Only affect OSS for now

Author: eps1lon

packages/react-reconciler/src/__tests__/ReactIsomorphicAct-test.js

@@ -50,9 +50,16 @@ describe('isomorphic act()', () => {
     return text;
   }
 
-  // @gate !__DEV__
-  it('is not exported in production builds', () => {
-    expect(React).not.toHaveProperty('act');
+  it('behavior in production', () => {
+    if (!__DEV__) {
+      if (gate('www')) {
+        expect(() => act(() => {})).toThrow(
+          'act(...) is not supported in production builds of React',
+        );
+      } else {
+        expect(React).not.toHaveProperty('act');
+      }
+    }
   });
 
   // @gate __DEV__

packages/react-reconciler/src/__tests__/ReactOwnerStacks-test.js

@@ -31,6 +31,15 @@ describe('ReactOwnerStacks', () => {
     );
   }
 
+  it('behavior in production', () => {
+    if (!__DEV__) {
+      if (gate('www')) {
+        expect(React.captureOwnerStack()).toEqual(null);
+      } else {
+        expect(React).not.toHaveProperty('act');
+      }
+    }
+  });
   it('is not exported in production buids', () => {
     // awkward to gate because FB builds will have it undefined if disabled
     // whereas OSS builds will have it stripped if disabled because we only have

packages/react/index.fb.development.js

@@ -7,9 +7,12 @@
  * @flow
  */
 
+import {enableOwnerStacks} from 'shared/ReactFeatureFlags';
+import {captureOwnerStack as captureOwnerStackImpl} from './src/ReactClient';
 export {
   __CLIENT_INTERNALS_DO_NOT_USE_OR_WARN_USERS_THEY_CANNOT_UPGRADE,
   __COMPILER_RUNTIME,
+  act,
   cache,
   Children,
   cloneElement,
@@ -67,3 +70,11 @@ export {useMemoCache as unstable_useMemoCache} from './src/ReactHooks';
 // export to match the name of the OSS function typically exported from
 // react/compiler-runtime
 export {useMemoCache as c} from './src/ReactHooks';
+
+// Only export captureOwnerStack in development.
+let captureOwnerStack: ?() => null | string;
+if (__DEV__ && enableOwnerStacks) {
+  captureOwnerStack = captureOwnerStackImpl;
+}
+
+export {captureOwnerStack};