PICARD-3229: Fix tracknum_and_title_from_filename raising IndexError

tracknum_and_title_from_filename would raise for filenames consisting
only of a track number longer then one digit.

Author: phw

picard/util/__init__.py

@@ -646,10 +646,11 @@ def tracknum_and_title_from_filename(base_filename):
         tracknumber = str(tracknumber)
         stripped_filename = filename.lstrip('0')
         tnlen = len(tracknumber)
-        if stripped_filename[:tnlen] == tracknumber and len(stripped_filename) > 1:
-            # Strip the dot in front of the tracknumber, if present
-            dot_offset = 1 if stripped_filename[tnlen:][0] == '.' else 0
-            title = stripped_filename[tnlen + dot_offset:].lstrip()
+        if stripped_filename[:tnlen] == tracknumber:
+            # Strip track number from title
+            title = stripped_filename[tnlen:]
+            # Strip the dot after the tracknumber, if present
+            title = title.lstrip('.').lstrip()
 
     return GuessedFromFilename(tracknumber, title)
 

test/test_utils.py

@@ -674,7 +674,11 @@ class TracknumAndTitleFromFilenameTest(PicardTestCase):
     def test_returns_expected_tracknumber(self):
         tests = (
             ((None, 'Foo'), 'Foo.mp3'),
-            (('1', '1'), '1.opus'),
+            ((None, '0'), '0.opus'),
+            ((None, '0000'), '0000.opus'),
+            (('1', ''), '1.opus'),
+            (('12', ''), '12.opus'),
+            (('12', ''), '012.opus'),
             (('1', 'Track 0001'), 'Track 0001.mp3'),
             (('42', 'Track-42'), 'Track-42.mp3'),
             (('99', 'Foo'), '99 Foo.mp3'),