Closes https://github.com/microsoft/playwright/issues/32853
Vite turns the shorthand fragment notation `<></>` into `import {
Fragment } from "react"; <Fragment></Fragment>`. On the Node.js side of
things, this `react` import resolves to our mock version of React, which
currently mocks `Fragment` as `{}`. Currently, we pass that straight to
`React.createElement`, which throws an error.
The fix is to make our `Fragment` mock detectable with a tag, and when
we render it replace it with the real `__pwReact.Fragment`.
What was happening?
- When we use CT, we go over the test files, look at the imports using
`tsxTransform.ts` and store them inside a map, these we feed into the
import registry which we build using Vite and have access inside the
browser
- In case of an inline component in the same file as where the test file
is, this is not happening.
- jsx-runtime via babel kicks in, transforms every JSX component in
something like that:
```
{
__pw_type: 'jsx',
type: [Function: MyInlineComponent],
props: { value: 'Max' },
key: undefined
}
```
this then gets passed into `wrapObject` which maps any function from the
Node.js side into expose function calls so they work inside the browser.
The assumption for `wrapObject` was to do it mostly for callbacks. So it
does for `type` - which is actually our component. We then pass this to
the React render function, which calls back the exposed function but we
never return anything, so it mounts `undefined`.
---
While there have been experiments from certain vendors to get the
'client only' code inside a server side file, we should throw for now to
not confuse users. We might revisit this in the future since Babel / TSX
doesn't support it outside of the box.
Fixes https://github.com/microsoft/playwright/issues/32167
