feat(ngSrcset): add new ngSrcset directive

In line with ngSrc and ngHref, this new directive ensures that the
`srcset` HTML5 attribute does not include a pre-interpolated string.
Without it the browser will fetch from the URL with the literal text
`{{hash}}` until AngularJS replaces the expression inside `{{hash}}`.

Closes #2601

1 files changed, 27 insertions, 2 deletions

diff --git a/src/ng/directive/booleanAttrs.js b/src/ng/directive/booleanAttrs.js
index 7e0e3a42..8f7399a6 100644
--- a/src/ng/directive/booleanAttrs.js
+++ b/src/ng/directive/booleanAttrs.js
@@ -107,6 +107,31 @@
 
 /**
  * @ngdoc directive
+ * @name ng.directive:ngSrcset
+ * @restrict A
+ *
+ * @description
+ * Using Angular markup like `{{hash}}` in a `srcset` attribute doesn't
+ * work right: The browser will fetch from the URL with the literal
+ * text `{{hash}}` until Angular replaces the expression inside
+ * `{{hash}}`. The `ngSrcset` directive solves this problem.
+ *
+ * The buggy way to write it:
+ * <pre>
+ * <img srcset="http://www.gravatar.com/avatar/{{hash}} 2x"/>
+ * </pre>
+ *
+ * The correct way to write it:
+ * <pre>
+ * <img ng-srcset="http://www.gravatar.com/avatar/{{hash}} 2x"/>
+ * </pre>
+ *
+ * @element IMG
+ * @param {template} ngSrcset any string which can contain `{{}}` markup.
+ */
+
+/**
+ * @ngdoc directive
  * @name ng.directive:ngDisabled
  * @restrict A
  *
@@ -325,8 +350,8 @@ forEach(BOOLEAN_ATTR, function(propName, attrName) {
 });
 
 
-// ng-src, ng-href are interpolated
-forEach(['src', 'href'], function(attrName) {
+// ng-src, ng-srcset, ng-href are interpolated
+forEach(['src', 'srcset', 'href'], function(attrName) {
   var normalized = directiveNormalize('ng-' + attrName);
   ngAttributeAliasDirectives[normalized] = function() {
     return {