That's with

@dataclass(frozen=True)
class JavaTestFieldSet(TestFieldSet):
    required_fields = (JavaTestsSources,)

    sources: JavaTestsSources

Are you using from __future import annotations in your implementation? That breaks FieldSets 🤦‍♂️ Sorry for the gotcha

Oh yup. For which module? Just where I define the FieldSet?

You can and should use it everywhere except for files that define FieldSets (And I should fix this)

(Looks like yeah, just the FieldSet)