allow hydrating clustered features

src/ol/source/Cluster.js

@@ -38,6 +38,8 @@ import {getUid} from '../util.js';
  *   return feature.getGeometry();
  * }
  * ```
+ * @property {function(Feature, Array<Feature>):any} [hydrate] Function called after creating
+ * cluster feature
  * See {@link module:ol/geom/Polygon~Polygon#getInteriorPoint} for a way to get a cluster
  * calculation point for polygons.
  * @property {VectorSource} [source] Source.
@@ -108,6 +110,12 @@ class Cluster extends VectorSource {
         return geometry;
       };
 
+    /**
+     * @type {function(Feature, Array<Feature>):any}
+     * @protected
+     */
+    this.hydrate = options.hydrate;
+
     /**
      * @type {VectorSource}
      * @protected
@@ -295,6 +303,9 @@ class Cluster extends VectorSource {
       centroid[1] * (1 - ratio) + searchCenter[1] * ratio,
     ]);
     const cluster = new Feature(geometry);
+    if (this.hydrate) {
+      this.hydrate(cluster, features);
+    }
     cluster.set('features', features, true);
     return cluster;
   }

test/browser/spec/ol/source/cluster.test.js

@@ -75,6 +75,23 @@ describe('ol.source.Cluster', function () {
       expect(source.getFeatures().length).to.be(1);
       expect(source.getFeatures()[0].get('features').length).to.be(2);
     });
+    it('hydrates cluster feature with additional fields', function () {
+      const feature1 = new Feature(new Point([0, 0]));
+      const feature2 = new Feature(new Point([0, 0]));
+      feature1.set('value', 1);
+      feature2.set('value', 2);
+      const source = new Cluster({
+        source: new VectorSource({
+          features: [feature1, feature2],
+        }),
+        hydrate: function (clusterFeature, features) {
+          clusterFeature.set('sum', 3);
+        },
+      });
+      source.loadFeatures(extent, 1, projection);
+      expect(source.getFeatures().length).to.be(1);
+      expect(source.getFeatures()[0].get('sum')).to.be(3);
+    });
   });
 
   describe('#setDistance', function () {