models: Make all fields default to None or empty collection

docs/changelog.rst

@@ -51,6 +51,10 @@ v0.20.0 (UNRELEASED)
   and in the other case explicitly set to the default value, but with otherwise
   equal fields. (Fixes: :issue:`837`)
 
+- Changed the default value of :attr:`mopidy.models.Album.num_tracks`,
+  :attr:`mopidy.models.Track.track_no`, and
+  :attr:`mopidy.models.Track.last_modified` from ``0`` to :class:`None`.
+
 
 v0.19.4 (2014-09-01)
 ====================

mopidy/models.py

@@ -241,7 +241,7 @@ class Album(ImmutableObject):
     :param artists: album artists
     :type artists: list of :class:`Artist`
     :param num_tracks: number of tracks in album
-    :type num_tracks: integer
+    :type num_tracks: integer or :class:`None` if unknown
     :param num_discs: number of discs in album
     :type num_discs: integer or :class:`None` if unknown
     :param date: album release date (YYYY or YYYY-MM-DD)
@@ -262,7 +262,7 @@ class Album(ImmutableObject):
     artists = frozenset()
 
     #: The number of tracks in the album. Read-only.
-    num_tracks = 0
+    num_tracks = None
 
     #: The number of discs in the album. Read-only.
     num_discs = None
@@ -302,7 +302,7 @@ class Track(ImmutableObject):
     :param genre: track genre
     :type genre: string
     :param track_no: track number in album
-    :type track_no: integer
+    :type track_no: integer or :class:`None` if unknown
     :param disc_no: disc number in album
     :type disc_no: integer or :class:`None` if unknown
     :param date: track release date (YYYY or YYYY-MM-DD)
@@ -316,7 +316,7 @@ class Track(ImmutableObject):
     :param musicbrainz_id: MusicBrainz ID
     :type musicbrainz_id: string
     :param last_modified: Represents last modification time
-    :type last_modified: integer
+    :type last_modified: integer or :class:`None` if unknown
     """
 
     #: The track URI. Read-only.
@@ -341,7 +341,7 @@ class Track(ImmutableObject):
     genre = None
 
     #: The track number in the album. Read-only.
-    track_no = 0
+    track_no = None
 
     #: The disc number in the album. Read-only.
     disc_no = None
@@ -364,7 +364,7 @@ class Track(ImmutableObject):
     #: Integer representing when the track was last modified, exact meaning
     #: depends on source of track. For local files this is the mtime, for other
     #: backends it could be a timestamp or simply a version counter.
-    last_modified = 0
+    last_modified = None
 
     def __init__(self, *args, **kwargs):
         get = lambda key: frozenset(kwargs.pop(key, None) or [])

mopidy/mpd/translator.py

@@ -44,11 +44,11 @@ def track_to_mpd_format(track, position=None):
     if track.date:
         result.append(('Date', track.date))
 
-    if track.album is not None and track.album.num_tracks != 0:
+    if track.album is not None and track.album.num_tracks is not None:
         result.append(('Track', '%d/%d' % (
-            track.track_no, track.album.num_tracks)))
+            track.track_no or 0, track.album.num_tracks)))
     else:
-        result.append(('Track', track.track_no))
+        result.append(('Track', track.track_no or 0))
     if position is not None and tlid is not None:
         result.append(('Pos', position))
         result.append(('Id', tlid))

tests/test_models.py

@@ -741,12 +741,6 @@ class TrackTest(unittest.TestCase):
         self.assertEqual(track1, track2)
         self.assertEqual(hash(track1), hash(track2))
 
-    def test_ignores_values_with_default_value_zero(self):
-        track1 = Track(name='name1')
-        track2 = Track(name='name1', track_no=0)
-        self.assertEqual(track1, track2)
-        self.assertEqual(hash(track1), hash(track2))
-
     def test_copy_can_reset_to_default_value(self):
         track1 = Track(name='name1')
         track2 = Track(name='name1', album=Album()).copy(album=None)