use an explicit export for the sigil

packages/react-dom/src/client/ReactDOM.js

@@ -38,6 +38,7 @@ import {
   findHostInstance,
   findHostInstanceWithWarning,
   flushPassiveEffects,
+  ReactActingRendererSigil,
 } from 'react-reconciler/inline.dom';
 import {createPortal as createPortalImpl} from 'shared/ReactPortal';
 import {canUseDOM} from 'shared/ExecutionEnvironment';
@@ -816,6 +817,7 @@ const ReactDOM: Object = {
       dispatchEvent,
       runEventsInBatch,
       flushPassiveEffects,
+      ReactActingRendererSigil,
     ],
   },
 };

packages/react-dom/src/fire/ReactFire.js

@@ -43,6 +43,7 @@ import {
   findHostInstance,
   findHostInstanceWithWarning,
   flushPassiveEffects,
+  ReactActingRendererSigil,
 } from 'react-reconciler/inline.fire';
 import {createPortal as createPortalImpl} from 'shared/ReactPortal';
 import {canUseDOM} from 'shared/ExecutionEnvironment';
@@ -822,6 +823,7 @@ const ReactDOM: Object = {
       dispatchEvent,
       runEventsInBatch,
       flushPassiveEffects,
+      ReactActingRendererSigil,
     ],
   },
 };

packages/react-dom/src/test-utils/ReactTestUtils.js

@@ -42,8 +42,10 @@ const [
   restoreStateIfNeeded,
   dispatchEvent,
   runEventsInBatch,
-  // eslint-disable-next-line no-unused-vars
+  /* eslint-disable no-unused-vars */
   flushPassiveEffects,
+  ReactActingRendererSigil,
+  /* eslint-enable no-unused-vars */
 ] = ReactDOM.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED.Events;
 
 function Event(suffix) {}

packages/react-dom/src/test-utils/ReactTestUtilsAct.js

@@ -33,11 +33,12 @@ const [
   runEventsInBatch,
   /* eslint-enable no-unused-vars */
   flushPassiveEffects,
+  ReactActingRendererSigil,
 ] = ReactDOM.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED.Events;
 
 const batchedUpdates = ReactDOM.unstable_batchedUpdates;
 
-const {ReactActingRendererSigil} = ReactSharedInternals;
+const {ReactCurrentActingRendererSigil} = ReactSharedInternals;
 
 // this implementation should be exactly the same in
 // ReactTestUtilsAct.js, ReactTestRendererAct.js, createReactNoop.js
@@ -87,17 +88,15 @@ function act(callback: () => Thenable) {
   let previousActingUpdatesScopeDepth = actingUpdatesScopeDepth;
   let previousActingUpdatesSigil;
   actingUpdatesScopeDepth++;
-  // we use the function flushPassiveEffects directly as the sigil,
-  // since it's unique to a renderer
   if (__DEV__) {
-    previousActingUpdatesSigil = ReactActingRendererSigil.current;
-    ReactActingRendererSigil.current = flushPassiveEffects;
+    previousActingUpdatesSigil = ReactCurrentActingRendererSigil.current;
+    ReactCurrentActingRendererSigil.current = ReactActingRendererSigil;
   }
 
   function onDone() {
     actingUpdatesScopeDepth--;
     if (__DEV__) {
-      ReactActingRendererSigil.current = previousActingUpdatesSigil;
+      ReactCurrentActingRendererSigil.current = previousActingUpdatesSigil;
       if (actingUpdatesScopeDepth > previousActingUpdatesScopeDepth) {
         // if it's _less than_ previousActingUpdatesScopeDepth, then we can assume the 'other' one has warned
         warningWithoutStack(

packages/react-noop-renderer/src/createReactNoop.js

@@ -81,7 +81,7 @@ type TextInstance = {|
 |};
 type HostContext = Object;
 
-const {ReactActingRendererSigil} = ReactSharedInternals;
+const {ReactCurrentActingRendererSigil} = ReactSharedInternals;
 
 const NO_CONTEXT = {};
 const UPPERCASE_CONTEXT = {};
@@ -650,7 +650,11 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
   const roots = new Map();
   const DEFAULT_ROOT_ID = '<default>';
 
-  const {flushPassiveEffects, batchedUpdates} = NoopRenderer;
+  const {
+    flushPassiveEffects,
+    batchedUpdates,
+    ReactActingRendererSigil,
+  } = NoopRenderer;
 
   // this act() implementation should be exactly the same in
   // ReactTestUtilsAct.js, ReactTestRendererAct.js, createReactNoop.js
@@ -700,17 +704,15 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     let previousActingUpdatesScopeDepth = actingUpdatesScopeDepth;
     let previousActingUpdatesSigil;
     actingUpdatesScopeDepth++;
-    // we use the function flushPassiveEffects directly as the sigil,
-    // since it's unique to a renderer
     if (__DEV__) {
-      previousActingUpdatesSigil = ReactActingRendererSigil.current;
-      ReactActingRendererSigil.current = flushPassiveEffects;
+      previousActingUpdatesSigil = ReactCurrentActingRendererSigil.current;
+      ReactCurrentActingRendererSigil.current = ReactActingRendererSigil;
     }
 
     function onDone() {
       actingUpdatesScopeDepth--;
       if (__DEV__) {
-        ReactActingRendererSigil.current = previousActingUpdatesSigil;
+        ReactCurrentActingRendererSigil.current = previousActingUpdatesSigil;
         if (actingUpdatesScopeDepth > previousActingUpdatesScopeDepth) {
           // if it's _less than_ previousActingUpdatesScopeDepth, then we can assume the 'other' one has warned
           warningWithoutStack(

packages/react-reconciler/src/ReactFiberReconciler.js

@@ -57,6 +57,7 @@ import {
   flushDiscreteUpdates,
   flushPassiveEffects,
   warnIfNotScopedWithMatchingAct,
+  ReactActingRendererSigil,
 } from './ReactFiberWorkLoop';
 import {createUpdate, enqueueUpdate} from './ReactUpdateQueue';
 import ReactFiberInstrumentation from './ReactFiberInstrumentation';
@@ -339,6 +340,7 @@ export {
   flushControlled,
   flushSync,
   flushPassiveEffects,
+  ReactActingRendererSigil,
 };
 
 export function getPublicRootInstance(

packages/react-reconciler/src/ReactFiberWorkLoop.js

@@ -173,7 +173,7 @@ const ceil = Math.ceil;
 const {
   ReactCurrentDispatcher,
   ReactCurrentOwner,
-  ReactActingRendererSigil,
+  ReactCurrentActingRendererSigil,
 } = ReactSharedInternals;
 
 type WorkPhase = 0 | 1 | 2 | 3 | 4 | 5 | 6;
@@ -2276,13 +2276,19 @@ function warnAboutInvalidUpdatesOnClassComponentsInDEV(fiber) {
   }
 }
 
+// We export a simple object here to be used by a renderer/test-utils
+// as the value of ReactCurrentActingRendererSigil.current
+// This identity lets us identify (ha!) when the wrong renderer's act()
+// wraps anothers' updates/effects
+export const ReactActingRendererSigil = {};
+
 export function warnIfNotScopedWithMatchingAct(fiber: Fiber): void {
   if (__DEV__) {
     if (
-      ReactActingRendererSigil.current !== null &&
+      ReactCurrentActingRendererSigil.current !== null &&
       // use the function flushPassiveEffects directly as the sigil
       // so this comparison is expected here
-      ReactActingRendererSigil.current !== flushPassiveEffects
+      ReactCurrentActingRendererSigil.current !== ReactActingRendererSigil
     ) {
       // it looks like we're using the wrong matching act(), so log a warning
       warningWithoutStack(
@@ -2309,7 +2315,7 @@ function warnIfNotCurrentlyActingUpdatesInDEV(fiber: Fiber): void {
   if (__DEV__) {
     if (
       workPhase === NotWorking &&
-      ReactActingRendererSigil.current !== flushPassiveEffects
+      ReactCurrentActingRendererSigil.current !== ReactActingRendererSigil
     ) {
       warningWithoutStack(
         false,

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

@@ -11,14 +11,15 @@ import type {Thenable} from 'react-reconciler/src/ReactFiberWorkLoop';
 import {
   batchedUpdates,
   flushPassiveEffects,
+  ReactActingRendererSigil,
 } from 'react-reconciler/inline.test';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 import warningWithoutStack from 'shared/warningWithoutStack';
 import {warnAboutMissingMockScheduler} from 'shared/ReactFeatureFlags';
 import enqueueTask from 'shared/enqueueTask';
 import * as Scheduler from 'scheduler';
 
-const {ReactActingRendererSigil} = ReactSharedInternals;
+const {ReactCurrentActingRendererSigil} = ReactSharedInternals;
 
 // this implementation should be exactly the same in
 // ReactTestUtilsAct.js, ReactTestRendererAct.js, createReactNoop.js
@@ -68,17 +69,15 @@ function act(callback: () => Thenable) {
   let previousActingUpdatesScopeDepth = actingUpdatesScopeDepth;
   let previousActingUpdatesSigil;
   actingUpdatesScopeDepth++;
-  // we use the function flushPassiveEffects directly as the sigil,
-  // since it's unique to a renderer
   if (__DEV__) {
-    previousActingUpdatesSigil = ReactActingRendererSigil.current;
-    ReactActingRendererSigil.current = flushPassiveEffects;
+    previousActingUpdatesSigil = ReactCurrentActingRendererSigil.current;
+    ReactCurrentActingRendererSigil.current = ReactActingRendererSigil;
   }
 
   function onDone() {
     actingUpdatesScopeDepth--;
     if (__DEV__) {
-      ReactActingRendererSigil.current = previousActingUpdatesSigil;
+      ReactCurrentActingRendererSigil.current = previousActingUpdatesSigil;
       if (actingUpdatesScopeDepth > previousActingUpdatesScopeDepth) {
         // if it's _less than_ previousActingUpdatesScopeDepth, then we can assume the 'other' one has warned
         warningWithoutStack(

packages/react/src/ReactActingRendererSigil.js → packages/react/src/ReactCurrentActingRendererSigil.js

@@ -13,7 +13,7 @@
  * so we can track identity of the renderer.
  */
 
-const ReactActingRendererSigil = {
+const ReactCurrentActingRendererSigil = {
   current: (null: null | (() => boolean)),
 };
-export default ReactActingRendererSigil;
+export default ReactCurrentActingRendererSigil;

packages/react/src/ReactSharedInternals.js

@@ -10,13 +10,13 @@ import ReactCurrentDispatcher from './ReactCurrentDispatcher';
 import ReactCurrentBatchConfig from './ReactCurrentBatchConfig';
 import ReactCurrentOwner from './ReactCurrentOwner';
 import ReactDebugCurrentFrame from './ReactDebugCurrentFrame';
-import ReactActingRendererSigil from './ReactActingRendererSigil';
+import ReactCurrentActingRendererSigil from './ReactCurrentActingRendererSigil';
 
 const ReactSharedInternals = {
   ReactCurrentDispatcher,
   ReactCurrentBatchConfig,
   ReactCurrentOwner,
-  ReactActingRendererSigil,
+  ReactCurrentActingRendererSigil,
   // Used by renderers to avoid bundling object-assign twice in UMD bundles:
   assign,
 };