mpd: listplaylists should not return playlists without a name

docs/changes.rst

@@ -79,6 +79,9 @@ long time been our most requested feature. Finally, it's here!
 - The MPD commands ``search`` and ``find`` now allows the key ``file``, which
   is used by ncmpcpp instead of ``filename``.
 
+- The MPD command ``listplaylists`` will no longer return playlists without a
+  name. This could crash ncmpcpp.
+
 **MPRIS frontend**
 
 - The MPRIS playlists interface is now supported by our MPRIS frontend. This

mopidy/frontends/mpd/protocol/stored_playlists.py

@@ -70,9 +70,16 @@ def listplaylists(context):
         Last-Modified: 2010-02-06T02:10:25Z
         playlist: b
         Last-Modified: 2010-02-06T02:11:08Z
+
+    *Clarifications:*
+
+    - ncmpcpp 0.5.10 segfaults if we return 'playlist: ' on a line, so we must
+      ignore playlists without names, which isn't very useful anyway.
     """
     result = []
     for playlist in context.core.playlists.playlists.get():
+        if not playlist.name:
+            continue
         result.append(('playlist', playlist.name))
         last_modified = (
             playlist.last_modified or dt.datetime.now()).isoformat()

tests/frontends/mpd/protocol/stored_playlists_test.py

@@ -64,6 +64,15 @@ class PlaylistsHandlerTest(protocol.BaseTestCase):
         self.assertInResponse('Last-Modified: 2001-03-17T13:41:17Z')
         self.assertInResponse('OK')
 
+    def test_listplaylists_ignores_playlists_without_name(self):
+        last_modified = datetime.datetime(2001, 3, 17, 13, 41, 17, 12345)
+        self.backend.playlists.playlists = [
+            Playlist(name='', last_modified=last_modified)]
+
+        self.sendRequest('listplaylists')
+        self.assertNotInResponse('playlist: ')
+        self.assertInResponse('OK')
+
     def test_load_known_playlist_appends_to_tracklist(self):
         self.core.tracklist.add([Track(uri='a'), Track(uri='b')])
         self.assertEqual(len(self.core.tracklist.tracks.get()), 2)