Make cleanup function optional

Author: sebmarkbage

packages/react-art/src/ReactART.js

@@ -27,7 +27,6 @@ import {TYPES, childrenAsString} from './ReactARTInternals';
 
 function defaultOnDefaultTransitionIndicator() {
   // Noop
-  return function () {};
 }
 
 Mode.setCurrent(

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

@@ -46,7 +46,7 @@ export type CreateRootOptions = {
     error: mixed,
     errorInfo: {+componentStack?: ?string},
   ) => void,
-  onDefaultTransitionIndicator?: () => () => void,
+  onDefaultTransitionIndicator?: () => void | (() => void),
 };
 
 export type HydrateRootOptions = {
@@ -72,7 +72,7 @@ export type HydrateRootOptions = {
     error: mixed,
     errorInfo: {+componentStack?: ?string},
   ) => void,
-  onDefaultTransitionIndicator?: () => () => void,
+  onDefaultTransitionIndicator?: () => void | (() => void),
   formState?: ReactFormState<any, any> | null,
 };
 
@@ -97,7 +97,7 @@ import {
 } from 'react-reconciler/src/ReactFiberReconciler';
 import {ConcurrentRoot} from 'react-reconciler/src/ReactRootTags';
 
-function defaultOnDefaultTransitionIndicator() {
+function defaultOnDefaultTransitionIndicator(): void | (() => void) {
   // TODO: Implement the default
   return function () {};
 }

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

@@ -98,9 +98,8 @@ function nativeOnCaughtError(
 
   defaultOnCaughtError(error, errorInfo);
 }
-function nativeOnDefaultTransitionIndicator() {
+function nativeOnDefaultTransitionIndicator(): void | (() => void) {
   // Native doesn't have a default indicator.
-  return function () {};
 }
 
 function render(

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

@@ -113,9 +113,8 @@ function nativeOnCaughtError(
 
   defaultOnCaughtError(error, errorInfo);
 }
-function nativeOnDefaultTransitionIndicator() {
+function nativeOnDefaultTransitionIndicator(): void | (() => void) {
   // Native doesn't have a default indicator.
-  return function () {};
 }
 
 function render(

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

@@ -80,7 +80,7 @@ type CreateRootOptions = {
   unstable_transitionCallbacks?: TransitionTracingCallbacks,
   onUncaughtError?: (error: mixed, errorInfo: {componentStack: string}) => void,
   onCaughtError?: (error: mixed, errorInfo: {componentStack: string}) => void,
-  onDefaultTransitionIndicator?: () => () => void,
+  onDefaultTransitionIndicator?: () => void | (() => void),
   ...
 };
 type InstanceMeasurement = null;
@@ -1142,9 +1142,8 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     // TODO: Turn this on once tests are fixed
     // console.error(error);
   }
-  function onDefaultTransitionIndicator() {
+  function onDefaultTransitionIndicator(): void | (() => void) {
     // TODO: Allow this as an option.
-    return function () {};
   }
 
   let idCounter = 0;

packages/react-reconciler/src/ReactFiberReconciler.js

@@ -254,7 +254,7 @@ export function createContainer(
     error: mixed,
     errorInfo: {+componentStack?: ?string},
   ) => void,
-  onDefaultTransitionIndicator: () => () => void,
+  onDefaultTransitionIndicator: () => void | (() => void),
   transitionCallbacks: null | TransitionTracingCallbacks,
 ): OpaqueRoot {
   const hydrate = false;
@@ -302,7 +302,7 @@ export function createHydrationContainer(
     error: mixed,
     errorInfo: {+componentStack?: ?string},
   ) => void,
-  onDefaultTransitionIndicator: () => () => void,
+  onDefaultTransitionIndicator: () => void | (() => void),
   transitionCallbacks: null | TransitionTracingCallbacks,
   formState: ReactFormState<any, any> | null,
 ): OpaqueRoot {

packages/react-reconciler/src/ReactFiberRoot.js

@@ -179,7 +179,7 @@ export function createFiberRoot(
     error: mixed,
     errorInfo: {+componentStack?: ?string},
   ) => void,
-  onDefaultTransitionIndicator: () => () => void,
+  onDefaultTransitionIndicator: () => void | (() => void),
   transitionCallbacks: null | TransitionTracingCallbacks,
 ): FiberRoot {
   // $FlowFixMe[invalid-constructor] Flow no longer supports calling new on functions

packages/react-reconciler/src/ReactInternalTypes.js

@@ -280,7 +280,7 @@ type BaseFiberRootProperties = {
     errorInfo: {+componentStack?: ?string},
   ) => void,
 
-  onDefaultTransitionIndicator: () => () => void,
+  onDefaultTransitionIndicator: () => void | (() => void),
 
   formState: ReactFormState<any, any> | null,
 

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

@@ -60,9 +60,8 @@ import {
   disableLegacyMode,
 } from 'shared/ReactFeatureFlags';
 
-function defaultOnDefaultTransitionIndicator() {
+function defaultOnDefaultTransitionIndicator(): void | (() => void) {
   // Noop
-  return function () {};
 }
 
 // $FlowFixMe[prop-missing]: This is only in the development export.