serde(default) would actually be a footgun for us.

because it means json files with missing fields would potentially match multiple versions of the enum (since it'd just fallback to default).

setting a fixed version number ensured each file has an explicit non-ambiguous version number

This is what we went with, but the cherry on top was to be able to ensure versioning through type-safety (i.e.: prevent us from changing the struct and forgetting to update version number, which would break on user's side)

not quite all the way, but this helped a lot: github.com/ethui/ethui/...