fix "beet modify" for date fields (GC-449)

This is fixed by allowing MediaFiles to convert strings to integers on
assignment. An eventual complete fix will perform these type conversions in the
Item interface.

beets/mediafile.py

@@ -255,7 +255,7 @@ class Packed(object):
             field_lengths = [4, 2, 2] # YYYY-MM-DD
             elems = []
             for i, item in enumerate(new_items):
-                elems.append( ('%0' + str(field_lengths[i]) + 'i') % item )
+                elems.append('{0:0{1}}'.format(int(item), field_lengths[i]))
             self.items = '-'.join(elems)
         elif self.packstyle == packing.TUPLE:
             self.items = new_items

beets/util/__init__.py

@@ -529,7 +529,7 @@ def cpu_count():
     """Return the number of hardware thread contexts (cores or SMT
     threads) in the system.
     """
-    # Adapted from observing the soundconverter project:
+    # Adapted from the soundconverter project:
     # https://github.com/kassoulet/soundconverter
     if sys.platform == 'win32':
         try:

docs/changelog.rst

@@ -51,6 +51,8 @@ Changelog
   modify files' tags even when they successfully change the database.
 * Fix a VFS bug leading to a crash in the :doc:`/plugins/bpd` when files had
   non-ASCII extensions.
+* Fix for changing date fields (like "year") with the :ref:`modify-cmd`
+  command.
 * Add a human-readable error message when writing files' tags fails.
 * Changed plugin loading so that modules can be imported without
   unintentionally loading the plugins they contain.

docs/reference/cli.rst

@@ -164,6 +164,8 @@ You'll be shown a list of the files that will be removed and asked to confirm.
 By default, this just removes entries from the library database; it doesn't
 touch the files on disk. To actually delete the files, use ``beet remove -d``.
 
+.. _modify-cmd:
+
 modify
 ``````
 ::

test/test_mediafile.py

@@ -196,6 +196,15 @@ class MissingAudioDataTest(unittest.TestCase):
         del self.mf.mgfile.info.bitrate # Not available directly.
         self.assertEqual(self.mf.bitrate, 0)
 
+class TypeTest(unittest.TestCase):
+    def setUp(self):
+        path = os.path.join(_common.RSRC, 'full.mp3')
+        self.mf = beets.mediafile.MediaFile(path)
+
+    def test_year_integer_in_string(self):
+        self.mf.year = '2009'
+        self.assertEqual(self.mf.year, 2009)
+
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)