Not ready to break experimental yet.
+// Needs more internal cleanup
+// Warn on any usage of ReactTestRenderer
+export const enableReactTestRendererWarning = false;
+
 // -----------------------------------------------------------------------------
 // Chopping Block
 //

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

@@ -102,5 +102,7 @@ export const enableInfiniteRenderLoopDetection = false;
 // because JSX is an extremely hot path.
 export const enableRefAsProp = false;
 
+export const enableReactTestRendererWarning = false;
+
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);

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

@@ -93,5 +93,7 @@ export const enableServerComponentLogs = true;
 // TODO: Should turn this on in next "major" RN release.
 export const enableRefAsProp = false;
 
+export const enableReactTestRendererWarning = false;
+
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);

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

@@ -98,6 +98,7 @@ export const enableInfiniteRenderLoopDetection = false;
 // flags should be handled by the Fiber config.
 const __NEXT_MAJOR__ = __EXPERIMENTAL__;
 export const enableRefAsProp = __NEXT_MAJOR__;
+export const enableReactTestRendererWarning = false;
 
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);

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

@@ -89,5 +89,7 @@ export const enableServerComponentLogs = true;
 
 export const enableRefAsProp = false;
 
+export const enableReactTestRendererWarning = false;
+
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);

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

@@ -92,5 +92,7 @@ export const enableInfiniteRenderLoopDetection = false;
 
 export const enableRefAsProp = false;
 
+export const enableReactTestRendererWarning = false;
+
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);

packages/shared/forks/ReactFeatureFlags.www.js

@@ -118,5 +118,7 @@ export const disableClientCache = true;
 export const enableServerComponentKeys = true;
 export const enableServerComponentLogs = true;
 
+export const enableReactTestRendererWarning = false;
+
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);