snapshot of https://github.com/zulip/zulip.git @ 48c69911c7dd4e03b20552eb3bd77ad8151c1357 (2026-09-15)

zerver/actions/submessage.py

@@ -0,0 +1,98 @@
+from django.utils.translation import gettext as _
+
+from zerver.actions.user_topics import do_set_user_topic_visibility_policy
+from zerver.lib.exceptions import JsonableError
+from zerver.lib.message import (
+    event_recipient_ids_for_action_on_messages,
+    set_visibility_policy_possible,
+    should_change_visibility_policy,
+    visibility_policy_for_participation,
+)
+from zerver.lib.streams import access_stream_by_id
+from zerver.models import Realm, SubMessage, UserProfile
+from zerver.tornado.django_api import send_event_on_commit
+
+
+def verify_submessage_sender(
+    *,
+    message_id: int,
+    message_sender_id: int,
+    submessage_sender_id: int,
+) -> None:
+    """Even though our submessage architecture is geared toward
+    collaboration among all message readers, we still enforce
+    the first person to attach a submessage to the message
+    must be the original sender of the message.
+    """
+
+    if message_sender_id == submessage_sender_id:
+        return
+
+    if SubMessage.objects.filter(
+        message_id=message_id,
+        sender_id=message_sender_id,
+    ).exists():
+        return
+
+    raise JsonableError(_("You cannot attach a submessage to this message."))
+
+
+def do_add_submessage(
+    realm: Realm,
+    sender_id: int,
+    message_id: int,
+    msg_type: str,
+    content: str,
+) -> None:
+    """Should be called while holding a SELECT FOR UPDATE lock
+    (e.g. via access_message(..., lock_message=True)) on the
+    Message row, to prevent race conditions.
+    """
+    submessage = SubMessage(
+        sender_id=sender_id,
+        message_id=message_id,
+        msg_type=msg_type,
+        content=content,
+    )
+    submessage.save()
+
+    # Determine and set the visibility_policy depending on 'automatically_follow_topics_policy'
+    # and 'automatically_unmute_topics_policy'.
+    sender = submessage.sender
+    if set_visibility_policy_possible(
+        sender, submessage.message
+    ) and UserProfile.AUTOMATICALLY_CHANGE_VISIBILITY_POLICY_ON_PARTICIPATION in [
+        sender.automatically_follow_topics_policy,
+        sender.automatically_unmute_topics_in_muted_streams_policy,
+    ]:
+        stream_id = submessage.message.recipient.type_id
+        (stream, sub) = access_stream_by_id(sender, stream_id)
+        assert stream is not None
+        if sub:
+            new_visibility_policy = visibility_policy_for_participation(sender, sub.is_muted)
+            if new_visibility_policy and should_change_visibility_policy(
+                new_visibility_policy,
+                sender,
+                stream_id,
+                topic_name=submessage.message.topic_name(),
+            ):
+                do_set_user_topic_visibility_policy(
+                    user_profile=sender,
+                    stream=stream,
+                    topic_name=submessage.message.topic_name(),
+                    visibility_policy=new_visibility_policy,
+                )
+
+    event = dict(
+        type="submessage",
+        msg_type=msg_type,
+        message_id=message_id,
+        submessage_id=submessage.id,
+        sender_id=sender_id,
+        content=content,
+    )
+    target_user_ids = event_recipient_ids_for_action_on_messages(
+        [submessage.message.id], submessage.message.is_channel_message
+    )
+
+    send_event_on_commit(realm, event, target_user_ids)