[v4] Fallback to full reload if React version doesn't support Fast Refresh

[n3tr]

Changes

Fallback to the full reload if React version doesn't support Fast Refresh

• Overwrite FAST_REFRESH to false if the current react version doesn't support (< 16.10.0)
• Remove Fast Refresh warning on the older react version since we will automatically fallback to do full reload.

Verify steps

Default setup

• yarn create-react-app my-app
• yarn start
• Modify App.js content
• The app gets updated through Fast Refresh

FAST_REFRESH=false

• Start the app by using FAST_REFRESH=false yarn start
• Modify App.js
• The app should do a full reload

React version that Fast Refresh is unavailable (e.g. 15)

• Change React version to 15.7.0
  • yarn add [email protected] [email protected]
  • Remove <React.StrictMode> from index.js
• yarn start and
• Modify App.js
• The app should do a full reload

[ianschmitz]

We took a different approach in #9861 by attempting to import react/jsx-runtime as recommended by the React team. They have back-ported support to a number of major releases.

Thanks for the PR!

[kokolay410]

#9918

[n3tr]

@ianschmitz I think this one is different from #9861, as I understand, #9861 is about jsx-runtime.

This is more about detecting if the React version supports Fast Refresh or not, otherwise, it will fall back to full reload.

[ianschmitz]

Ah, apologies I confused the two.

[n3tr]

@ianschmitz Dun worry! 😄 Should I create another PR for this or just leave it here?

[n3tr]

@ianschmitz

I moved to #9971 since this has duplicated fixes with others, and I have messed up this branch.