look for extra place tags in Nominatim search results

Administrative boundaries at municipality level are generally
better described by the place node (as town, village etc.).
Nominatim exports the place type in extratags if it was able
to merge place nodes with admin boundaries. Use this preferably
to create the descriptive term.

app/controllers/geocoder_controller.rb

@@ -149,7 +149,7 @@ def search_osm_nominatim
     exclude = "&exclude_place_ids=#{params[:exclude]}" if params[:exclude]
 
     # ask nominatim
-    response = fetch_xml("http:#{NOMINATIM_URL}search?format=xml&q=#{escape_query(query)}#{viewbox}#{exclude}&accept-language=#{http_accept_language.user_preferred_languages.join(',')}")
+    response = fetch_xml("http:#{NOMINATIM_URL}search?format=xml&extratags=1&q=#{escape_query(query)}#{viewbox}#{exclude}&accept-language=#{http_accept_language.user_preferred_languages.join(',')}")
 
     # extract the results from the response
     results =  response.elements["searchresults"]
@@ -179,6 +179,11 @@ def search_osm_nominatim
       if klass == "boundary" && type == "administrative"
         rank = (place.attributes["place_rank"].to_i + 1) / 2
         prefix_name = t "geocoder.search_osm_nominatim.admin_levels.level#{rank}", :default => prefix_name
+        place.elements["extratags"].elements.each("tag") do |extratag|
+          if extratag.attributes["key"] == "place"
+            prefix_name = t "geocoder.search_osm_nominatim.prefix.place.#{extratag.attributes["value"]}", :default => prefix_name
+          end
+        end
       end
       prefix = t "geocoder.search_osm_nominatim.prefix_format", :name => prefix_name
       object_type = place.attributes["osm_type"]

test/controllers/geocoder_controller_test.rb

@@ -387,7 +387,7 @@ def test_search_osm_nominatim
                       "min-lat" => 51.7265723, "max-lat" => 51.7665723,
                       "min-lon" => -0.0390782, "max-lon" => 0.0009218,
                       "type" => "node", "id" => 28825933 },
-                    { "prefix" => "City Boundary",
+                    { "prefix" => "Village",
                       "name" => "Broxbourne, Hertfordshire, East of England, England, United Kingdom",
                       "min-lat" => 51.6808751, "max-lat" => 51.7806237,
                       "min-lon" => -0.114204, "max-lon" => 0.0145267,

test/http/nominatim.yml

@@ -6,14 +6,14 @@
       <place place_id='110741' osm_type='node' osm_id='18007599' place_rank='18' boundingbox="51.7216709,51.8016709,-0.0512898,0.0287102" lat='51.7616709' lon='-0.0112898' display_name='Hoddesdon, Hertfordshire, East of England, England, United Kingdom' class='place' type='town' importance='0.50547792382382' icon='http://nominatim.openstreetmap.org/images/mapicons/poi_place_town.p.20.png'/>
     </searchresults>
   
-/search?accept-language=&format=xml&q=Broxbourne&viewbox=-0.559%2C51.766%2C0.836%2C51.217:
+/search?accept-language=&format=xml&extratags=1&q=Broxbourne&viewbox=-0.559%2C51.766%2C0.836%2C51.217:
   code: 200
   body: |
     <?xml version="1.0" encoding="UTF-8" ?>
     <searchresults timestamp='Sun, 01 Mar 15 20:42:25 +0000' attribution='Data © OpenStreetMap contributors, ODbL 1.0. http://www.openstreetmap.org/copyright' querystring='Broxbourne' viewbox='-0.559,51.766,0.836,51.217' polygon='false' exclude_place_ids='150696,127984131,109724' more_url='http://nominatim.openstreetmap.org/search?format=xml&amp;exclude_place_ids=150696,127984131,109724&amp;viewbox=-0.559%2C51.766%2C0.836%2C51.217&amp;q=Broxbourne'>
-      <place place_id='150696' osm_type='node' osm_id='28825933' place_rank='20' boundingbox="51.7265723,51.7665723,-0.0390782,0.0009218" lat='51.7465723' lon='-0.0190782' display_name='Broxbourne, Hertfordshire, East of England, England, United Kingdom' class='place' type='suburb' importance='0.52141385408531' icon='http://nominatim.openstreetmap.org/images/mapicons/poi_place_village.p.20.png'/>
-      <place place_id='127984131' osm_type='relation' osm_id='2677978' place_rank='16' boundingbox="51.6808751,51.7806237,-0.114204,0.0145267" lat='51.73083995' lon='-0.0579457295222991' display_name='Broxbourne, Hertfordshire, East of England, England, United Kingdom' class='boundary' type='administrative' importance='0.46' icon='http://nominatim.openstreetmap.org/images/mapicons/poi_boundary_administrative.p.20.png'/>
-      <place place_id='109724' osm_type='node' osm_id='17044599' place_rank='30' boundingbox="51.7418469,51.7518469,-0.0156773,-0.0056773" lat='51.7468469' lon='-0.0106773' display_name='Broxbourne, Stafford Drive, Broxbourne, Hertfordshire, East of England, England, United Kingdom' class='railway' type='station' importance='0.111' icon='http://nominatim.openstreetmap.org/images/mapicons/transport_train_station2.p.20.png'/>
+      <place place_id='150696' osm_type='node' osm_id='28825933' place_rank='20' boundingbox="51.7265723,51.7665723,-0.0390782,0.0009218" lat='51.7465723' lon='-0.0190782' display_name='Broxbourne, Hertfordshire, East of England, England, United Kingdom' class='place' type='suburb' importance='0.52141385408531' icon='http://nominatim.openstreetmap.org/images/mapicons/poi_place_village.p.20.png'><extratags><tag key="wikipedia" value="en:Broxbourne"/></extratags></place>
+      <place place_id='127984131' osm_type='relation' osm_id='2677978' place_rank='16' boundingbox="51.6808751,51.7806237,-0.114204,0.0145267" lat='51.73083995' lon='-0.0579457295222991' display_name='Broxbourne, Hertfordshire, East of England, England, United Kingdom' class='boundary' type='administrative' importance='0.46' icon='http://nominatim.openstreetmap.org/images/mapicons/poi_boundary_administrative.p.20.png'><extratags><tag key="place" value="village"/></extratags></place>
+      <place place_id='109724' osm_type='node' osm_id='17044599' place_rank='30' boundingbox="51.7418469,51.7518469,-0.0156773,-0.0056773" lat='51.7468469' lon='-0.0106773' display_name='Broxbourne, Stafford Drive, Broxbourne, Hertfordshire, East of England, England, United Kingdom' class='railway' type='station' importance='0.111' icon='http://nominatim.openstreetmap.org/images/mapicons/transport_train_station2.p.20.png'><extratags></extratags></place>
     </searchresults>
   
 /reverse?accept-language=&lat=51.7632&lon=-0.0076&zoom=15: