feat: Add support for React 18 (#1031)

BREAKING CHANGE: Drop support for React 17 and earlier. We'll use the new [`createRoot` API](reactwg/react-18#5) by default which comes with a set of [changes while also enabling support for concurrent features](reactwg/react-18#4).
To can opt-out of this change by using `render(ui, { legacyRoot: true } )`. But be aware that the legacy root API is deprecated in React 18 and its usage will trigger console warnings.

Co-authored-by: Philipp Fritsche <[email protected]>

.github/workflows/validate.yml

@@ -16,6 +16,7 @@ jobs:
     # ignore all-contributors PRs
     if: ${{ !contains(github.head_ref, 'all-contributors') }}
     strategy:
+      fail-fast: false
       matrix:
         # TODO: relax `'16.9.1'` to `16` once GitHub has 16.9.1 cached. 16.9.0 is broken due to https://github.com/nodejs/node/issues/40030
         node: [12, 14, '16.9.1']
@@ -52,6 +53,8 @@ jobs:
 
       - name: ⬆️ Upload coverage report
         uses: codecov/codecov-action@v1
+        with:
+          flags: ${{ matrix.react }}
 
   release:
     needs: main

package.json

@@ -46,22 +46,22 @@
   "license": "MIT",
   "dependencies": {
     "@babel/runtime": "^7.12.5",
-    "@testing-library/dom": "^8.0.0",
+    "@testing-library/dom": "^8.5.0",
     "@types/react-dom": "*"
   },
   "devDependencies": {
     "@testing-library/jest-dom": "^5.11.6",
     "dotenv-cli": "^4.0.0",
     "kcd-scripts": "^11.1.0",
     "npm-run-all": "^4.1.5",
-    "react": "^17.0.1",
-    "react-dom": "^17.0.1",
+    "react": "^18.0.0",
+    "react-dom": "^18.0.0",
     "rimraf": "^3.0.2",
     "typescript": "^4.1.2"
   },
   "peerDependencies": {
-    "react": "*",
-    "react-dom": "*"
+    "react": "^18.0.0",
+    "react-dom": "^18.0.0"
   },
   "eslintConfig": {
     "extends": "./node_modules/kcd-scripts/eslint.js",

src/__tests__/act.js

@@ -1,5 +1,5 @@
 import * as React from 'react'
-import {render, fireEvent, screen} from '../'
+import {act, render, fireEvent, screen} from '../'
 
 test('render calls useEffect immediately', () => {
   const effectCb = jest.fn()
@@ -43,3 +43,27 @@ test('calls to hydrate will run useEffects', () => {
   render(<MyUselessComponent />, {hydrate: true})
   expect(effectCb).toHaveBeenCalledTimes(1)
 })
+
+test('cleans up IS_REACT_ACT_ENVIRONMENT if its callback throws', () => {
+  global.IS_REACT_ACT_ENVIRONMENT = false
+
+  expect(() =>
+    act(() => {
+      throw new Error('threw')
+    }),
+  ).toThrow('threw')
+
+  expect(global.IS_REACT_ACT_ENVIRONMENT).toEqual(false)
+})
+
+test('cleans up IS_REACT_ACT_ENVIRONMENT if its async callback throws', async () => {
+  global.IS_REACT_ACT_ENVIRONMENT = false
+
+  await expect(() =>
+    act(async () => {
+      throw new Error('thenable threw')
+    }),
+  ).rejects.toThrow('thenable threw')
+
+  expect(global.IS_REACT_ACT_ENVIRONMENT).toEqual(false)
+})

src/__tests__/cleanup.js

@@ -83,10 +83,7 @@ describe('fake timers and missing act warnings', () => {
     expect(microTaskSpy).toHaveBeenCalledTimes(0)
     // console.error is mocked
     // eslint-disable-next-line no-console
-    expect(console.error).toHaveBeenCalledTimes(
-      // ReactDOM.render is deprecated in React 18
-      React.version.startsWith('18') ? 1 : 0,
-    )
+    expect(console.error).toHaveBeenCalledTimes(0)
   })
 
   test('cleanup does not swallow missing act warnings', () => {
@@ -118,16 +115,10 @@ describe('fake timers and missing act warnings', () => {
     expect(deferredStateUpdateSpy).toHaveBeenCalledTimes(1)
     // console.error is mocked
     // eslint-disable-next-line no-console
-    expect(console.error).toHaveBeenCalledTimes(
-      // ReactDOM.render is deprecated in React 18
-      React.version.startsWith('18') ? 2 : 1,
-    )
+    expect(console.error).toHaveBeenCalledTimes(1)
     // eslint-disable-next-line no-console
-    expect(
-      console.error.mock.calls[
-        // ReactDOM.render is deprecated in React 18
-        React.version.startsWith('18') ? 1 : 0
-      ][0],
-    ).toMatch('a test was not wrapped in act(...)')
+    expect(console.error.mock.calls[0][0]).toMatch(
+      'a test was not wrapped in act(...)',
+    )
   })
 })

src/__tests__/new-act.js

@@ -1,4 +1,4 @@
-let asyncAct, consoleErrorMock
+let asyncAct
 
 jest.mock('react-dom/test-utils', () => ({
   act: cb => {
@@ -8,12 +8,12 @@ jest.mock('react-dom/test-utils', () => ({
 
 beforeEach(() => {
   jest.resetModules()
-  asyncAct = require('../act-compat').asyncAct
-  consoleErrorMock = jest.spyOn(console, 'error').mockImplementation(() => {})
+  asyncAct = require('../act-compat').default
+  jest.spyOn(console, 'error').mockImplementation(() => {})
 })
 
 afterEach(() => {
-  consoleErrorMock.mockRestore()
+  console.error.mockRestore()
 })
 
 test('async act works when it does not exist (older versions of react)', async () => {