_serial_from_unique_id took the entry's unique_id at face value. That is
right for an entry whose unique_id holds a real serial, but the unique_id
records what the config flow believed when it ran, not what the registry
holds now -- and for two firmware families those are different things.
Entries added before the placeholder rules landed (issues #83/#189) were
keyed on the placeholder itself: `localthings_Nothing(SVC)` for the
ARTIK051_DONGLE_REF dongles, `localthings_FFFFFFFFFFFFFFF` for the
DA_WM_A51_20_COMMON laundry boards. The coordinator has been resolving
those same boards to the host ever since, so their devices and entities
are host-keyed today. Migration read the placeholder back off the
unique_id, decided the host-keyed rows were the stale ones, and rewrote
them onto the placeholder -- reintroducing exactly the collision those
issues exist to prevent, since every unit of the family reports the same
placeholder and would go back to sharing entity unique_ids.
Run the recovered string through resolve_serial, which is the whole point
of that helper being shared. The old `host:port` special case stays: it's
a config-flow-history artifact rather than a device-reported serial, so
resolve_serial can't recognize it.
The repair pass had a second, narrower way to lose data. Removing a device
takes its entities with it (entity_registry.async_device_modified), and
the removal branch ran after the entity pass -- so an entity that had just
been re-keyed rather than removed, because its serial-keyed key was free,
was destroyed a few lines later along with the entity_id, name and area
the rewrite existed to preserve. Move surviving entities onto the device
they now belong to before removing the duplicate.
Reachable when the serial-keyed device exists but a given entity's
serial-keyed key doesn't -- e.g. the user deleted the visible duplicate by
hand, which is the first thing anyone hitting #236 tries.
Also fold the modelNum `<model>|<board>` split into resolve_model beside
resolve_serial. The config flow and _run_discovery each had their own copy
under a comment promising they matched; a device that renames itself on
the first poll is what a drift there looks like.
Marc Billow
b5699badbe