feat(attr-interpolate): add attribute interpolation.

Author: mhevery

lib/directives/ng_mustache.dart

@@ -4,10 +4,9 @@ class NgTextMustacheDirective {
   static String $selector = r':contains(/{{.*}}/)';
 
   dom.Node element;
-  DirectiveValue value;
   ParsedFn interpolateFn;
 
-  NgTextMustacheDirective(dom.Node this.element, DirectiveValue this.value, Interpolate interpolate) {
+  NgTextMustacheDirective(dom.Node this.element, DirectiveValue value, Interpolate interpolate) {
     interpolateFn = interpolate(value.value);
     element.text = '';
   }
@@ -19,8 +18,21 @@ class NgTextMustacheDirective {
 
 class NgAttrMustacheDirective {
   static String $selector = r'[*=/{{.*}}/]';
+  static RegExp ATTR_NAME_VALUE_REGEXP = new RegExp(r'^([^=]+)=(.*)$');
 
-  attach(Scope scope) {
+  ParsedFn interpolateFn;
+  dom.Element element;
+  Function attrSetter;
 
+  NgAttrMustacheDirective(dom.Element this.element, DirectiveValue value, Interpolate interpolate) {
+    var match = ATTR_NAME_VALUE_REGEXP.firstMatch(value.value);
+    var attrName = match[1];
+    interpolateFn = interpolate(match[2]);
+    attrSetter = (text) => element.attributes[attrName] = text;
+    attrSetter('');
+  }
+
+  attach(Scope scope) {
+    scope.$watch(interpolateFn, attrSetter);
   }
 }

test/_specs.dart

@@ -133,6 +133,7 @@ class JQuery implements List<Node> {
   toString() => fold('', (html, node) => '$html${_toHtml(node, true)}');
   eq(num childIndex) => $(this[childIndex]);
   remove() => forEach((n) => n.remove());
+  attr([String name]) => accessor((n) => n.attributes[name], (n, v) => n.attributes[name] = v);
 }
 
 class Logger implements List {

test/directives/ng_mustache_spec.dart

@@ -19,5 +19,22 @@ main() {
       $rootScope.$digest();
       expect(element.text()).toEqual('OK!');
     }));
+
+
+    it('should replace {{}} in attribute', inject((Compiler $compile, Scope $rootScope) {
+      var element = $('<div some-attr="{{name}}"></div>');
+      var template = $compile(element);
+
+      $rootScope.name = 'OK';
+      var block = template();
+
+      element = $(block.elements);
+
+      block.attach($rootScope);
+
+      expect(element.attr('some-attr')).toEqual('');
+      $rootScope.$digest();
+      expect(element.attr('some-attr')).toEqual('OK');
+    }));
   });
 }