DevTools warning: SharedArrayBuffer will require cross-origin isolation

Describe the bug

When creating an app via npx create-react-app and running it, a warning pops up in DevTools (Chrome 88 and 89):

scheduler.development.js:298 [Deprecation] SharedArrayBuffer will require cross-origin isolation as of M91, around May 2021. See https://developer.chrome.com/blog/enabling-shared-array-buffer/ for more details.

Did you try recovering your dependencies?

Yes

Which terms did you search for in User Guide?

sharedarraybuffer returned no result.

Environment

  current version of create-react-app: 4.0.1
  running from /Users/maudn/.npm/_npx/25767/lib/node_modules/create-react-app
  Binaries:
    Node: 14.15.4 - ~/.nvm/versions/node/v14.15.4/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.10 - ~/.nvm/versions/node/v14.15.4/bin/npm
  Browsers:
    Chrome: 88.0.4324.96
    Edge: 87.0.664.66
    Firefox: 84.0
    Safari: 14.0.2
  npmPackages:
    react: ^17.0.1 => 17.0.1
    react-dom: ^17.0.1 => 17.0.1
    react-scripts: Not Found
  npmGlobalPackages:
    create-react-app: Not Found

Steps to reproduce

1. npx create-react-app myapp
2. cd myapp && npm start
3. Open http://localhost:3000 in Chrome 88 or 89, regular or Incognito mode
4. Open DevTools: the warning is displayed

Expected behavior

Actual behavior

Warning: scheduler.development.js:298 [Deprecation] SharedArrayBuffer will require cross-origin isolation as of M91, around May 2021. See https://developer.chrome.com/blog/enabling-shared-array-buffer/ for more details.

Reproducible demo

See instructions in Steps to reproduce. Thank you!

[waynebloss]

@sonpnh95 Perhaps some other package is using SharedArrayBuffer. For this reason and for people who didn’t upgrade yet to react v17 you can apply this workaround somewhere in your index.html file or elsewhere:

    <!-- Issue workaround for React v16. -->
    <script>
      // See https://github.com/facebook/react/issues/20829#issuecomment-802088260
      if (!crossOriginIsolated) SharedArrayBuffer = ArrayBuffer;
    </script>

[bvaughn]

The fix only landed a few days ago and has not yet been released.