[BUGFIX release] Fixing IE and Edge issue (#15076) which caused actio…

…n handlers to be fired twice.

packages/ember-glimmer/tests/integration/helpers/element-action-test.js

@@ -1423,4 +1423,38 @@ moduleFor('Helpers test: element action', class extends RenderingTest {
 
     this.assertText('Click me');
   }
+
+  ['@test action handler that shifts element attributes doesn\'t trigger multiple invocations']() {
+    let actionCount = 0;
+    let ExampleComponent = Component.extend({
+      selected: false,
+      actions: {
+        toggleSelected() {
+          actionCount++;
+          this.toggleProperty('selected');
+        }
+      }
+    });
+
+    this.registerComponent('example-component', {
+      ComponentClass: ExampleComponent,
+      template: '<button class="{{if selected \'selected\'}}" {{action "toggleSelected"}}>Toggle Selected</button>'
+    });
+
+    this.render('{{example-component}}');
+
+    this.runTask(() => {
+      this.$('button').click();
+    });
+
+    this.assert.equal(actionCount, 1, 'Click action only fired once.');
+    this.assert.ok(this.$('button').hasClass('selected'), 'Element with action handler has properly updated it\'s conditional class');
+
+    this.runTask(() => {
+      this.$('button').click();
+    });
+
+    this.assert.equal(actionCount, 2, 'Second click action only fired once.');
+    this.assert.ok(!this.$('button').hasClass('selected'), 'Element with action handler has properly updated it\'s conditional class');
+  }
 });

packages/ember-views/lib/system/event_dispatcher.js

@@ -220,6 +220,7 @@ export default EmberObject.extend({
 
     rootElement.on(`${event}.ember`, '[data-ember-action]', evt => {
       let attributes = evt.currentTarget.attributes;
+      let handledActions = [];
 
       for (let i = 0; i < attributes.length; i++) {
         let attr = attributes.item(i);
@@ -231,8 +232,12 @@ export default EmberObject.extend({
           // We have to check for action here since in some cases, jQuery will trigger
           // an event on `removeChild` (i.e. focusout) after we've already torn down the
           // action handlers for the view.
-          if (action && action.eventName === eventName) {
+          if (action && action.eventName === eventName && handledActions.indexOf(action) === -1) {
             action.handler(evt);
+            // Action handlers can mutate state which in turn creates new attributes on the element.
+            // This effect could cause the `data-ember-action` attribute to shift down and be invoked twice.
+            // To avoid this, we keep track of which actions have been handled.
+            handledActions.push(action);
           }
         }
       }