Merge pull request #18 from rraval/master

Implement jQuery compatible `.pipe()`

deferred.coffee

@@ -80,20 +80,24 @@ Deferred = ->
     # It also makes sense to set up a piper to which can filter the success or failure arguments through the given filter methods.
     # Quite useful if you want to transform the results of a promise or log them in some way.
     pipe = (doneFilter, failFilter) ->
-      deferred = new Deferred()
-      filter = (source, destination, filter) ->
-        if filter then candidate[source] (args...) ->
-          filteredArgs = filter args...
-          # Some pipes might want to return another promise, though, so let's check if the object is a promise and resolve it correctly if it is.
-          if isPromise filteredArgs
-            filteredArgs[source] (args...) -> destination args...
-          # Otherwise we can just send the filtered values onward.
-          else destination(filteredArgs)
-        # If no filters have been passed, this degenerates into a shortcut method for adding both `done` and `fail` callbacks.
-        else candidate[source] (args...) -> destination args...
-      filter 'done', deferred.resolve, doneFilter
-      filter 'fail', deferred.reject, failFilter
-      deferred
+      master = new Deferred()
+
+      filter = (source, funnel, callback) ->
+        if callback?
+          candidate[source]((args...) ->
+            value = callback(args...)
+            if isPromise(value)
+              value.done(master.resolve).fail(master.reject)
+            else
+              master[funnel](value)
+          )
+        else
+          candidate[source](master[funnel])
+
+      filter('done', 'resolve', doneFilter)
+      filter('fail', 'reject', failFilter)
+
+      return master
 
     # Expose the `.pipe(doneFilter, failFilter)` method and alias it to `.then()`.
     candidate.pipe = pipe
@@ -133,6 +137,10 @@ Deferred = ->
 # Let's set up a `.when([deferreds])` method to do that. It should be able to take any number or deferreds as arguments (or an array of them).
 _when = ->
   defs = flatten arguments
+  if defs.length == 1
+    # small optimization: pass a single deferred object along
+    return if isPromise defs[0] then defs[0] else (new Deferred()).resolve(defs[0]).promise()
+
   trigger = new Deferred()
   return trigger.resolve().promise() if not defs.length
 

deferred_test.coffee

@@ -177,6 +177,18 @@ describe 'deferred', ->
 
       def.resolve('r1')
 
+    it 'should allow changing the state', (done) ->
+      def = deferred.Deferred()
+
+      def.pipe((result) ->
+        return deferred.Deferred().reject('failure').promise()
+      ).fail((msg) ->
+        assert.equal msg, 'failure'
+        done() if msg is 'failure'
+      )
+
+      def.resolve('r1')
+
   describe 'then', ->
     it 'should alias pipe', ->
       def = new deferred.Deferred()
@@ -247,6 +259,7 @@ describe 'deferred', ->
       it 'should pass on resolve arguments as is when used with a single deferred', (done) ->
         d1 = new deferred.Deferred()
         after_all = deferred.when(d1)
+        assert.equal d1, after_all
         after_all.done (arg1) -> done() if arg1 is 42
         d1.resolve(42)