fix(ngSrc): don't set src if value is empty string

Current implementation of ngSrc may lead to empty src attribute when page is loading.

For example:

<img ng-src="{{image.url}}">
can be temporarily rendered as

<img src="">
before the image resource is loaded.

Some browser emits a request to the current page when seeing <img src=""> (Firefox13 and IE8 will, Chromium20 won't), which leads to performance problems.

1 files changed, 17 insertions, 0 deletions

diff --git a/test/ng/directive/ngSrcSpec.js b/test/ng/directive/ngSrcSpec.js
new file mode 100644
index 00000000..a917c511
--- /dev/null
+++ b/test/ng/directive/ngSrcSpec.js
@@ -0,0 +1,17 @@
+'use strict';
+
+describe('ngSrc', function() {
+  var element;
+
+  afterEach(function() {
+    dealoc(element);
+  });
+
+  it('should not result empty string in img src', inject(function($rootScope, $compile) {
+    $rootScope.image = {};
+    element = $compile('<img ng-src="{{image.url}}">')($rootScope);
+    $rootScope.$digest();
+    expect(element.attr('src')).not.toBe('');
+    expect(element.attr('src')).toBe(undefined);
+  }));
+});