do not save names when falling back to addresses

If an object doesn't have a useable main tag, then the names should
always be ignored, independently of the presence of housenumbers.
We have to assume that the name belongs to a feature that was
intentionally filtered out.

lib-lua/themes/nominatim/init.lua

@@ -134,6 +134,22 @@ function PlaceTransform.named_with_key(place, k)
     end
 end
 
+-- Special transform used with address fallbacks: ignore all names
+-- except for those marked as being part of the address.
+local function address_fallback(place)
+    if next(place.names) == nil or NAMES.house == nil then
+        return place
+    end
+
+    local names = {}
+    for k, v in pairs(place.names) do
+        if NAME_FILTER(k, v) == 'house' then
+            names[k] = v
+        end
+    end
+    return place:clone{names=names}
+end
+
 --------- Built-in extratags transformation functions ---------------
 
 local function default_extratags_filter(p, k)
@@ -379,7 +395,7 @@ function Place:grab_name_parts(data)
                     self.has_name = true
                 elseif atype == 'house' then
                     self.has_name = true
-                    fallback = {'place', 'house', PlaceTransform.always}
+                    fallback = {'place', 'house', address_fallback}
                 end
             end
         end
@@ -636,7 +652,7 @@ function module.process_tags(o)
 
     -- address keys
     if o:grab_address_parts{groups=ADDRESS_FILTER} > 0 and fallback == nil then
-        fallback = {'place', 'house', PlaceTransform.always}
+        fallback = {'place', 'house', address_fallback}
     end
     if o.address.country ~= nil and #o.address.country ~= 2 then
         o.address['country'] = nil

settings/address-levels.json

@@ -74,6 +74,14 @@
           "stone" : 30,
           "" : [22, 0]
       },
+      "water" : {
+          "lake" : [20, 0],
+          "reservoir" : [20, 0],
+          "wastewater" : [24, 0],
+          "pond" : [24, 0],
+          "fountain" : [24, 0],
+          "" : [22, 0]
+      },
       "waterway" : {
           "river" : [19, 0],
           "stream" : [22, 0],

test/bdd/api/search/queries.feature

@@ -192,7 +192,7 @@ Feature: Search queries
         Then exactly 1 result is returned
         And results contain
           | class   |
-          | natural |
+          | water |
 
     Examples:
       | data |

test/bdd/osm2pgsql/import/tags.feature

@@ -256,3 +256,16 @@ Feature: Tag evaluation
             | N21:natural | water |
             | N23:water   | pond  |
             | N26:natural | water |
+
+    Scenario: Drop name for address fallback
+        When loading osm data
+            """
+            n1 Taddr:housenumber=23,name=Foo
+            n2 Taddr:housenumber=23,addr:housename=Foo
+            n3 Taddr:housenumber=23
+            """
+        Then place contains exactly
+            | object      | type  | address             | name |
+            | N1:place    | house | 'housenumber': '23' | -    |
+            | N2:place    | house | 'housenumber': '23' | 'addr:housename': 'Foo' |
+            | N3:place    | house | 'housenumber': '23' | -    |