core: library.refresh() should check if backend has library

...and not playlists.

Fixes #1257

docs/changelog.rst

@@ -10,6 +10,10 @@ v1.1.1 (UNRELEASED)
 
 Bug fix release.
 
+- Core: Make :meth:`mopidy.core.LibraryController.refresh` work for all
+  backends with a library provider. Previously, it wrongly worked for all
+  backends with a playlists provider. (Fixes: :issue:`1257`)
+
 - Stream: If "file" is present in the :confval:`stream/protocols` config value
   and the :ref:`ext-file` extension is enabled, we exited with an error because
   two extensions claimed the same URI scheme. We now log a warning recommending

mopidy/core/library.py

@@ -255,7 +255,7 @@ class LibraryController(object):
         backends = {}
         uri_scheme = urlparse.urlparse(uri).scheme if uri else None
 
-        for backend_scheme, backend in self.backends.with_playlists.items():
+        for backend_scheme, backend in self.backends.with_library.items():
             backends.setdefault(backend, set()).add(backend_scheme)
 
         for backend, backend_schemes in backends.items():

tests/core/test_library.py

@@ -20,6 +20,7 @@ class BaseCoreLibraryTest(unittest.TestCase):
         self.library1.get_images.return_value.get.return_value = {}
         self.library1.root_directory.get.return_value = dummy1_root
         self.backend1.library = self.library1
+        self.backend1.has_playlists.return_value.get.return_value = False
 
         dummy2_root = Ref.directory(uri='dummy2:directory', name='dummy2')
         self.backend2 = mock.Mock()
@@ -29,13 +30,14 @@ class BaseCoreLibraryTest(unittest.TestCase):
         self.library2.get_images.return_value.get.return_value = {}
         self.library2.root_directory.get.return_value = dummy2_root
         self.backend2.library = self.library2
+        self.backend2.has_playlists.return_value.get.return_value = False
 
         # A backend without the optional library provider
         self.backend3 = mock.Mock()
         self.backend3.uri_schemes.get.return_value = ['dummy3']
         self.backend3.actor_ref.actor_class.__name__ = 'DummyBackend3'
-        self.backend3.has_library().get.return_value = False
-        self.backend3.has_library_browse().get.return_value = False
+        self.backend3.has_library.return_value.get.return_value = False
+        self.backend3.has_library_browse.return_value.get.return_value = False
 
         self.core = core.Core(mixer=None, backends=[
             self.backend1, self.backend2, self.backend3])