db: Give the Tagger a function for untagging Tracks

This is used to remove a Track from each of its Playlists before
deleting.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/db/tagger.py

@@ -262,3 +262,17 @@ class Thread(threading.Thread):
             self._mtime = mtime
             self._tags = None
             self._condition.notify()
+
+
+def untag_track(db: GObject.TYPE_PYOBJECT, track: tracks.Track) -> None:
+    """Untag a Track."""
+    medium = track.get_medium()
+    year = track.get_year()
+
+    playlists = [plist for plist in db.playlists.store]
+    playlists.extend([medium, medium.get_album()])
+    playlists.extend(track.get_artists())
+    playlists.extend([year, year.parent, track.get_library()])
+
+    for plist in playlists:
+        plist.remove_track(track)

tests/db/test_tagger.py

@@ -400,3 +400,37 @@ class TestTaggerThread(tests.util.TestCase):
                               emmental.db.connection.Connection)
         self.assertEqual(audio_tags.artists[0].name, "Some Artist")
         self.assertEqual(audio_tags.artists[1].name, "Some Artist")
+
+
+class TestUntag(tests.util.TestCase):
+    """Test untagging a Track."""
+
+    def setUp(self):
+        """Set up common variables."""
+        super().setUp()
+        self.sql.playlists.load(now=True)
+
+        self.file = pathlib.Path("/a/b/c.ogg")
+        self.library = self.sql.libraries.create(self.file.parent)
+        self.raw_tags = {"album": ["Album Name"],
+                         "artist": ["Track Artist"],
+                         "date": ["1988-06"],
+                         "title": ["Test Title"],
+                         "tracknumber": ["3"],
+                         "musicbrainz_releasetrackid": ["ab-cd-ef"]}
+        self.audio_tags = emmental.audio.tagger._Tags(self.file, self.raw_tags,
+                                                      12345, 678.9)
+        self.tagged = emmental.db.tagger.Tags(self.sql, self.audio_tags,
+                                              self.library)
+
+        for tbl in self.sql.playlist_tables():
+            tbl.queue.complete()
+
+    def test_untag_track(self):
+        """Test untagging a Track before deleting."""
+        emmental.db.tagger.untag_track(self.sql, self.tagged.track)
+
+        for tbl in self.sql.playlist_tables():
+            for plist in tbl.store:
+                with self.subTest(table=tbl, playlist=plist.name):
+                    self.assertFalse(plist.has_track(self.tagged.track))