zero plugin zeroes disctotal if single disc (#6306)

When `omit_single_disc` is set, `disctotal` is now also zeroed alongside
`disc`. These tags work together ("Disc 2 of 3") so keeping one without
the other is inconsistent.

Previously, only the `disc` tag was zeroed. This follows from #6015
which made it into v2.5.1 and added the `omit_single_disc` option.

I've added tests and have used this locally for some time.

beetsplug/zero.py

@@ -123,12 +123,10 @@ class ZeroPlugin(BeetsPlugin):
         config.
         """
         fields_set = False
-
-        if "disc" in tags and self.config["omit_single_disc"].get(bool):
-            if item.disctotal == 1:
+        if self.config["omit_single_disc"].get(bool) and item.disctotal == 1:
+            for tag in {"disc", "disctotal"} & set(tags):
+                tags[tag] = None
                 fields_set = True
-                self._log.debug("disc: {.disc} -> None", item)
-                tags["disc"] = None
 
         if not self.fields_to_progs:
             self._log.warning("no fields list to remove")

docs/changelog.rst

@@ -41,6 +41,8 @@ Bug fixes
 
 - :doc:`plugins/ftintitle`: Fix handling of multiple featured artists with
   ampersand.
+- :doc:`plugins/zero`: When the ``omit_single_disc`` option is set,
+  ``disctotal`` is zeroed alongside ``disc``.
 
 For plugin developers
 ~~~~~~~~~~~~~~~~~~~~~

docs/plugins/zero.rst

@@ -31,9 +31,8 @@ to nullify and the conditions for nullifying them:
   ``keep_fields``---not both!
 - To conditionally filter a field, use ``field: [regexp, regexp]`` to specify
   regular expressions.
-- Set ``omit_single_disc`` to ``True`` to omit writing the ``disc`` number for
-  albums with only a single disc (``disctotal == 1``). By default, beets will
-  number the disc even if the album contains only one disc in total.
+- Set ``omit_single_disc`` to ``True`` to omit writing the ``disc`` number and
+  the ``disctotal`` number for albums with a single disc (``disctotal == 1``).
 - By default this plugin only affects files' tags; the beets database is left
   unchanged. To update the tags in the database, set the ``update_database``
   option to true.

test/plugins/test_zero.py

@@ -256,7 +256,8 @@ class ZeroPluginTest(IOMixin, PluginTestCase):
 
         mf = MediaFile(syspath(item.path))
         assert mf.comments is None
-        assert mf.disc == 0
+        assert mf.disc is None
+        assert mf.disctotal is None
 
     def test_omit_single_disc_with_tags_multi(self):
         item = self.add_item_fixture(
@@ -271,6 +272,7 @@ class ZeroPluginTest(IOMixin, PluginTestCase):
         mf = MediaFile(syspath(item.path))
         assert mf.comments is None
         assert mf.disc == 1
+        assert mf.disctotal == 4
 
     def test_omit_single_disc_only_change_single(self):
         item = self.add_item_fixture(disctotal=1, disc=1)
@@ -280,7 +282,8 @@ class ZeroPluginTest(IOMixin, PluginTestCase):
             item.write()
 
         mf = MediaFile(syspath(item.path))
-        assert mf.disc == 0
+        assert mf.disc is None
+        assert mf.disctotal is None
 
     def test_omit_single_disc_only_change_multi(self):
         item = self.add_item_fixture(disctotal=4, disc=1)
@@ -291,6 +294,7 @@ class ZeroPluginTest(IOMixin, PluginTestCase):
 
         mf = MediaFile(syspath(item.path))
         assert mf.disc == 1
+        assert mf.disctotal == 4
 
     def test_empty_query_n_response_no_changes(self):
         item = self.add_item_fixture(