Properly format 'attached to' column list when listing volumes

Previously, no data was being returned for the 'attached to' field
when listing volumes. Dig into the the returned array to format
the column.

Change-Id: Iebd79e5ddcb4a335703d9b2675aa7128995de918
Closes-Bug: #1404931

openstackclient/volume/v1/volume.py

@@ -221,6 +221,25 @@ class ListVolume(lister.Lister):
     def take_action(self, parsed_args):
         self.log.debug('take_action(%s)', parsed_args)
 
+        volume_client = self.app.client_manager.volume
+        compute_client = self.app.client_manager.compute
+
+        def _format_attach(attachments):
+            """Return a formatted string of a volume's attached instances
+
+            :param volume: a volume.attachments field
+            :rtype: a string of formatted instances
+            """
+
+            msg = ''
+            for attachment in attachments:
+                server = attachment['server_id']
+                if server in server_cache.keys():
+                    server = server_cache[server].name
+                device = attachment['device']
+                msg += 'Attached to %s on %s ' % (server, device)
+            return msg
+
         if parsed_args.long:
             columns = (
                 'ID',
@@ -229,7 +248,7 @@ class ListVolume(lister.Lister):
                 'Size',
                 'Volume Type',
                 'Bootable',
-                'Attached to',
+                'Attachments',
                 'Metadata',
             )
             column_headers = (
@@ -239,7 +258,7 @@ class ListVolume(lister.Lister):
                 'Size',
                 'Type',
                 'Bootable',
-                'Attached',
+                'Attached to',
                 'Properties',
             )
         else:
@@ -248,28 +267,38 @@ class ListVolume(lister.Lister):
                 'Display Name',
                 'Status',
                 'Size',
-                'Attached to',
+                'Attachments',
             )
             column_headers = (
                 'ID',
                 'Display Name',
                 'Status',
                 'Size',
-                'Attached',
+                'Attached to',
             )
+
+        # Cache the server list
+        server_cache = {}
+        try:
+            for s in compute_client.servers.list():
+                server_cache[s.id] = s
+        except Exception:
+            # Just forget it if there's any trouble
+            pass
+
         search_opts = {
             'all_tenants': parsed_args.all_projects,
             'display_name': parsed_args.name,
             'status': parsed_args.status,
         }
 
-        volume_client = self.app.client_manager.volume
         data = volume_client.volumes.list(search_opts=search_opts)
 
         return (column_headers,
                 (utils.get_item_properties(
                     s, columns,
-                    formatters={'Metadata': utils.format_dict},
+                    formatters={'Metadata': utils.format_dict,
+                                'Attachments': _format_attach},
                 ) for s in data))