local: Add ROOT_DIRECTORY_URI constant

Related to #833

docs/changelog.rst

@@ -28,6 +28,10 @@ Bug fix release.
   and docs to match how the core use the backend's browse method. (Fixes:
   :issue:`833`)
 
+- Local library API: Add :attr:`mopidy.local.ROOT_DIRECTORY_URI` constant for
+  use by implementors of :method:`mopidy.local.Library.browse`. (Related to:
+  :issue:`833`)
+
 
 v0.19.3 (2014-08-03)
 ====================

mopidy/local/__init__.py

@@ -46,6 +46,15 @@ class Extension(ext.Extension):
         return LocalCommand()
 
 
+ROOT_DIRECTORY_URI = 'local:directory'
+"""
+URI of the local backend's root directory.
+
+This constant should be used by libraries implementing the
+:meth:`Library.browse` method.
+"""
+
+
 class Library(object):
     """
     Local library interface.
@@ -68,6 +77,9 @@ class Library(object):
         """
         Browse directories and tracks at the given URI.
 
+        The URI for the root directory is a constant available at
+        :attr:`ROOT_DIRECTORY_URI`.
+
         :param string path: URI to browse.
         :rtype: List of :class:`~mopidy.models.Ref` tracks and directories.
         """

mopidy/local/json.py

@@ -61,8 +61,7 @@ class _BrowseCache(object):
     splitpath_re = re.compile(r'([^/]+)')
 
     def __init__(self, uris):
-        # TODO: local.ROOT_DIRECTORY_URI
-        self._cache = {'local:directory': collections.OrderedDict()}
+        self._cache = {local.ROOT_DIRECTORY_URI: collections.OrderedDict()}
 
         for track_uri in uris:
             path = translator.local_track_uri_to_path(track_uri, b'/')
@@ -97,10 +96,10 @@ class _BrowseCache(object):
             else:
                 # Loop completed, so final child needs to be added to root.
                 if child:
-                    self._cache['local:directory'][child.uri] = child
+                    self._cache[local.ROOT_DIRECTORY_URI][child.uri] = child
                 # If no parent was set we belong in the root.
                 if not parent_uri:
-                    parent_uri = 'local:directory'
+                    parent_uri = local.ROOT_DIRECTORY_URI
 
             self._cache[parent_uri][track_uri] = track_ref
 

mopidy/local/library.py

@@ -2,7 +2,7 @@ from __future__ import unicode_literals
 
 import logging
 
-from mopidy import backend, models
+from mopidy import backend, local, models
 
 logger = logging.getLogger(__name__)
 
@@ -10,8 +10,8 @@ logger = logging.getLogger(__name__)
 class LocalLibraryProvider(backend.LibraryProvider):
     """Proxy library that delegates work to our active local library."""
 
-    root_directory = models.Ref.directory(uri=b'local:directory',
-                                          name='Local media')
+    root_directory = models.Ref.directory(
+        uri=local.ROOT_DIRECTORY_URI, name='Local media')
 
     def __init__(self, backend, library):
         super(LocalLibraryProvider, self).__init__(backend)