The spec's sixth question is skipped when the account already carries the
preferences, and the flow had no way to know: `User.unitPreference` is
nullable with null meaning "default metric", and the account payload coerces
that away, so nothing downstream could tell a chosen metric from an unset
column. The two columns are read raw on the server now, into the same
vocabulary the wire publishes, and a record whose account holds both reads its
`units` step as done — the question answers itself and is never put again.
Read-side only: the stored ledger keeps saying pending, because the person
really has not answered it, and an answer given later still lands.
The two writes the units answer makes — the display columns and the record of
the answer — go in one transaction, so a failure between them can no longer
leave the columns changed with no record of what changed them.
Marc-André Bombeck
7a1f3fe32d