Allow limiting threads by participation.

synapse/handlers/relations.py

@@ -485,6 +485,7 @@ class RelationsHandler:
         self,
         requester: Requester,
         room_id: str,
+        include: str,
         limit: int = 5,
         from_token: Optional[StreamToken] = None,
         to_token: Optional[StreamToken] = None,
@@ -494,6 +495,8 @@ class RelationsHandler:
         Args:
             requester: The user requesting the relations.
             room_id: The room the event belongs to.
+            include: One of "all" or "participated" to indicate which threads should
+                be returned.
             limit: Only fetch the most recent `limit` events.
             from_token: Fetch rows from the given token, or from the start if None.
             to_token: Fetch rows up to the given token, or up to the end if None.
@@ -518,6 +521,21 @@ class RelationsHandler:
 
         events = await self._main_store.get_events_as_list(thread_roots)
 
+        if include == "participated":
+            # Pre-seed thread participation with whether the requester sent the event.
+            participated = {event.event_id: event.sender == user_id for event in events}
+            # For events the requester did not send, check the database for whether
+            # the requester sent a threaded reply.
+            participated.update(
+                await self._main_store.get_threads_participated(
+                    [eid for eid, p in participated.items() if not p],
+                    user_id,
+                )
+            )
+
+            # Limit the returned threads to those the user has participated in.
+            events = [event for event in events if participated[event.event_id]]
+
         events = await filter_events_for_client(
             self._storage_controllers,
             user_id,

synapse/rest/client/relations.py

@@ -113,6 +113,9 @@ class ThreadsServlet(RestServlet):
         limit = parse_integer(request, "limit", default=5)
         from_token_str = parse_string(request, "from")
         to_token_str = parse_string(request, "to")
+        include = parse_string(
+            request, "include", default="all", allowed_values=["all", "participated"]
+        )
 
         # Return the relations
         from_token = None
@@ -125,6 +128,7 @@ class ThreadsServlet(RestServlet):
         result = await self._relations_handler.get_threads(
             requester=requester,
             room_id=room_id,
+            include=include,
             limit=limit,
             from_token=from_token,
             to_token=to_token,

tests/rest/client/test_relations.py

@@ -1750,4 +1750,50 @@ class ThreadsTestCase(BaseRelationsTestCase):
 
         self.assertNotIn("next_batch", channel.json_body, channel.json_body)
 
+    @unittest.override_config({"experimental_features": {"msc3856_enabled": True}})
+    def test_include(self) -> None:
+        """Filtering threads to all or participated in should work."""
+        # Thread 1 has the user as the root event.
+        thread_1 = self.parent_id
+        self._send_relation(
+            RelationTypes.THREAD, "m.room.test", access_token=self.user2_token
+        )
+
+        # Thread 2 has the user replying.
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user2_token)
+        thread_2 = res["event_id"]
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Thread 3 has the user not participating in.
+        res = self.helper.send(self.room, body="Another thread!", tok=self.user2_token)
+        thread_3 = res["event_id"]
+        self._send_relation(
+            RelationTypes.THREAD,
+            "m.room.test",
+            access_token=self.user2_token,
+            parent_id=thread_3,
+        )
+
+        # All threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/unstable/org.matrix.msc3856/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(
+            thread_roots, [thread_3, thread_2, thread_1], channel.json_body
+        )
+
+        # Only participated threads.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/unstable/org.matrix.msc3856/rooms/{self.room}/threads?include=participated",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_2, thread_1], channel.json_body)
+
     # XXX Test ignoring users.