why angularjs link function is never called?

Angularjs link function is never called.

The source code is included in webpack bundle.

angular version is v1.6.6

import angular from 'angular';

const module = angular.module('app.directives.ax', []);

console.log('included directive');
module.directive('ax', function() {
  return {
    restrict: 'AEC',
    link: function(scope, elem, attrs) {
      console.log('from directive');
      console.log('from directive xxx');
      elem.css('cursor', 'pointer');
      if (attrs.ngClick || attrs.href === '' || attrs.href === '#') {
        elem.on('click', function(e){
          e.preventDefault();
        });
      }
    }
 };
});

export default module.name;

In the html template I have

<a class="default-link ax" ng-click="vm.delete(announcement.id)"><i class="fa fa-trash-o"></i></a>