[v4] Bug: React 17, React is not defined after ejecting

[alpeer]

React version: 17.0.1

Steps To Reproduce

1. npx create-react-app my-app
2. cd my-app
3. npm start (Works like a charm)
4. npm run eject
5. npm i
6. npm start (ReferenceError: React is not defined)

Link to code example: https://codesandbox.io/s/ecstatic-wood-ou6px

The current behavior

I upgraded react to 17 and removed "import React"s from my project files (except index.js where react mounted). But I got "ReferenceError: React is not defined" in those files.
To investigate the issue behind this, I created a new react app, the new JSX transformation was working. But when I eject, it throws the same errors.
So;
Without react-scripts, new JSX transformation doesn't working.

The expected behavior

Components should render without declaring React (import React from "react") if React is in scope.

[kachkaev]

I guess that this issue should be moved to https://github.com/facebook/create-react-app

[alpeer]

This is not an issue about create-react-app.
I don't use create-react-app in the project I had problem with jsx-transformation.
I have just mention to show you example and give more idea about issue.

Thanks for replying quickly.
Happy coding :)

[mordechaim]

I'm having this exact issue even without ejecting. I followed the migration guide, ran react-codemod, deleted node_modules.

The compiler says the code compiled successfully but getting the red screen in the browser.

[n3tr]

@alpeer

Upgrade React 17 and remove import React statements won't work since React doesn't do any JSX transform, you need babel plugin for that (https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html#manual-babel-setup).

---

the CRA ejection issue has been fixed in #9885 and needs to wait for the maintainer to publish a new version.

:)