Define the extra tags separately, to save repetition. Refs #1

Author: gravitystorm

examples/openstreetmap-carto-legend.json

@@ -6,51 +6,52 @@
     {
       "name": "motorway",
       "type": "linestring",
-      "tags": { "feature": "highway_motorway", "cycleway": null, "service": null, "tunnel": null, "bicycle": null, "bridge": null, "construction": null, "highway": "motorway", "foot": null, "horse": null, "tracktype": null },
+      "tags": { "feature": "highway_motorway", "highway": "motorway" },
       "layers": ["roads-casing", "roads-fill"],
       "zoom": 18
     },
     {
       "name": "motorway",
       "type": "linestring",
-      "tags": { "feature": "highway_motorway", "cycleway": null, "service": null, "tunnel": null, "bicycle": null, "bridge": null, "construction": null, "highway": "motorway", "foot": null, "horse": null, "tracktype": null },
+      "tags": { "feature": "highway_motorway", "highway": "motorway" },
       "layers": ["roads-casing", "roads-fill"],
       "zoom": 15
     },
     {
       "name": "motorway",
       "type": "linestring",
-      "tags": { "feature": "highway_motorway", "cycleway": null, "service": null, "tunnel": null, "bicycle": null, "bridge": null, "construction": null, "highway": "motorway", "foot": null, "horse": null, "tracktype": null },
+      "tags": { "feature": "highway_motorway", "highway": "motorway" },
       "layers": ["roads-low-zoom"],
       "zoom": 6
     },
     {
       "name": "residential",
       "type": "linestring",
-      "tags": { "feature": "highway_residential", "cycleway": null, "service": null, "tunnel": "", "bicycle": null, "bridge": null, "construction": null, "highway": "residential", "foot": null, "horse": null, "tracktype": null },
+      "tags": { "feature": "highway_residential", "highway": "residential" },
       "layers": ["roads-casing", "roads-fill"],
       "zoom": 15
     },
     {
       "name": "residential",
       "type": "linestring",
-      "tags": { "feature": "highway_footway", "cycleway": null, "service": null, "tunnel": null, "bicycle": null, "bridge": null, "construction": null, "highway": "footway", "foot": null, "horse": null, "tracktype": null },
+      "tags": { "feature": "highway_footway", "highway": "footway" },
       "layers": ["roads-casing", "roads-fill"],
       "zoom": 15
     },
     {
       "name": "pub",
       "type": "point",
-      "tags": { "amenity": "pub", "access": null, "highway": null, "historic": null, "leisure": null, "lock": null, "man_made": null, "religion": null, "shop": null, "tourism": null, "waterway": null },
+      "tags": { "amenity": "pub" },
       "layers": ["amenity-points"],
       "zoom": 16
     },
     {
       "name": "park",
       "type": "polygon",
-      "tags": { "feature": "leisure_park", "religion": null },
+      "tags": { "feature": "leisure_park" },
       "layers": ["landcover"],
       "zoom": 15
     }
-  ]
+  ],
+  "extra_tags": ["feature", "cycleway", "service", "tunnel", "bicycle", "bridge", "construction", "highway", "foot", "horse", "tracktype", "access", "historic", "leisure", "lock", "man_made", "religion", "shop", "tourism", "waterway"]
 }

lib/mapnik_legendary.rb

@@ -2,6 +2,7 @@
 require 'json'
 
 require 'mapnik_legendary/geometry'
+require 'mapnik_legendary/tags'
 
 module MapnikLegendary
   DEFAULT_ZOOM = 17
@@ -29,8 +30,9 @@ def self.generate_legend(legend_file, map_file, options)
       # TODO - use a proper csv library rather than .join(",") !
       zoom = feature["zoom"] || DEFAULT_ZOOM
       geom = Geometry.new(feature["type"], zoom, map).to_csv
-      header = feature["tags"].keys.push("wkt").join(",")
-      row = feature["tags"].values.push(geom).join(",")
+      tags = Tags.merge_nulls(feature["tags"], legend["extra_tags"])
+      header = tags.keys.push("wkt").join(",")
+      row = tags.values.push(geom).join(",")
       datasource = Mapnik::Datasource.create(:type => 'csv', :inline => header + "\n" + row )
 
       map.layers.clear

lib/mapnik_legendary/tags.rb

@@ -0,0 +1,7 @@
+module MapnikLegendary
+  class Tags
+    def self.merge_nulls(tags, extras)
+      Hash[extras.map{|t| [t,"null"]}].merge(tags)
+    end
+  end
+end