`useConfirm` calls deprecated `ReactDOM.render`, triggering warning in React 18

[iansan5653]

useConfirm uses ReactDOM.render to inject the confirmation dialog into the HTML.

react/src/Dialog/ConfirmationDialog.tsx

Lines 161 to 168 in 72f0ec6

	ReactDOM.render(
	<ThemeProvider {...themeProps}>
	<ConfirmationDialog {...confirmationDialogProps} onClose={onClose}>
	{content}
	</ConfirmationDialog>
	</ThemeProvider>,
	hostElement,
	)

This triggers a warning in the console when in development mode:

Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot

While the warning states that the whole app will behave like it's running React 17, this isn't really the case - only the dialog will. This is because the call to render creates a whole new React app instance which only contains the dialog. However, this still isn't great and we definitely should resolve this.

---

The obvious solution is to just use createRoot instead, but it seems like there must be a more elegant alternative here than to create an entirely new React application. What if we could come up with a way to extract the Portal component into a usePortal hook, allowing rendering arbitary JSX into the default portal from any hook? Something like this:

function useConfirm() {
  const renderIntoPortal = usePortal()

  return () => new Promise(_resolve => {
    const resolve = (result) => {
      _resolve(result)
      renderIntoPortal(null)
    }
    renderIntoPortal(
      <ConfirmationDialog onClose={resolve(false)}>
        <Button onClick={resolve(true)}>Confirm</Button>
      </ConfirmationDialog>
    )
  })
}

I'm not sure if this is actually technically possible though - maybe I'll try and come up with a POC this week.

[mattcosta7]

One thing that might cause some interesting changes/need consideration

Synthetic Events are bound to the parent react root, so events from a portal'd element will bubble the react dom, where calling render like the confirm does now creates a new react root that events shouldn't (iirc) bubble the react root from (but can bubble the dom).

we would likely need a portal that blocks events from bubbling the react root in that case (which maybe portals should always optionally do)

[radglob]

Closed by #3367