From 442fa907ce236bff46bba8424eb9ab32fdb0a454 Mon Sep 17 00:00:00 2001
From: Olivier Guyot <olivier.guyot@camptocamp.com>
Date: Thu, 23 May 2019 11:35:39 +0200
Subject: [PATCH] Vector source / prevent adding features with duplicate id...

...in the collection.

Previously two features with the same id could be pushed manually in the
features collection and stay there.

This would cause an error when clearing the source.

Fixes #6183.
---
 src/ol/source/Vector.js            |  6 ++++++
 test/spec/ol/source/vector.test.js | 13 +++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/ol/source/Vector.js b/src/ol/source/Vector.js
index e44191b9fa..c72f777bbe 100644
--- a/src/ol/source/Vector.js
+++ b/src/ol/source/Vector.js
@@ -282,6 +282,9 @@ class VectorSource extends Source {
    * instead. A feature will not be added to the source if feature with
    * the same id is already there. The reason for this behavior is to avoid
    * feature duplication when using bbox or tile loading strategies.
+   * Note: this also applies if an {@link module:ol/Collection} is used for features,
+   * meaning that if a feature with a duplicate id is added in the collection, it will
+   * be removed from it right away.
    * @param {import("../Feature.js").default} feature Feature to add.
    * @api
    */
@@ -300,6 +303,9 @@ class VectorSource extends Source {
     const featureKey = getUid(feature);
 
     if (!this.addToIndex_(featureKey, feature)) {
+      if (this.featuresCollection_) {
+        this.featuresCollection_.remove(feature);
+      }
       return;
     }
 
diff --git a/test/spec/ol/source/vector.test.js b/test/spec/ol/source/vector.test.js
index 0223cec14f..d48d2962a3 100644
--- a/test/spec/ol/source/vector.test.js
+++ b/test/spec/ol/source/vector.test.js
@@ -719,6 +719,19 @@ describe('ol.source.Vector', function() {
       expect(source.getFeatures().length).to.be(0);
     });
 
+    it('prevents adding two features with a duplicate id in the collection', function() {
+      source = new VectorSource({
+        features: new Collection()
+      });
+      const feature1 = new Feature();
+      feature1.setId('1');
+      const feature2 = new Feature();
+      feature2.setId('1');
+      const collection = source.getFeaturesCollection();
+      collection.push(feature1);
+      collection.push(feature2);
+      expect(collection.getLength()).to.be(1);
+    });
   });
 
   describe('with a collection of features plus spatial index', function() {