If there is a retail building in OSM which only contains one shop in it that is marked as a store node, should I add the full address to both the building and the store node, or just the store node?
In some cases shop has own address: sometimes business within building has a distinct house number or you can tag addr:unit number/code.
In case when shop has the same address as building - adding address detail to it is not needed. But it is also not really harmful.
Ideally data consumers would be able to derive such addres from being within building with address, but many tools cannot do this. Note that in one case, building would need to derive its address from freefloating housenumber node, then POIs would need to be linked with building.
Though note that moving address from building or separate node to shop and deleting source is unhelpful and should be avoided.
I prefer both entries. The router finds the shop via house, but applications that display shops (e.g. Openstreetbrowser) do not show the house with address when searching for a specific shop, but only the details of the shop.
As a searcher, I want to know everything… 