fix(htmlAnchorDirective): remove event listener if target is not element

Previously, when an `a` tag element used a directive with a replacing template, and did not include an `href` or `name` attribute
before linkage, the anchor directive would always prevent default.

Now, the anchor directive will cancel its event listener if the linked element is not the same as the target element of the event.

Closes angular#4262

src/ng/directive/a.js

@@ -18,10 +18,16 @@ var htmlAnchorDirective = valueFn({
   compile: function(element, attr) {
     if (!attr.href && !attr.xlinkHref && !attr.name) {
       return function(scope, element) {
+        // If the linked element is not an anchor tag anymore, do nothing
+        if (element[0].nodeName.toLowerCase() !== 'a') return;
+
         // SVGAElement does not use the href attribute, but rather the 'xlinkHref' attribute.
         var href = toString.call(element.prop('href')) === '[object SVGAnimatedString]' ?
                    'xlink:href' : 'href';
-        element.on('click', function(event) {
+        element.on('click', function clickHandler(event) {
+          // If a different element was clicked, ignore it.
+          if (element[0] !== event.target) return;
+
           // if we have no href url, then don't navigate anywhere.
           if (!element.attr(href)) {
             event.preventDefault();

test/ng/directive/aSpec.js

@@ -3,6 +3,25 @@
 describe('a', function() {
   var element, $compile, $rootScope;
 
+  beforeEach(module(function($compileProvider) {
+    $compileProvider.
+      directive('linkTo', valueFn({
+        restrict: 'A',
+        template: '<div class="my-link"><a href="{{destination}}">{{destination}}</a></div>',
+        replace: true,
+        scope: {
+          destination: '@linkTo'
+        }
+      })).
+      directive('linkNot', valueFn({
+        restrict: 'A',
+        template: '<div class="my-link"><a href>{{destination}}</a></div>',
+        replace: true,
+        scope: {
+          destination: '@linkNot'
+        }
+      }));
+  }));
 
   beforeEach(inject(function(_$compile_, _$rootScope_) {
     $compile = _$compile_;
@@ -76,6 +95,40 @@ describe('a', function() {
   });
 
 
+  it('should not preventDefault if anchor element is replaced with href-containing element', function() {
+    spyOn(jqLite.prototype, 'on').andCallThrough();
+    element = $compile('<a link-to="https://www.google.com">')($rootScope);
+    $rootScope.$digest();
+
+    var child = element.children('a');
+    var preventDefault = jasmine.createSpy('preventDefault');
+
+    child.triggerHandler({
+      type: 'click',
+      preventDefault: preventDefault
+    });
+
+    expect(preventDefault).not.toHaveBeenCalled();
+  });
+
+
+  it('should preventDefault if anchor element is replaced with element without href attribute', function() {
+    spyOn(jqLite.prototype, 'on').andCallThrough();
+    element = $compile('<a link-not="https://www.google.com">')($rootScope);
+    $rootScope.$digest();
+
+    var child = element.children('a');
+    var preventDefault = jasmine.createSpy('preventDefault');
+
+    child.triggerHandler({
+      type: 'click',
+      preventDefault: preventDefault
+    });
+
+    expect(preventDefault).toHaveBeenCalled();
+  });
+
+
   if (isDefined(window.SVGElement)) {
     describe('SVGAElement', function() {
       it('should prevent default action to be executed when href is empty', function() {