Switch to IS_REACT_ACT_ENVIRONMENT instead of act when needed when using react 18

src/__tests__/waitFor.test.tsx

@@ -1,5 +1,5 @@
 import * as React from 'react';
-import { Text, TouchableOpacity, View } from 'react-native';
+import { Text, TouchableOpacity, View, Pressable } from 'react-native';
 import { fireEvent, render, waitFor } from '..';
 
 class Banana extends React.Component<any> {
@@ -78,6 +78,40 @@ test('waits for element with custom interval', async () => {
   expect(mockFn).toHaveBeenCalledTimes(2);
 });
 
+// this component is convoluted on purpose. It is not a good react pattern, but it is valid
+// react code that will run differently between different react versions (17 and 18), so we need
+// explicit tests for it
+const Comp = ({ onPress }: { onPress: () => void }) => {
+  const [state, setState] = React.useState(false);
+
+  React.useEffect(() => {
+    if (state) {
+      onPress();
+    }
+  }, [state, onPress]);
+
+  return (
+    <Pressable
+      onPress={async () => {
+        await Promise.resolve();
+        setState(true);
+      }}
+    >
+      <Text>Trigger</Text>
+    </Pressable>
+  );
+};
+test('waits for async event with fireEvent', async () => {
+  const spy = jest.fn();
+  const { getByText } = render(<Comp onPress={spy} />);
+
+  fireEvent.press(getByText('Trigger'));
+
+  await waitFor(() => {
+    expect(spy).toHaveBeenCalled();
+  });
+});
+
 test.each([false, true])(
   'waits for element until it stops throwing using fake timers (legacyFakeTimers = %s)',
   async (legacyFakeTimers) => {

src/act.ts

@@ -1,7 +1,95 @@
-import { act } from 'react-test-renderer';
+// This file and the act() implementation is sourced from react-testing-library
+// https://github.com/testing-library/react-testing-library/blob/c80809a956b0b9f3289c4a6fa8b5e8cc72d6ef6d/src/act-compat.js
+import { act as reactTestRendererAct } from 'react-test-renderer';
+import { checkReactVersionAtLeast } from './react-versions';
 
 const actMock = (callback: () => void) => {
   callback();
 };
 
-export default act || actMock;
+// See https://github.com/reactwg/react-18/discussions/102 for more context on global.IS_REACT_ACT_ENVIRONMENT
+declare global {
+  var IS_REACT_ACT_ENVIRONMENT: boolean | undefined;
+}
+
+function setIsReactActEnvironment(isReactActEnvironment: boolean | undefined) {
+  globalThis.IS_REACT_ACT_ENVIRONMENT = isReactActEnvironment;
+}
+
+function getIsReactActEnvironment() {
+  return globalThis.IS_REACT_ACT_ENVIRONMENT;
+}
+
+type Act = typeof reactTestRendererAct;
+
+function withGlobalActEnvironment(actImplementation: Act) {
+  return (callback: Parameters<Act>[0]) => {
+    const previousActEnvironment = getIsReactActEnvironment();
+    setIsReactActEnvironment(true);
+
+    // this code is riddled with eslint disabling comments because this doesn't use real promises but eslint thinks we do
+    try {
+      // The return value of `act` is always a thenable.
+      let callbackNeedsToBeAwaited = false;
+      const actResult = actImplementation(() => {
+        const result = callback();
+        if (
+          result !== null &&
+          typeof result === 'object' &&
+          // @ts-expect-error this should be a promise or thenable
+          // eslint-disable-next-line promise/prefer-await-to-then
+          typeof result.then === 'function'
+        ) {
+          callbackNeedsToBeAwaited = true;
+        }
+        return result;
+      });
+      if (callbackNeedsToBeAwaited) {
+        const thenable = actResult;
+        return {
+          then: (
+            resolve: (value: never) => never,
+            reject: (value: never) => never
+          ) => {
+            // eslint-disable-next-line
+            thenable.then(
+              // eslint-disable-next-line promise/always-return
+              (returnValue) => {
+                setIsReactActEnvironment(previousActEnvironment);
+                resolve(returnValue);
+              },
+              (error) => {
+                setIsReactActEnvironment(previousActEnvironment);
+                reject(error);
+              }
+            );
+          },
+        };
+      } else {
+        setIsReactActEnvironment(previousActEnvironment);
+        return actResult;
+      }
+    } catch (error) {
+      // Can't be a `finally {}` block since we don't know if we have to immediately restore IS_REACT_ACT_ENVIRONMENT
+      // or if we have to await the callback first.
+      setIsReactActEnvironment(previousActEnvironment);
+      throw error;
+    }
+  };
+}
+const getAct = () => {
+  if (!reactTestRendererAct) {
+    return actMock;
+  }
+
+  return checkReactVersionAtLeast(18, 0)
+    ? withGlobalActEnvironment(reactTestRendererAct)
+    : reactTestRendererAct;
+};
+const act = getAct();
+
+export default act;
+export {
+  setIsReactActEnvironment as setReactActEnvironment,
+  getIsReactActEnvironment,
+};

src/index.ts

@@ -1,17 +1,33 @@
 import { cleanup } from './pure';
 import { flushMicroTasks } from './flushMicroTasks';
+import { getIsReactActEnvironment, setReactActEnvironment } from './act';
 
-// If we're running in a test runner that supports afterEach
-// then we'll automatically run cleanup afterEach test
-// this ensures that tests run in isolation from each other
-// if you don't like this then either import the `pure` module
-// or set the RNTL_SKIP_AUTO_CLEANUP env variable to 'true'.
-if (typeof afterEach === 'function' && !process.env.RNTL_SKIP_AUTO_CLEANUP) {
-  // eslint-disable-next-line no-undef
-  afterEach(async () => {
-    await flushMicroTasks();
-    cleanup();
-  });
+if (typeof process === 'undefined' || !process.env?.RNTL_SKIP_AUTO_CLEANUP) {
+  // If we're running in a test runner that supports afterEach
+  // then we'll automatically run cleanup afterEach test
+  // this ensures that tests run in isolation from each other
+  // if you don't like this then either import the `pure` module
+  // or set the RNTL_SKIP_AUTO_CLEANUP env variable to 'true'.
+  if (typeof afterEach === 'function') {
+    // eslint-disable-next-line no-undef
+    afterEach(async () => {
+      await flushMicroTasks();
+      cleanup();
+    });
+  }
+
+  if (typeof beforeAll === 'function' && typeof afterAll === 'function') {
+    // This matches the behavior of React < 18.
+    let previousIsReactActEnvironment = getIsReactActEnvironment();
+    beforeAll(() => {
+      previousIsReactActEnvironment = getIsReactActEnvironment();
+      setReactActEnvironment(true);
+    });
+
+    afterAll(() => {
+      setReactActEnvironment(previousIsReactActEnvironment);
+    });
+  }
 }
 
 export * from './pure';

src/react-versions.ts

@@ -0,0 +1,11 @@
+import * as React from 'react';
+
+export function checkReactVersionAtLeast(
+  major: number,
+  minor: number
+): boolean {
+  if (React.version === undefined) return false;
+  const [actualMajor, actualMinor] = React.version.split('.').map(Number);
+
+  return actualMajor > major || (actualMajor === major && actualMinor >= minor);
+}

src/waitFor.ts

@@ -1,24 +1,17 @@
 /* globals jest */
-import * as React from 'react';
-import act from './act';
+import act, { setReactActEnvironment, getIsReactActEnvironment } from './act';
 import { ErrorWithStack, copyStackTrace } from './helpers/errors';
 import {
   setTimeout,
   clearTimeout,
   setImmediate,
   jestFakeTimersAreEnabled,
 } from './helpers/timers';
+import { checkReactVersionAtLeast } from './react-versions';
 
 const DEFAULT_TIMEOUT = 1000;
 const DEFAULT_INTERVAL = 50;
 
-function checkReactVersionAtLeast(major: number, minor: number): boolean {
-  if (React.version === undefined) return false;
-  const [actualMajor, actualMinor] = React.version.split('.').map(Number);
-
-  return actualMajor > major || (actualMajor === major && actualMinor >= minor);
-}
-
 export type WaitForOptions = {
   timeout?: number;
   interval?: number;
@@ -194,6 +187,17 @@ export default async function waitFor<T>(
   const stackTraceError = new ErrorWithStack('STACK_TRACE_ERROR', waitFor);
   const optionsWithStackTrace = { stackTraceError, ...options };
 
+  if (checkReactVersionAtLeast(18, 0)) {
+    const previousActEnvironment = getIsReactActEnvironment();
+    setReactActEnvironment(false);
+
+    try {
+      return await waitForInternal(expectation, optionsWithStackTrace);
+    } finally {
+      setReactActEnvironment(previousActEnvironment);
+    }
+  }
+
   if (!checkReactVersionAtLeast(16, 9)) {
     return waitForInternal(expectation, optionsWithStackTrace);
   }