fix(ngOptions): don't duplicate groups with falsy values

Previously, ngOptions would fail to remove optgroups with falsy values when the options were changed / removed.

Related #14781 
PR (#14784)

src/ng/directive/ngOptions.js

@@ -629,7 +629,7 @@ var ngOptionsDirective = ['$compile', '$document', '$parse', function($compile,
 
           for (var i = options.items.length - 1; i >= 0; i--) {
             var option = options.items[i];
-            if (option.group) {
+            if (isDefined(option.group)) {
               jqLiteRemove(option.element.parentNode);
             } else {
               jqLiteRemove(option.element);
@@ -661,7 +661,8 @@ var ngOptionsDirective = ['$compile', '$document', '$parse', function($compile,
               listFragment.appendChild(groupElement);
 
               // Update the label on the group element
-              groupElement.label = option.group;
+              // "null" is special cased because of Safari
+              groupElement.label = option.group === null ? 'null' : option.group;
 
               // Store it for use later
               groupElementMap[option.group] = groupElement;

test/ng/directive/ngOptionsSpec.js

@@ -1789,6 +1789,87 @@ describe('ngOptions', function() {
     });
 
 
+    it('should group if the group has a falsy value (except undefined)', function() {
+      createSelect({
+        'ng-model': 'selected',
+        'ng-options': 'item.name group by item.group for item in values'
+      });
+
+      scope.$apply(function() {
+        scope.values = [{name: 'A'},
+                        {name: 'B', group: ''},
+                        {name: 'C', group: null},
+                        {name: 'D', group: false},
+                        {name: 'E', group: 0}];
+        scope.selected = scope.values[0];
+      });
+
+      var optgroups = element.find('optgroup');
+      var options = element.find('option');
+
+      expect(optgroups.length).toEqual(4);
+      expect(options.length).toEqual(5);
+
+      expect(optgroups[0].label).toBe('');
+      expect(optgroups[1].label).toBe('null');
+      expect(optgroups[2].label).toBe('false');
+      expect(optgroups[3].label).toBe('0');
+
+      expect(options[0].textContent).toBe('A');
+      expect(options[0].parentNode).toBe(element[0]);
+
+      expect(options[1].textContent).toBe('B');
+      expect(options[1].parentNode).toBe(optgroups[0]);
+
+      expect(options[2].textContent).toBe('C');
+      expect(options[2].parentNode).toBe(optgroups[1]);
+
+      expect(options[3].textContent).toBe('D');
+      expect(options[3].parentNode).toBe(optgroups[2]);
+
+      expect(options[4].textContent).toBe('E');
+      expect(options[4].parentNode).toBe(optgroups[3]);
+    });
+
+
+    it('should not duplicate a group with a falsy value when the options are updated', function() {
+
+      scope.$apply(function() {
+        scope.values = [{value: 'A', group: ''},
+                        {value: 'B', group: 'First'}];
+        scope.selected = scope.values[0];
+      });
+
+      createSelect({
+        'ng-model': 'selected',
+        'ng-options': 'item.value group by item.group for item in values'
+      });
+
+      scope.$apply(function() {
+        scope.values.push({value: 'C', group: false});
+      });
+
+      var optgroups = element.find('optgroup');
+      var options = element.find('option');
+
+      expect(optgroups.length).toEqual(3);
+      expect(options.length).toEqual(3);
+
+      expect(optgroups[0].label).toBe('');
+      expect(optgroups[1].label).toBe('First');
+      expect(optgroups[2].label).toBe('false');
+
+      expect(options[0].textContent).toBe('A');
+      expect(options[0].parentNode).toBe(optgroups[0]);
+
+      expect(options[1].textContent).toBe('B');
+      expect(options[1].parentNode).toBe(optgroups[1]);
+
+      expect(options[2].textContent).toBe('C');
+      expect(options[2].parentNode).toBe(optgroups[2]);
+    });
+
+
     it('should bind to scope value and track/identify objects', function() {
       createSelect({
         'ng-model': 'selected',