Fix plchanges so it returns nothing when nothing has changed

docs/changes.rst

@@ -75,6 +75,9 @@ backends:
 - :issue:`218`: The MPD commands ``listplaylist`` and ``listplaylistinfo`` now
   accepts unquotes playlist names if they don't contain spaces.
 
+- The MPD command ``plchanges`` always returned the entire playlist. It now
+  returns an empty response when the client has seen the latest version.
+
 
 v0.8.1 (2012-10-30)
 ===================

mopidy/frontends/mpd/protocol/current_playlist.py

@@ -307,7 +307,7 @@ def plchanges(context, version):
     - Calls ``plchanges "-1"`` two times per second to get the entire playlist.
     """
     # XXX Naive implementation that returns all tracks as changed
-    if int(version) < context.core.current_playlist.version:
+    if int(version) < context.core.current_playlist.version.get():
         return translator.tracks_to_mpd_format(
             context.core.current_playlist.cp_tracks.get())
 

tests/frontends/mpd/protocol/current_playlist_test.py

@@ -364,7 +364,7 @@ class CurrentPlaylistHandlerTest(protocol.BaseTestCase):
         self.sendRequest(u'playlistsearch any "needle"')
         self.assertEqualResponse(u'ACK [0@0] {} Not implemented')
 
-    def test_plchanges(self):
+    def test_plchanges_with_lower_version_returns_changes(self):
         self.core.current_playlist.append(
             [Track(name='a'), Track(name='b'), Track(name='c')])
 
@@ -374,6 +374,28 @@ class CurrentPlaylistHandlerTest(protocol.BaseTestCase):
         self.assertInResponse(u'Title: c')
         self.assertInResponse(u'OK')
 
+    def test_plchanges_with_equal_version_returns_nothing(self):
+        self.core.current_playlist.append(
+            [Track(name='a'), Track(name='b'), Track(name='c')])
+
+        self.assertEqual(self.core.current_playlist.version.get(), 1)
+        self.sendRequest(u'plchanges "1"')
+        self.assertNotInResponse(u'Title: a')
+        self.assertNotInResponse(u'Title: b')
+        self.assertNotInResponse(u'Title: c')
+        self.assertInResponse(u'OK')
+
+    def test_plchanges_with_greater_version_returns_nothing(self):
+        self.core.current_playlist.append(
+            [Track(name='a'), Track(name='b'), Track(name='c')])
+
+        self.assertEqual(self.core.current_playlist.version.get(), 1)
+        self.sendRequest(u'plchanges "2"')
+        self.assertNotInResponse(u'Title: a')
+        self.assertNotInResponse(u'Title: b')
+        self.assertNotInResponse(u'Title: c')
+        self.assertInResponse(u'OK')
+
     def test_plchanges_with_minus_one_returns_entire_playlist(self):
         self.core.current_playlist.append(
             [Track(name='a'), Track(name='b'), Track(name='c')])