Use shared inboxes for mentions too

bookwyrm/models/activitypub_mixin.py

@@ -152,8 +152,9 @@ def get_recipients(self, software=None) -> list[str]:
         # find anyone who's tagged in a status, for example
         mentions = self.recipients if hasattr(self, "recipients") else []
 
-        # we always send activities to explicitly mentioned users' inboxes
-        recipients = [u.inbox for u in mentions or [] if not u.local]
+        # we always send activities to explicitly mentioned users (using shared inboxes
+        # where available to avoid duplicate submissions to a given instance)
+        recipients = {u.shared_inbox or u.inbox for u in mentions if not u.local}
 
         # unless it's a dm, all the followers should receive the activity
         if privacy != "direct":
@@ -173,18 +174,18 @@ def get_recipients(self, software=None) -> list[str]:
             if user:
                 queryset = queryset.filter(following=user)
 
-            # ideally, we will send to shared inboxes for efficiency
-            shared_inboxes = (
-                queryset.filter(shared_inbox__isnull=False)
-                .values_list("shared_inbox", flat=True)
-                .distinct()
+            # as above, we prefer shared inboxes if available
+            recipients.update(
+                queryset.filter(shared_inbox__isnull=False).values_list(
+                    "shared_inbox", flat=True
+                )
             )
-            # but not everyone has a shared inbox
-            inboxes = queryset.filter(shared_inbox__isnull=True).values_list(
-                "inbox", flat=True
+            recipients.update(
+                queryset.filter(shared_inbox__isnull=True).values_list(
+                    "inbox", flat=True
+                )
             )
-            recipients += list(shared_inboxes) + list(inboxes)
-        return list(set(recipients))
+        return list(recipients)
 
     def to_activity_dataclass(self):
         """convert from a model to an activity"""

bookwyrm/models/status.py

@@ -107,14 +107,14 @@ def delete(self, *args, **kwargs):  # pylint: disable=unused-argument
     @property
     def recipients(self):
         """tagged users who definitely need to get this status in broadcast"""
-        mentions = [u for u in self.mention_users.all() if not u.local]
+        mentions = {u for u in self.mention_users.all() if not u.local}
         if (
             hasattr(self, "reply_parent")
             and self.reply_parent
             and not self.reply_parent.user.local
         ):
-            mentions.append(self.reply_parent.user)
-        return list(set(mentions))
+            mentions.add(self.reply_parent.user)
+        return list(mentions)
 
     @classmethod
     def ignore_activity(

bookwyrm/tests/models/test_activitypub_mixin.py

@@ -227,14 +227,18 @@ def test_get_recipients_combine_inboxes(self, *_):
                 shared_inbox="http://example.com/inbox",
                 outbox="https://example.com/users/nutria/outbox",
             )
-        MockSelf = namedtuple("Self", ("privacy", "user"))
-        mock_self = MockSelf("public", self.local_user)
+        MockSelf = namedtuple("Self", ("privacy", "user", "recipients"))
         self.local_user.followers.add(self.remote_user)
         self.local_user.followers.add(another_remote_user)
 
+        mock_self = MockSelf("public", self.local_user, [])
         recipients = ActivitypubMixin.get_recipients(mock_self)
-        self.assertEqual(len(recipients), 1)
-        self.assertEqual(recipients[0], "http://example.com/inbox")
+        self.assertCountEqual(recipients, ["http://example.com/inbox"])
+
+        # should also work with recipient that is a follower
+        mock_self.recipients.append(another_remote_user)
+        recipients = ActivitypubMixin.get_recipients(mock_self)
+        self.assertCountEqual(recipients, ["http://example.com/inbox"])
 
     def test_get_recipients_software(self, *_):
         """should differentiate between bookwyrm and other remote users"""