Trying to detect host component names triggered the following error (Expected "}" but found "$NonMaybeType")

[natew]

Describe the bug

Getting this error after upgrading to Expo 52:

Expected behavior

No bug

Steps to Reproduce

Sorry to half-fill this in, was wondering if anyone had any idea how this occurs or any fixes? I can't find anything on google or in the repo, seems like it's somehow hitting flow syntax unexpectedly.

[mdjastrzebski]

Hi @natew, I've tested RNTL 12.x (latest stable) on Expo 52 not long ago in #1689 and all tests in our example apps passed correctly.

The error you have received seems pretty odd, it looks like some Flow processing error ($NonMaybeType) happening when detectHostComponentNames is called in render. This seems a bit unusual, as I would expect such errors to happen before any test execution as Node (Jest) parses all of the imports. This seems to indicate some dynamic import is happening. There is also a Proxy.render in your stack trace.

Are you using normal Expo + Jest setup? Could you provide minimal repro?

Also worth noting is that the RNTL 13, now in RC, drops detectHostComponentNames usage, so you can check if this error occurs also against it.