Extract filter_by_exact_message_topic().

zerver/lib/actions.py

@@ -55,6 +55,9 @@ from zerver.lib.stream_subscription import (
     num_subscribers_for_stream_id,
 )
 from zerver.lib.stream_topic import StreamTopicTarget
+from zerver.lib.topic import (
+    filter_by_exact_message_topic,
+)
 from zerver.lib.topic_mutes import (
     get_topic_mutes,
     add_topic_mute,
@@ -1784,15 +1787,19 @@ def already_sent_mirrored_message_id(message: Message) -> Optional[int]:
     else:
         time_window = datetime.timedelta(seconds=0)
 
-    messages = Message.objects.filter(
+    query = Message.objects.filter(
         sender=message.sender,
         recipient=message.recipient,
         content=message.content,
-        subject=message.subject,
         sending_client=message.sending_client,
         pub_date__gte=message.pub_date - time_window,
         pub_date__lte=message.pub_date + time_window)
 
+    messages = filter_by_exact_message_topic(
+        query=query,
+        message=message,
+    )
+
     if messages.exists():
         return messages[0].id
     return None

zerver/lib/topic.py

@@ -1,9 +1,18 @@
 from django.db import connection
+from django.db.models.query import QuerySet
 
-from zerver.models import UserProfile, Recipient
+from zerver.models import (
+    Message,
+    Recipient,
+    UserProfile,
+)
 
 from typing import Any, Dict, List, Tuple
 
+def filter_by_exact_message_topic(query: QuerySet, message: Message) -> QuerySet:
+    topic_name = message.topic_name()
+    return query.filter(subject=topic_name)
+
 def generate_topic_history_from_db_rows(rows: List[Tuple[str, int]]) -> List[Dict[str, Any]]:
     canonical_topic_names = {}  # type: Dict[str, Tuple[int, str]]