fix($compile): have $observe return registration function

src/ng/compile.js

@@ -139,6 +139,14 @@
  */
 
 
+/**
+ * @ngdoc service
+ * @name angular.module.ng.$compileProvider
+ * @function
+ *
+ * @description
+ *
+ */
 $CompileProvider.$inject = ['$provide'];
 function $CompileProvider($provide) {
   var hasDirectives = {},
@@ -148,7 +156,21 @@ function $CompileProvider($provide) {
       MULTI_ROOT_TEMPLATE_ERROR = 'Template must have exactly one root element. was: ';
 
 
-  this.directive = function registerDirective(name, directiveFactory) {
+  /**
+   * @ngdoc function
+   * @name angular.module.ng.$compileProvider.directive
+   * @methodOf angular.module.ng.$compileProvider
+   * @function
+   *
+   * @description
+   * Register directives with the compiler.
+   *
+   * @param {string} name Name of the directive in camel-case. (ie <code>ngBind</code> which will match as
+   *                <code>ng-bind</code>).
+   * @param {function} directiveFactory An injectable directive factroy function. See {@link guide/directive} for more
+   *                info.
+   */
+   this.directive = function registerDirective(name, directiveFactory) {
     if (isString(name)) {
       assertArg(directiveFactory, 'directive');
       if (!hasDirectives.hasOwnProperty(name)) {
@@ -295,12 +317,14 @@ function $CompileProvider($provide) {
        *
        * @param {string} key Normalized key. (ie ngAttribute) .
        * @param {function(*)} fn Function that will be called whenever the attribute value changes.
+       * @returns {function(*)} the `fn` Function passed in.
        */
       $observe: function(key, fn) {
         // keep only observers for interpolated attrs
         if (this.$$observers[key]) {
           this.$$observers[key].push(fn);
         }
+        return fn;
       }
     };
 

test/ng/compileSpec.js

@@ -1255,7 +1255,7 @@ describe('$compile', function() {
         return function(scope, elm, attr) {
           observeSpy = jasmine.createSpy('$observe attr');
 
-          attr.$observe('someAttr', observeSpy);
+          expect(attr.$observe('someAttr', observeSpy)).toBe(observeSpy);
           attrValueDuringLinking = attr.someAttr;
         };
       });