Merge pull request #4332 from fredj/geojson_id_0_write

Fix write out GeoJSON features with id equal to 0

src/ol/format/geojsonformat.js

@@ -530,7 +530,7 @@ ol.format.GeoJSON.prototype.writeFeatureObject = function(
     'type': 'Feature'
   };
   var id = feature.getId();
-  if (id) {
+  if (id !== undefined) {
     object['id'] = id;
   }
   var geometry = feature.getGeometry();

test/spec/ol/format/geojsonformat.test.js

@@ -551,6 +551,12 @@ describe('ol.format.GeoJSON', function() {
       expect(geojson.geometry).to.eql(null);
     });
 
+    it('writes out a feature with id equal to 0 correctly', function() {
+      var feature = new ol.Feature();
+      feature.setId(0);
+      var geojson = format.writeFeatureObject(feature);
+      expect(geojson.id).to.eql(0);
+    });
   });
 
   describe('#writeGeometry', function() {