Refactor MetadataSourcePlugin._get_id()

and put to use in Spotify plugin.

- Make _get_id() a staticmethod usable from outside a metadata source plugin.
- id_regex now has to be passed as an argument instead of assuming it is
  accessible via an instance variable (self.id_regex).
- In the Spotify plugin, import spotify_id_regex from util.id_extractors

beets/plugins.py

@@ -705,22 +705,27 @@ class MetadataSourcePlugin(metaclass=abc.ABCMeta):
 
         return artist_string, artist_id
 
-    def _get_id(self, url_type, id_):
+    @staticmethod
+    def _get_id(url_type, id_, id_regex):
         """Parse an ID from its URL if necessary.
 
         :param url_type: Type of URL. Either 'album' or 'track'.
         :type url_type: str
         :param id_: Album/track ID or URL.
         :type id_: str
+        :param id_regex: A dictionary containing a regular expression
+            extracting an ID from an URL (if it's not an ID already) in
+            'pattern' and the number of the match group in 'match_group'.
+        :type id_regex: dict
         :return: Album/track ID.
         :rtype: str
         """
-        self._log.debug(
-            "Searching {} for {} '{}'", self.data_source, url_type, id_
+        log.debug(
+            "Extracting {} ID from '{}'", url_type, id_
         )
-        match = re.search(self.id_regex['pattern'].format(url_type), str(id_))
+        match = re.search(id_regex['pattern'].format(url_type), str(id_))
         if match:
-            id_ = match.group(self.id_regex['match_group'])
+            id_ = match.group(id_regex['match_group'])
             if id_:
                 return id_
         return None

beetsplug/spotify.py

@@ -32,6 +32,7 @@ from beets.autotag.hooks import AlbumInfo, TrackInfo
 from beets.dbcore import types
 from beets.library import DateType
 from beets.plugins import BeetsPlugin, MetadataSourcePlugin
+from beets.util.id_extractors import spotify_id_regex
 
 DEFAULT_WAITING_TIME = 5
 
@@ -69,12 +70,7 @@ class SpotifyPlugin(MetadataSourcePlugin, BeetsPlugin):
     track_url = 'https://api.spotify.com/v1/tracks/'
     audio_features_url = 'https://api.spotify.com/v1/audio-features/'
 
-    # Spotify IDs consist of 22 alphanumeric characters
-    # (zero-left-padded base62 representation of randomly generated UUID4)
-    id_regex = {
-        'pattern': r'(^|open\.spotify\.com/{}/)([0-9A-Za-z]{{22}})',
-        'match_group': 2,
-    }
+    id_regex = spotify_id_regex
 
     spotify_audio_features = {
         'acousticness': 'spotify_acousticness',
@@ -216,7 +212,7 @@ class SpotifyPlugin(MetadataSourcePlugin, BeetsPlugin):
         :return: AlbumInfo object for album
         :rtype: beets.autotag.hooks.AlbumInfo or None
         """
-        spotify_id = self._get_id('album', album_id)
+        spotify_id = self._get_id('album', album_id, self.id_regex)
         if spotify_id is None:
             return None
 
@@ -330,7 +326,7 @@ class SpotifyPlugin(MetadataSourcePlugin, BeetsPlugin):
         :rtype: beets.autotag.hooks.TrackInfo or None
         """
         if track_data is None:
-            spotify_id = self._get_id('track', track_id)
+            spotify_id = self._get_id('track', track_id, self.id_regex)
             if spotify_id is None:
                 return None
             track_data = self._handle_response(