Fix formatting non-templated cell URLs with no config

If transport_url or connection are unset in config, we will fail to format
even non-templated cell mapping URLs due to an overly specific check in the
format routines. This fixes it by always bailing on templating if the config
is unset, and keeping the error message if we were unable to format a
template as a result.

Change-Id: I760580b8e6594be2bee99a5b825a690b07ab9deb
Closes-Bug: #1798158

nova/objects/cell_mapping.py

@@ -129,9 +129,10 @@ def _format_url(url, default):
 
     @staticmethod
     def _format_db_url(url):
-        if CONF.database.connection is None and '{' in url:
-            LOG.error('Cell mapping database_connection is a template, but '
-                      '[database]/connection is not set')
+        if CONF.database.connection is None:
+            if '{' in url:
+                LOG.error('Cell mapping database_connection is a template, '
+                          'but [database]/connection is not set')
             return url
         try:
             return CellMapping._format_url(url, CONF.database.connection)
@@ -142,9 +143,10 @@ def _format_db_url(url):
 
     @staticmethod
     def _format_mq_url(url):
-        if CONF.transport_url is None and '{' in url:
-            LOG.error('Cell mapping transport_url is a template, but '
-                      '[DEFAULT]/transport_url is not set')
+        if CONF.transport_url is None:
+            if '{' in url:
+                LOG.error('Cell mapping transport_url is a template, but '
+                          '[DEFAULT]/transport_url is not set')
             return url
         try:
             return CellMapping._format_url(url, CONF.transport_url)

nova/tests/unit/objects/test_cell_mapping.py

@@ -247,6 +247,23 @@ def test_formatted_url_without_base_set(self, mock_get):
         self.assertEqual(varurl, mapping_obj.database_connection)
         self.assertEqual(varurl, mapping_obj.transport_url)
 
+    @mock.patch.object(cell_mapping.CellMapping, '_get_by_uuid_from_db')
+    @mock.patch.object(cell_mapping.CellMapping, '_format_url')
+    def test_non_formatted_url_with_no_base(self, mock_format, mock_get):
+        # Make sure we just pass through the template URL if the base
+        # URLs are not set, i.e. we don't try to format the URL to a template.
+        url = 'foo'
+        self.flags(transport_url=None)
+        self.flags(connection=None, group='database')
+        db_mapping = get_db_mapping(transport_url=url,
+                                    database_connection=url)
+        mock_get.return_value = db_mapping
+        mapping_obj = objects.CellMapping().get_by_uuid(self.context,
+                db_mapping['uuid'])
+        self.assertEqual(url, mapping_obj.database_connection)
+        self.assertEqual(url, mapping_obj.transport_url)
+        mock_format.assert_not_called()
+
 
 class TestCellMappingObject(test_objects._LocalTest,
                             _TestCellMappingObject):