[Bug]: Fetchers have no data in remix test with yarn pnp

[alisd23]

What version of React Router are you using?

6.27.0

Steps to Reproduce

See reproduction + Readme here: https://codesandbox.io/p/devbox/5xv9jn?file=%2FREADME.md%3A25%2C37

I have set up a very simple test case to show the fetcher data being wrong. This seems like a test-only issue as I discovered it while using createRemixStub, and I haven't seen a similar issue before in my actual app.

I wasn't sure whether to file this in the react-router or remix repository, but I think the core issue is here in react-router, even though the reproduction uses Remix.

Follow instructions to simply flip between pnp (failing) and non-pnp (passing) mode.

Expected Behavior

The fetcher returned from useFetcher should include a data value of { result: 100 }, as returned from the action.

Actual Behavior

The data property from useFetcher() stays undefined, even after the action successfully returns.

Interestingly the fetcher details returned from useFetchers() (plural) does show the resolved action data - which is very strange.

Took a bit of a look but the RR code is fairly complex. There is a suspicious looking fetcherData ref, which is passed down to in a context provider value as fetcherData.current, which could maybe be a source of pain (as changing a ref value won't automatically trigger re-render). But that's just a hunch.