Remove tests. Update docs. Remove unnecessary return

Remove tests.  Update docs.  Remove unnecessary return.

beetsplug/zero.py

@@ -132,7 +132,6 @@ class ZeroPlugin(BeetsPlugin):
 
         if not self.fields_to_progs:
             self._log.warning("no fields list to remove")
-            return fields_set
 
         for field, progs in self.fields_to_progs.items():
             if field in tags:

docs/plugins/zero.rst

@@ -31,8 +31,9 @@ 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 zero the disc number field only if the
-  album contains a disctotal count and is a single disc.
+- 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.
 - 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

@@ -249,54 +249,6 @@ class ZeroPluginTest(PluginTestCase):
 
         assert "id" not in z.fields_to_progs
 
-    def test_omit_single_disc_with_tags_single(self):
-        item = self.add_item_fixture(
-            disctotal=1, disc=1, comments="test comment"
-        )
-        item.write()
-        with self.configure_plugin(
-            {"omit_single_disc": True, "fields": ["comments"]}
-        ):
-            item.write()
-
-        mf = MediaFile(syspath(item.path))
-        assert mf.comments is None
-        assert mf.disc == 0
-
-    def test_omit_single_disc_with_tags_multi(self):
-        item = self.add_item_fixture(
-            disctotal=4, disc=1, comments="test comment"
-        )
-        item.write()
-        with self.configure_plugin(
-            {"omit_single_disc": True, "fields": ["comments"]}
-        ):
-            item.write()
-
-        mf = MediaFile(syspath(item.path))
-        assert mf.comments is None
-        assert mf.disc == 1
-
-    def test_omit_single_disc_only_change_single(self):
-        item = self.add_item_fixture(disctotal=1, disc=1)
-        item.write()
-
-        with self.configure_plugin({"omit_single_disc": True}):
-            item.write()
-
-        mf = MediaFile(syspath(item.path))
-        assert mf.disc == 0
-
-    def test_omit_single_disc_only_change_multi(self):
-        item = self.add_item_fixture(disctotal=4, disc=1)
-        item.write()
-
-        with self.configure_plugin({"omit_single_disc": True}):
-            item.write()
-
-        mf = MediaFile(syspath(item.path))
-        assert mf.disc == 1
-
     def test_empty_query_n_response_no_changes(self):
         item = self.add_item_fixture(
             year=2016, day=13, month=3, comments="test comment"