feat(uiSelectSingleDirective): add an option to avoid backspace model reset

src/common.js

@@ -106,7 +106,8 @@ var uis = angular.module('ui.select', [])
   generateId: function() {
     return latestId++;
   },
-  appendToBody: false
+  appendToBody: false,
+  disableBackspaceReset: false
 })
 
 // See Rename minErr and make it accessible from outside https://github.com/angular/angular.js/issues/6913

src/uiSelectDirective.js

@@ -83,6 +83,10 @@ uis.directive('uiSelect',
             $select.sortable = sortable !== undefined ? sortable : uiSelectConfig.sortable;
         });
 
+        scope.$watch(function () { return scope.$eval(attrs.disableBackspaceReset); }, function(newVal) {
+          $select.disableBackspaceReset = newVal !== undefined ? newVal : uiSelectConfig.disableBackspaceReset;
+        });
+
         attrs.$observe('limit', function() {
           //Limit the number of selections allowed
           $select.limit = (angular.isDefined(attrs.limit)) ? parseInt(attrs.limit, 10) : undefined;

src/uiSelectSingleDirective.js

@@ -85,7 +85,7 @@ uis.directive('uiSelectSingle', ['$timeout','$compile', function($timeout, $comp
       });
       focusser.bind("keydown", function(e){
 
-        if (e.which === KEY.BACKSPACE) {
+        if (e.which === KEY.BACKSPACE && $select.disableBackspaceReset === false) {
           e.preventDefault();
           e.stopPropagation();
           $select.select(undefined);

test/select.spec.js

@@ -161,6 +161,7 @@ describe('ui-select tests', function() {
       if (attrs.ngClass !== undefined) { attrsHtml += ' ng-class="' + attrs.ngClass + '"'; }
       if (attrs.resetSearchInput !== undefined) { attrsHtml += ' reset-search-input="' + attrs.resetSearchInput + '"'; }
       if (attrs.closeOnSelect !== undefined) { attrsHtml += ' close-on-select="' + attrs.closeOnSelect + '"'; }
+      if (attrs.disableBackspaceReset !== undefined) { attrsHtml += ' disable-backspace-reset="' + attrs.disableBackspaceReset + '"';}
     }
 
     return compileTemplate(
@@ -802,6 +803,26 @@ describe('ui-select tests', function() {
     expect(getMatchLabel(el)).toEqual('-- None Selected --');
   });
 
+  describe('disable backspace reset option', function(){
+    it('should undefined model when pressing BACKSPACE key if disableBackspaceReset=false', function() {
+      var el = createUiSelect();
+      var focusserInput = el.find('.ui-select-focusser');
+
+      clickItem(el, 'Samantha');
+      triggerKeydown(focusserInput, Key.Backspace);
+      expect(scope.selection.selected).toBeUndefined();
+    });
+
+    it('should NOT reset model when pressing BACKSPACE key if disableBackspaceReset=true', function() {
+      var el = createUiSelect({disableBackspaceReset: true});
+      var focusserInput = el.find('.ui-select-focusser');
+
+      clickItem(el, 'Samantha');
+      triggerKeydown(focusserInput, Key.Backspace);
+      expect(scope.selection.selected).toBe(scope.people[5]);
+    });
+  });
+
   describe('disabled options', function() {
     function createUiSelect(attrs) {
       var attrsDisabled = '';