Enhance the apis and add more tests

lib/observer.js

@@ -58,17 +58,36 @@ ObserverMixin.clearObservers = function(operation) {
 };
 
 /**
- * Invoke all async observers for the given operation.
- * @param {String} operation The operation name.
+ * Invoke all async observers for the given operation(s).
+ * @param {String|String[]} operation The operation name(s).
  * @param {Object} context Operation-specific context.
  * @param {function(Error=)} callback The callback to call when all observers
  *   has finished.
  */
 ObserverMixin.notifyObserversOf = function(operation, context, callback) {
-  var observers = this._observers && this._observers[operation];
-
+  var self = this;
   if (!callback) callback = utils.createPromiseCallback();
 
+  function createNotifier(op) {
+    return function(ctx, done) {
+      if (typeof ctx === 'function' && done === undefined) {
+        done = ctx;
+        ctx = context;
+      }
+      self.notifyObserversOf(op, context, done);
+    };
+  }
+
+  if (Array.isArray(operation)) {
+    var tasks = [];
+    for (var i = 0, n = operation.length; i < n; i++) {
+      tasks.push(createNotifier(operation[i]));
+    }
+    return async.waterfall(tasks, callback);
+  }
+
+  var observers = this._observers && this._observers[operation];
+
   this._notifyBaseObservers(operation, context, function doNotify(err) {
     if (err) return callback(err, context);
     if (!observers || !observers.length) return callback(null, context);
@@ -115,21 +134,34 @@ ObserverMixin._notifyBaseObservers = function(operation, context, callback) {
  */
 ObserverMixin.notifyObserversAround = function(operation, context, fn, callback) {
   var self = this;
+  context = context || {};
+  // Add callback to the context object so that an observer can skip other
+  // ones by calling the callback function directly and not calling next
+  if (context.end === undefined) {
+    context.end = callback;
+  }
+  // First notify before observers
   return self.notifyObserversOf('before ' + operation, context,
     function(err, context) {
-      if (err) return callback(err, context);
+      if (err) return callback(err);
 
       function cbForWork(err) {
-        if (err) return callback(err, context);
-        var returnedArgs = [].slice.call(arguments, 1);
+        var args = [].slice.call(arguments, 0);
+        if (err) return callback.apply(null, args);
+        // Find the list of params from the callback in addition to err
+        var returnedArgs = args.slice(1);
+        // Set up the array of results
         context.results = returnedArgs;
+        // Notify after observers
         self.notifyObserversOf('after ' + operation, context,
           function(err, context) {
             if (err) return callback(err, context);
             var results = returnedArgs;
-            if (context) {
+            if (context && Array.isArray(context.results)) {
+              // Pickup the results from context
               results = context.results;
             }
+            // Build the list of params for final callback
             var args = [err].concat(results);
             callback.apply(null, args);
           });

test/async-observer.test.js

@@ -37,6 +37,18 @@ describe('async observer', function() {
     });
   });
 
+  it('allows multiple operations to be notified in one call', function(done) {
+    var notifications = [];
+    TestModel.observe('event1', pushAndNext(notifications, 'one'));
+    TestModel.observe('event2', pushAndNext(notifications, 'two'));
+
+    TestModel.notifyObserversOf(['event1', 'event2'], {}, function(err) {
+      if (err) return done(err);
+      notifications.should.eql(['one', 'two']);
+      done();
+    });
+  });
+
   it('inherits observers from base model', function(done) {
     var notifications = [];
     TestModel.observe('event', pushAndNext(notifications, 'base'));
@@ -51,6 +63,22 @@ describe('async observer', function() {
     });
   });
 
+  it('allow multiple operations to be notified with base models', function(done) {
+    var notifications = [];
+    TestModel.observe('event1', pushAndNext(notifications, 'base1'));
+    TestModel.observe('event2', pushAndNext(notifications, 'base2'));
+
+    var Child = TestModel.extend('Child');
+    Child.observe('event1', pushAndNext(notifications, 'child1'));
+    Child.observe('event2', pushAndNext(notifications, 'child2'));
+
+    Child.notifyObserversOf(['event1', 'event2'], {}, function(err) {
+      if (err) return done(err);
+      notifications.should.eql(['base1', 'child1', 'base2', 'child2']);
+      done();
+    });
+  });
+
   it('does not modify observers in the base model', function(done) {
     var notifications = [];
     TestModel.observe('event', pushAndNext(notifications, 'base'));
@@ -194,6 +222,57 @@ describe('async observer', function() {
             done();
           });
       });
+
+    it('should allow observers to skip other ones',
+      function(done) {
+        TestModel.observe('before invoke',
+          function(context, next) {
+            notifications.push('before invoke');
+            context.end(null, 0);
+          });
+        TestModel.observe('after invoke',
+          pushAndNext(notifications, 'after invoke'));
+
+        var context = {};
+
+        function work(done) {
+          process.nextTick(function() {
+            done(null, 1, 2);
+          });
+        }
+
+        TestModel.notifyObserversAround('invoke', context, work,
+          function(err, r1) {
+            r1.should.eql(0);
+            notifications.should.eql(['before invoke']);
+            done();
+          });
+      });
+
+    it('should allow observers to tweak results',
+      function(done) {
+        TestModel.observe('after invoke',
+          function(context, next) {
+            notifications.push('after invoke');
+            context.results = [3];
+            next();
+          });
+
+        var context = {};
+
+        function work(done) {
+          process.nextTick(function() {
+            done(null, 1, 2);
+          });
+        }
+
+        TestModel.notifyObserversAround('invoke', context, work,
+          function(err, r1) {
+            r1.should.eql(3);
+            notifications.should.eql(['after invoke']);
+            done();
+          });
+      });
   });
 
   it('resolves promises returned by observers', function(done) {