Vector Source / index all features by uid

Previously features were indexed by uid only when they
did not have a defined id.
A new method was added: `getFeatureByUid`. This is not part of
the public API.
This will facilitate the lookup of features for hit detection.

src/ol/source/Vector.js

@@ -241,11 +241,11 @@ class VectorSource extends Source {
     this.idIndex_ = {};
 
     /**
-     * A lookup of features without id (keyed by getUid(feature)).
+     * A lookup of features by uid (using getUid(feature)).
      * @private
      * @type {!Object<string, import("../Feature.js").default<Geometry>>}
      */
-    this.undefIdIndex_ = {};
+    this.uidIndex_ = {};
 
     /**
      * @private
@@ -359,10 +359,11 @@ class VectorSource extends Source {
       } else {
         valid = false;
       }
-    } else {
-      assert(!(featureKey in this.undefIdIndex_),
+    }
+    if (valid) {
+      assert(!(featureKey in this.uidIndex_),
         30); // The passed `feature` was already added to the source
-      this.undefIdIndex_[featureKey] = feature;
+      this.uidIndex_[featureKey] = feature;
     }
     return valid;
   }
@@ -489,7 +490,7 @@ class VectorSource extends Source {
       if (!this.featuresCollection_) {
         this.featureChangeKeys_ = {};
         this.idIndex_ = {};
-        this.undefIdIndex_ = {};
+        this.uidIndex_ = {};
       }
     } else {
       if (this.featuresRtree_) {
@@ -770,6 +771,18 @@ class VectorSource extends Source {
   }
 
 
+  /**
+   * Get a feature by its internal unique identifier (using `getUid`).
+   *
+   * @param {string} uid Feature identifier.
+   * @return {import("../Feature.js").default<Geometry>} The feature (or `null` if not found).
+   */
+  getFeatureByUid(uid) {
+    const feature = this.uidIndex_[uid];
+    return feature !== undefined ? feature : null;
+  }
+
+
   /**
    * Get the format associated with this source.
    *
@@ -831,20 +844,13 @@ class VectorSource extends Source {
     const id = feature.getId();
     if (id !== undefined) {
       const sid = id.toString();
-      if (featureKey in this.undefIdIndex_) {
-        delete this.undefIdIndex_[featureKey];
+      if (this.idIndex_[sid] !== feature) {
+        this.removeFromIdIndex_(feature);
         this.idIndex_[sid] = feature;
-      } else {
-        if (this.idIndex_[sid] !== feature) {
-          this.removeFromIdIndex_(feature);
-          this.idIndex_[sid] = feature;
-        }
       }
     } else {
-      if (!(featureKey in this.undefIdIndex_)) {
-        this.removeFromIdIndex_(feature);
-        this.undefIdIndex_[featureKey] = feature;
-      }
+      this.removeFromIdIndex_(feature);
+      this.uidIndex_[featureKey] = feature;
     }
     this.changed();
     this.dispatchEvent(new VectorSourceEvent(
@@ -862,7 +868,7 @@ class VectorSource extends Source {
     if (id !== undefined) {
       return id in this.idIndex_;
     } else {
-      return getUid(feature) in this.undefIdIndex_;
+      return getUid(feature) in this.uidIndex_;
     }
   }
 
@@ -964,9 +970,8 @@ class VectorSource extends Source {
     const id = feature.getId();
     if (id !== undefined) {
       delete this.idIndex_[id.toString()];
-    } else {
-      delete this.undefIdIndex_[featureKey];
     }
+    delete this.uidIndex_[featureKey];
     this.dispatchEvent(new VectorSourceEvent(
       VectorEventType.REMOVEFEATURE, feature));
   }

test/spec/ol/source/vector.test.js

@@ -10,6 +10,7 @@ import {bbox as bboxStrategy} from '../../../../src/ol/loadingstrategy.js';
 import {get as getProjection, transformExtent, fromLonLat} from '../../../../src/ol/proj.js';
 import VectorSource from '../../../../src/ol/source/Vector.js';
 import GeoJSON from '../../../../src/ol/format/GeoJSON.js';
+import {getUid} from '../../../../src/ol/util.js';
 
 
 describe('ol.source.Vector', function() {
@@ -519,6 +520,59 @@ describe('ol.source.Vector', function() {
 
   });
 
+  describe('#getFeatureByUid()', function() {
+    let source;
+    beforeEach(function() {
+      source = new VectorSource();
+    });
+
+    it('returns a feature with an id', function() {
+      const feature = new Feature();
+      feature.setId('abcd');
+      source.addFeature(feature);
+      expect(source.getFeatureByUid(getUid(feature))).to.be(feature);
+    });
+
+    it('returns a feature without id', function() {
+      const feature = new Feature();
+      source.addFeature(feature);
+      expect(source.getFeatureByUid(getUid(feature))).to.be(feature);
+    });
+
+    it('returns null when no feature is found', function() {
+      const feature = new Feature();
+      feature.setId('abcd');
+      source.addFeature(feature);
+      const wrongId = 'abcd';
+      expect(source.getFeatureByUid(wrongId)).to.be(null);
+    });
+
+    it('returns null after removing feature', function() {
+      const feature = new Feature();
+      feature.setId('abcd');
+      source.addFeature(feature);
+      const uid = getUid(feature);
+      expect(source.getFeatureByUid(uid)).to.be(feature);
+      source.removeFeature(feature);
+      expect(source.getFeatureByUid(uid)).to.be(null);
+    });
+
+    it('returns null after clear', function() {
+      const feature = new Feature();
+      feature.setId('abcd');
+      source.addFeature(feature);
+      const uid = getUid(feature);
+      expect(source.getFeatureByUid(uid)).to.be(feature);
+      source.clear();
+      expect(source.getFeatureByUid(uid)).to.be(null);
+    });
+
+    it('returns null when no features are present', function() {
+      expect(source.getFeatureByUid('abcd')).to.be(null);
+    });
+
+  });
+
   describe('#loadFeatures', function() {
 
     describe('with the "bbox" strategy', function() {