Fixes #363, allow displayName to be empty string

When the columnDef displayName property was an empty string, the column
class was defaulting to using the field name in the header template. Now
it will allow an empty string and will only use the field name if
displayName is undefined.

src/classes/column.js

@@ -12,7 +12,10 @@
     self.maxWidth = !colDef.maxWidth ? 9000 : colDef.maxWidth;
 	self.enableCellEdit = config.enableCellEdit || colDef.enableCellEdit;
     self.headerRowHeight = config.headerRowHeight;
-    self.displayName = colDef.displayName || colDef.field;
+
+    // Use colDef.displayName as long as it's not undefined, otherwise default to the field name
+    self.displayName = (colDef.displayName === undefined) ? colDef.field : colDef.displayName;
+
     self.index = config.index;
     self.isAggCol = config.isAggCol;
     self.cellClass = colDef.cellClass;

test/unit/directivesSpec.js

@@ -88,8 +88,38 @@ describe('directives', function () {
                 });
             });
             describe('column', function () {
-                it('should do something', function () {
-                    //add work here
+                beforeEach(inject(function ($rootScope, $domUtilityService, $templateCache, $compile) {
+                    $scope = $rootScope.$new();
+                    $dUtils = $domUtilityService;
+                    $linker = $compile;
+                    $cache = $templateCache;
+
+                    elm = angular.element(
+                        '<div ng-grid="gridOptions" style="width: 1000px; height: 1000px"></div>'
+                    );
+                    scope = $rootScope;
+                    scope.myData = [{name: "Moroni", age: 50},
+                                  {name: "Tiancum", age: 43},
+                                  {name: "Jacob", age: 27},
+                                  {name: "Nephi", age: 29},
+                                  {name: "Enos", age: 34}];
+                    scope.gridOptions = {
+                        data: 'myData',
+                        columnDefs: [
+                            { field : 'name' },
+                            { field : 'age', displayName: '' },
+                        ]
+                    };
+                    $compile(elm)(scope);
+                    scope.$digest();
+                }));
+
+                it('should default to the field name when displayName is undefined', function() {
+                    expect(elm.find('.ngHeaderText:eq(0)').text()).toEqual('name');
+                });
+
+                it('should not default to the column field name when the displayName is an empty string', function () {
+                    expect(elm.find('.ngHeaderText:eq(1)').text()).toEqual('');
                 });
             });
             describe('domAccessProvider', function () {