feat(button): allow uncheckable radio button

Acts as a hybrid checkbox/radio-button, selecting exclusively among the button set, but also allowing the selected item to be unselected, leaving the button set without a selected item.

Closes #1760

Author: duncanbeevers

Diff for: src/buttons/buttons.js

@@ -24,9 +24,11 @@ angular.module('ui.bootstrap.buttons', [])
 
       //ui->model
       element.bind(buttonsCtrl.toggleEvent, function () {
-        if (!element.hasClass(buttonsCtrl.activeClass)) {
+        var isActive = element.hasClass(buttonsCtrl.activeClass);
+
+        if (!isActive || angular.isDefined(attrs.uncheckable)) {
           scope.$apply(function () {
-            ngModelCtrl.$setViewValue(scope.$eval(attrs.btnRadio));
+            ngModelCtrl.$setViewValue(isActive ? null : scope.$eval(attrs.btnRadio));
             ngModelCtrl.$render();
           });
         }

Diff for: src/buttons/docs/demo.html

@@ -11,11 +11,16 @@ <h4>Checkbox</h4>
         <label class="btn btn-primary" ng-model="checkModel.middle" btn-checkbox>Middle</label>
         <label class="btn btn-primary" ng-model="checkModel.right" btn-checkbox>Right</label>
     </div>
-    <h4>Radio</h4>
-    <pre>{{radioModel}}</pre>
+    <h4>Radio &amp; Uncheckable Radio</h4>
+    <pre>{{radioModel || 'null'}}</pre>
     <div class="btn-group">
         <label class="btn btn-primary" ng-model="radioModel" btn-radio="'Left'">Left</label>
         <label class="btn btn-primary" ng-model="radioModel" btn-radio="'Middle'">Middle</label>
         <label class="btn btn-primary" ng-model="radioModel" btn-radio="'Right'">Right</label>
     </div>
+    <div class="btn-group">
+        <label class="btn btn-success" ng-model="radioModel" btn-radio="'Left'" uncheckable>Left</label>
+        <label class="btn btn-success" ng-model="radioModel" btn-radio="'Middle'" uncheckable>Middle</label>
+        <label class="btn btn-success" ng-model="radioModel" btn-radio="'Right'" uncheckable>Right</label>
+    </div>
 </div>

Diff for: src/buttons/docs/readme.md

@@ -1,2 +1 @@
-There are 2 directives that can make a group of buttons to behave like a set of checkboxes or radio buttons.
-
+There are two directives that can make a group of buttons behave like a set of checkboxes, radio buttons, or a hybrid where radio buttons can be unchecked.

Diff for: src/buttons/test/buttons.spec.js

@@ -136,5 +136,53 @@ describe('buttons', function () {
       expect(btns.eq(0)).not.toHaveClass('active');
       expect(btns.eq(1)).toHaveClass('active');
     });
+
+    describe('uncheckable', function () {
+      //model -> UI
+      it('should set active class based on model', function () {
+        var btns = compileButtons('<button ng-model="model" btn-radio="1" uncheckable>click1</button><button ng-model="model" btn-radio="2" uncheckable>click2</button>', $scope);
+        expect(btns.eq(0)).not.toHaveClass('active');
+        expect(btns.eq(1)).not.toHaveClass('active');
+
+        $scope.model = 2;
+        $scope.$digest();
+        expect(btns.eq(0)).not.toHaveClass('active');
+        expect(btns.eq(1)).toHaveClass('active');
+      });
+
+      //UI->model
+      it('should unset active class based on model', function () {
+        var btns = compileButtons('<button ng-model="model" btn-radio="1" uncheckable>click1</button><button ng-model="model" btn-radio="2" uncheckable>click2</button>', $scope);
+        expect($scope.model).toBeUndefined();
+
+        btns.eq(0).click();
+        expect($scope.model).toEqual(1);
+        expect(btns.eq(0)).toHaveClass('active');
+        expect(btns.eq(1)).not.toHaveClass('active');
+
+        btns.eq(0).click();
+        expect($scope.model).toEqual(undefined);
+        expect(btns.eq(1)).not.toHaveClass('active');
+        expect(btns.eq(0)).not.toHaveClass('active');
+      });
+
+      it('should watch btn-radio values and update state', function () {
+        $scope.values = ['value1', 'value2'];
+
+        var btns = compileButtons('<button ng-model="model" btn-radio="values[0]" uncheckable>click1</button><button ng-model="model" btn-radio="values[1]" uncheckable>click2</button>', $scope);
+        expect(btns.eq(0)).not.toHaveClass('active');
+        expect(btns.eq(1)).not.toHaveClass('active');
+
+        $scope.model = 'value2';
+        $scope.$digest();
+        expect(btns.eq(0)).not.toHaveClass('active');
+        expect(btns.eq(1)).toHaveClass('active');
+
+        $scope.model = undefined;
+        $scope.$digest();
+        expect(btns.eq(0)).not.toHaveClass('active');
+        expect(btns.eq(1)).not.toHaveClass('active');
+      });
+    });
   });
 });