Hm, that's an interesting workaround. It means that user can't create Product(name='Plasma Tv', price=999.98) manually. I'm not sure I understand all consequences. It seems we don't test init=False dataclasses in itemadapter (//cc @elacuesta), I'm not sure what's the behavior e.g. with serialization, if fields are missing.

Overall, this looks like an issue in itemloader which can be fixed, not a problem with dataclasses or itemadapter. Fixing it is out of scope for this PR though.

What do you think about asking to provide default field values instead, and saying "currently" when explaining this limitation? We may want to lift it in future.

Originally posted by @kmike in #13