Setting subfield-level errors from an array field's validator?

[adamkangas]

I'm aware that we can return field-level errors from validators on our FormApi – but I was wondering what thoughts were on returning subfield-level errors on a FieldApi's validators when mode="array" is set.

In my case, users are building a list of proposed room bookings and we need to validate the entire proposed array simultaneously whenever it changes – looking for conflicts with existing bookings in the database, but also ensuring that the proposals don't conflict with themselves.

It would be handy to add an onChangeAsync to proposedBookings that can directly set multiple subfield errors like proposedBookings[0].startDatetime and proposedBookings[2].venue

Again, I know I can handle this at the form level, but this form is quite complex and I'd prefer not to fire off async requests when unrelated fields are changed. Any other approaches that might be recommended?