core: Let tracklist.add() lookup tracks by URI

docs/changes.rst

@@ -24,6 +24,12 @@ v0.13.0 (in development)
   the Mopidy process will now always make it log tracebacks for all alive
   threads.
 
+- :meth:`mopidy.core.TracklistController.add` now accepts an ``uri`` which it
+  will lookup in the libraries and then add to the tracklist. This is helpful
+  for e.g. web clients that doesn't want to transfer all track meta data back
+  to the server just to add it to the tracklist when the server already got all
+  the needed information easily available. (Fixes: :issue:`325`)
+
 **Audio sub-system**
 
 - Make audio error logging handle log messages with non-ASCII chars. (Fixes:

mopidy/core/tracklist.py

@@ -62,10 +62,13 @@ class TracklistController(object):
     Is not reset before Mopidy is restarted.
     """
 
-    def add(self, tracks, at_position=None):
+    def add(self, tracks=None, at_position=None, uri=None):
         """
         Add the track or list of tracks to the tracklist.
 
+        If ``uri`` is given instead of ``tracks``, the URI is looked up in the
+        library and the resulting tracks are added to the tracklist.
+
         If ``at_position`` is given, the tracks placed at the given position in
         the tracklist. If ``at_position`` is not given, the tracks are appended
         to the end of the tracklist.
@@ -76,9 +79,18 @@ class TracklistController(object):
         :type tracks: list of :class:`mopidy.models.Track`
         :param at_position: position in tracklist to add track
         :type at_position: int or :class:`None`
+        :param uri: URI for tracks to add
+        :type uri: string
         :rtype: list of :class:`mopidy.models.TlTrack`
         """
+        assert tracks is not None or uri is not None, \
+            'tracks or uri must be provided'
+
+        if tracks is None and uri is not None:
+            tracks = self._core.library.lookup(uri)
+
         tl_tracks = []
+
         for track in tracks:
             tl_track = TlTrack(self._next_tlid, track)
             self._next_tlid += 1

tests/core/tracklist_test.py

@@ -1,5 +1,8 @@
 from __future__ import unicode_literals
 
+import mock
+
+from mopidy.backends import base
 from mopidy.core import Core
 from mopidy.models import Track
 
@@ -9,13 +12,31 @@ from tests import unittest
 class TracklistTest(unittest.TestCase):
     def setUp(self):
         self.tracks = [
-            Track(uri='a', name='foo'),
-            Track(uri='b', name='foo'),
-            Track(uri='c', name='bar')
+            Track(uri='dummy1:a', name='foo'),
+            Track(uri='dummy1:b', name='foo'),
+            Track(uri='dummy1:c', name='bar'),
         ]
-        self.core = Core(audio=None, backends=[])
+
+        self.backend = mock.Mock()
+        self.backend.uri_schemes.get.return_value = ['dummy1']
+        self.library = mock.Mock(spec=base.BaseLibraryProvider)
+        self.backend.library = self.library
+
+        self.core = Core(audio=None, backends=[self.backend])
         self.tl_tracks = self.core.tracklist.add(self.tracks)
 
+    def test_add_by_uri_looks_up_uri_in_library(self):
+        track = Track(uri='dummy1:x', name='x')
+        self.library.lookup().get.return_value = [track]
+        self.library.lookup.reset_mock()
+
+        tl_tracks = self.core.tracklist.add(uri='dummy1:x')
+
+        self.library.lookup.assert_called_once_with('dummy1:x')
+        self.assertEqual(1, len(tl_tracks))
+        self.assertEqual(track, tl_tracks[0].track)
+        self.assertEqual(tl_tracks, self.core.tracklist.tl_tracks[-1:])
+
     def test_remove_removes_tl_tracks_matching_query(self):
         tl_tracks = self.core.tracklist.remove(name='foo')