fix(a): don't preventDefault on click when SVGAElement has an xlink:href attribute

Before this change, an SVGAElement with an xlink:href attribute and no href or name attribute which
was compiled by the angular HTML compiler would never be clickable, due to the htmlAnchorDirective
calling event.preventDefault() due to the missing href attribute.

This change corrects this behaviour by also testing the xlink:href attribute if the element in
question is determined to be an SVG anchor tag (with the href property having type SVGAnimatedString)

Closes #5896
Closes #5897

src/ng/directive/a.js

@@ -32,11 +32,14 @@ var htmlAnchorDirective = valueFn({
       element.append(document.createComment('IE fix'));
     }
 
-    if (!attr.href && !attr.name) {
+    if (!attr.href && !attr.xlinkHref && !attr.name) {
       return function(scope, element) {
+        // 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){
           // if we have no href url, then don't navigate anywhere.
-          if (!element.attr('href')) {
+          if (!element.attr(href)) {
             event.preventDefault();
           }
         });

test/ng/directive/aSpec.js

@@ -84,4 +84,71 @@ describe('a', function() {
 
     expect(jq.prototype.on).not.toHaveBeenCalled();
   });
+
+
+  if (isDefined(window.SVGElement)) {
+    describe('SVGAElement', function() {
+      it('should prevent default action to be executed when href is empty', function() {
+        var orgLocation = document.location.href,
+            preventDefaultCalled = false,
+            event,
+            child;
+
+        element = $compile('<svg><a xlink:href="">empty link</a></svg>')($rootScope);
+        child = element.children('a');
+
+        if (msie < 9) {
+
+          event = document.createEventObject();
+          expect(event.returnValue).not.toBeDefined();
+          child[0].fireEvent('onclick', event);
+          expect(event.returnValue).toEqual(false);
+
+        } else {
+
+          event = document.createEvent('MouseEvent');
+          event.initMouseEvent(
+            'click', true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
+
+          event.preventDefaultOrg = event.preventDefault;
+          event.preventDefault = function() {
+            preventDefaultCalled = true;
+            if (this.preventDefaultOrg) this.preventDefaultOrg();
+          };
+
+          child[0].dispatchEvent(event);
+
+          expect(preventDefaultCalled).toEqual(true);
+        }
+
+        expect(document.location.href).toEqual(orgLocation);
+      });
+
+
+      it('should not link and hookup an event if xlink:href is present at compile', function() {
+        var jq = jQuery || jqLite;
+        element = jq('<svg><a xlink:href="bobby">hello@you</a></svg>');
+        var linker = $compile(element);
+
+        spyOn(jq.prototype, 'on');
+
+        linker($rootScope);
+
+        expect(jq.prototype.on).not.toHaveBeenCalled();
+      });
+
+
+      it('should not link and hookup an event if name is present at compile', function() {
+        var jq = jQuery || jqLite;
+        element = jq('<svg><a name="bobby">hello@you</a></svg>');
+        var linker = $compile(element);
+
+        spyOn(jq.prototype, 'on');
+
+        linker($rootScope);
+
+        expect(jq.prototype.on).not.toHaveBeenCalled();
+      });
+    });
+  }
 });