Allow once listeners to dispatch events of same type

src/ol/events/eventtarget.js

@@ -33,6 +33,12 @@ ol.events.EventTarget = function() {
    */
   this.pendingRemovals_ = {};
 
+  /**
+   * @private
+   * @type {!Object.<string, number>}
+   */
+  this.dispatching_ = {};
+
   /**
    * @private
    * @type {!Object.<string, Array.<ol.events.ListenerFunctionType>>}
@@ -72,19 +78,25 @@ ol.events.EventTarget.prototype.dispatchEvent = function(event) {
   var listeners = this.listeners_[type];
   var propagate;
   if (listeners) {
-    if (!(type in this.pendingRemovals_)) {
+    if (!(type in this.dispatching_)) {
+      this.dispatching_[type] = 0;
       this.pendingRemovals_[type] = 0;
     }
+    ++this.dispatching_[type];
     for (var i = 0, ii = listeners.length; i < ii; ++i) {
       if (listeners[i].call(this, evt) === false || evt.propagationStopped) {
         propagate = false;
         break;
       }
     }
-    var pendingRemovals = this.pendingRemovals_[type];
-    delete this.pendingRemovals_[type];
-    while (pendingRemovals--) {
-      this.removeEventListener(type, ol.nullFunction);
+    --this.dispatching_[type];
+    if (this.dispatching_[type] === 0) {
+      var pendingRemovals = this.pendingRemovals_[type];
+      delete this.pendingRemovals_[type];
+      while (pendingRemovals--) {
+        this.removeEventListener(type, ol.nullFunction);
+      }
+      delete this.dispatching_[type];
     }
     return propagate;
   }

test/spec/ol/observable.test.js

@@ -73,6 +73,21 @@ describe('ol.Observable', function() {
       expect(listener.callCount).to.be(1);
     });
 
+    it('is safe to dispatch events of same type in a once listener', function() {
+      var callCount = 0;
+      observable.once('change', function() {
+        observable.changed();
+        observable.changed();
+      });
+      observable.on('change', function() {
+        ++callCount;
+      });
+      expect(function() {
+        observable.changed();
+      }).to.not.throwException();
+      expect(callCount).to.be(3);
+    });
+
     it('accepts an array of event types (called once for each)', function() {
       observable.once(['foo', 'bar'], listener);