The /meters reading for an engine event, or null for every other event — each of those
lands on its own row (publishEngineEventRow), and meters are the one periodic reading the
feed records whole. The switch stays exhaustive over EngineEvent deliberately: it is
the compile-time question every new engine event must answer — does this fact reach a client,
and through which door — and the answer is null for anything whose door is its own row.
The
/metersreading for an engine event, ornullfor every other event — each of those lands on its own row (publishEngineEventRow), and meters are the one periodic reading the feed records whole. The switch stays exhaustive over EngineEvent deliberately: it is the compile-time question every new engine event must answer — does this fact reach a client, and through which door — and the answer isnullfor anything whose door is its own row.