fix(ngShow/ngHide, ngIf): functions with zero args should be truthy

Previously, expressions that were a function with one or more arguments evaluated to
true, but functions with zero arguments evaluated to false.

This behavior seems both unintentional and undesirable. This patch makes a function
truthy regardless of its number of arguments.

Closes angular#5414

src/Angular.js

@@ -959,7 +959,9 @@ function fromJson(json) {
 
 
 function toBoolean(value) {
- if (value && value.length !== 0) {
+ if (typeof value === 'function') {
+ value = true;
+ } else if (value && value.length !== 0) {
  var v = lowercase("" + value);
  value = !(v == 'f' || v == '0' || v == 'false' || v == 'no' || v == 'n' || v == '[]');
  } else {

test/ng/directive/ngShowHideSpec.js

@@ -20,6 +20,16 @@ describe('ngShow / ngHide', function() {
  }));
 
 
+ // https://github.com/angular/angular.js/issues/5414
+ it('should show if the expression is a function with a no arguments', inject(function($rootScope, $compile) {
+ element = jqLite('<div ng-show="exp"></div>');
+ element = $compile(element)($rootScope);
+ $rootScope.exp = function(){};
+ $rootScope.$digest();
+ expect(element).toBeShown();
+ }));
+
+
  it('should make hidden element visible', inject(function($rootScope, $compile) {
  element = jqLite('<div class="ng-hide" ng-show="exp"></div>');
  element = $compile(element)($rootScope);