Use topic_name() helper in more places.

zerver/lib/actions.py

@@ -4021,7 +4021,7 @@ def do_delete_message(user_profile: UserProfile, message: Message) -> None:
         'message_type': message_type, }  # type: Dict[str, Any]
     if message_type == "stream":
         event['stream_id'] = message.recipient.type_id
-        event['topic'] = message.subject
+        event['topic'] = message.topic_name()
     else:
         event['recipient_user_ids'] = message.recipient.type_id
 

zerver/lib/digest.py

@@ -96,7 +96,7 @@ def gather_hot_conversations(user_profile: UserProfile, stream_messages: QuerySe
             continue
 
         key = (user_message.message.recipient.type_id,
-               user_message.message.subject)
+               user_message.message.topic_name())
         conversation_diversity[key].add(
             user_message.message.sender.full_name)
         conversation_length[key] += 1

zerver/lib/email_mirror.py

@@ -104,7 +104,7 @@ def create_missed_message_address(user_profile: UserProfile, message: Message) -
     data = {
         'user_profile_id': user_profile.id,
         'recipient_id': recipient_id,
-        'subject': message.subject.encode('utf-8'),
+        'subject': message.topic_name().encode('utf-8'),
     }
 
     while True:

zerver/lib/notifications.py

@@ -192,9 +192,9 @@ def build_message_list(user_profile: UserProfile, messages: List[Message]) -> Li
             stream = Stream.objects.only('id', 'name').get(id=message.recipient.type_id)
             header = "%s > %s" % (stream.name, message.topic_name())
             stream_link = stream_narrow_url(user_profile.realm, stream)
-            topic_link = topic_narrow_url(user_profile.realm, stream, message.subject)
+            topic_link = topic_narrow_url(user_profile.realm, stream, message.topic_name())
             header_html = "<a href='%s'>%s</a> > <a href='%s'>%s</a>" % (
-                stream_link, stream.name, topic_link, message.subject)
+                stream_link, stream.name, topic_link, message.topic_name())
         return {"plain": header,
                 "html": header_html,
                 "stream_message": message.recipient.type_name() == "stream"}

zerver/views/messages.py

@@ -1277,7 +1277,7 @@ def fill_edit_history_entries(message_history: List[Dict[str, Any]], message: Me
     """
     prev_content = message.content
     prev_rendered_content = message.rendered_content
-    prev_topic = message.subject
+    prev_topic = message.topic_name()
 
     # Make sure that the latest entry in the history corresponds to the
     # message's last edit time