Return some room data in Sliding Sync `/sync` (#17320)

 - Timeline events
 - Stripped `invite_state`

Based on [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): Sliding Sync

2 files changed, 1073 insertions, 10 deletions

diff --git a/tests/rest/client/test_sync.py b/tests/rest/client/test_sync.py
index 12c11f342c..966c622e14 100644
--- a/tests/rest/client/test_sync.py
+++ b/tests/rest/client/test_sync.py
@@ -31,12 +31,13 @@ from synapse.api.constants import (
     AccountDataTypes,
     EventContentFields,
     EventTypes,
+    HistoryVisibility,
     ReceiptTypes,
     RelationTypes,
 )
 from synapse.rest.client import devices, knock, login, read_marker, receipts, room, sync
 from synapse.server import HomeServer
-from synapse.types import JsonDict, RoomStreamToken, StreamKeyType
+from synapse.types import JsonDict, RoomStreamToken, StreamKeyType, StreamToken, UserID
 from synapse.util import Clock
 
 from tests import unittest
@@ -1326,7 +1327,7 @@ class SlidingSyncTestCase(unittest.HomeserverTestCase):
 
     def test_sync_list(self) -> None:
         """
-        Test that room IDs show up in the Sliding Sync lists
+        Test that room IDs show up in the Sliding Sync `lists`
         """
         alice_user_id = self.register_user("alice", "correcthorse")
         alice_access_token = self.login(alice_user_id, "correcthorse")
@@ -1425,15 +1426,13 @@ class SlidingSyncTestCase(unittest.HomeserverTestCase):
         channel.await_result(timeout_ms=200)
         self.assertEqual(channel.code, 200, channel.json_body)
 
-        # We expect the `next_pos` in the result to be the same as what we requested
+        # We expect the next `pos` in the result to be the same as what we requested
         # with because we weren't able to find anything new yet.
-        self.assertEqual(
-            channel.json_body["next_pos"], future_position_token_serialized
-        )
+        self.assertEqual(channel.json_body["pos"], future_position_token_serialized)
 
     def test_filter_list(self) -> None:
         """
-        Test that filters apply to lists
+        Test that filters apply to `lists`
         """
         user1_id = self.register_user("user1", "pass")
         user1_tok = self.login(user1_id, "pass")
@@ -1564,7 +1563,7 @@ class SlidingSyncTestCase(unittest.HomeserverTestCase):
 
     def test_sort_list(self) -> None:
         """
-        Test that the lists are sorted by `stream_ordering`
+        Test that the `lists` are sorted by `stream_ordering`
         """
         user1_id = self.register_user("user1", "pass")
         user1_tok = self.login(user1_id, "pass")
@@ -1618,3 +1617,1067 @@ class SlidingSyncTestCase(unittest.HomeserverTestCase):
             ],
             channel.json_body["lists"]["foo-list"],
         )
+
+    def test_sliced_windows(self) -> None:
+        """
+        Test that the `lists` `ranges` are sliced correctly. Both sides of each range
+        are inclusive.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+
+        _room_id1 = self.helper.create_room_as(user1_id, tok=user1_tok, is_public=True)
+        room_id2 = self.helper.create_room_as(user1_id, tok=user1_tok, is_public=True)
+        room_id3 = self.helper.create_room_as(user1_id, tok=user1_tok, is_public=True)
+
+        # Make the Sliding Sync request for a single room
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 0]],
+                        "required_state": [
+                            ["m.room.join_rules", ""],
+                            ["m.room.history_visibility", ""],
+                            ["m.space.child", "*"],
+                        ],
+                        "timeline_limit": 1,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # Make sure it has the foo-list we requested
+        self.assertListEqual(
+            list(channel.json_body["lists"].keys()),
+            ["foo-list"],
+            channel.json_body["lists"].keys(),
+        )
+        # Make sure the list is sorted in the way we expect
+        self.assertListEqual(
+            list(channel.json_body["lists"]["foo-list"]["ops"]),
+            [
+                {
+                    "op": "SYNC",
+                    "range": [0, 0],
+                    "room_ids": [room_id3],
+                }
+            ],
+            channel.json_body["lists"]["foo-list"],
+        )
+
+        # Make the Sliding Sync request for the first two rooms
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [
+                            ["m.room.join_rules", ""],
+                            ["m.room.history_visibility", ""],
+                            ["m.space.child", "*"],
+                        ],
+                        "timeline_limit": 1,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # Make sure it has the foo-list we requested
+        self.assertListEqual(
+            list(channel.json_body["lists"].keys()),
+            ["foo-list"],
+            channel.json_body["lists"].keys(),
+        )
+        # Make sure the list is sorted in the way we expect
+        self.assertListEqual(
+            list(channel.json_body["lists"]["foo-list"]["ops"]),
+            [
+                {
+                    "op": "SYNC",
+                    "range": [0, 1],
+                    "room_ids": [room_id3, room_id2],
+                }
+            ],
+            channel.json_body["lists"]["foo-list"],
+        )
+
+    def test_rooms_limited_initial_sync(self) -> None:
+        """
+        Test that we mark `rooms` as `limited=True` when we saturate the `timeline_limit`
+        on initial sync.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity1", tok=user2_tok)
+        self.helper.send(room_id1, "activity2", tok=user2_tok)
+        event_response3 = self.helper.send(room_id1, "activity3", tok=user2_tok)
+        event_pos3 = self.get_success(
+            self.store.get_position_for_event(event_response3["event_id"])
+        )
+        event_response4 = self.helper.send(room_id1, "activity4", tok=user2_tok)
+        event_pos4 = self.get_success(
+            self.store.get_position_for_event(event_response4["event_id"])
+        )
+        event_response5 = self.helper.send(room_id1, "activity5", tok=user2_tok)
+        user1_join_response = self.helper.join(room_id1, user1_id, tok=user1_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": 3,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # We expect to saturate the `timeline_limit` (there are more than 3 messages in the room)
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            True,
+            channel.json_body["rooms"][room_id1],
+        )
+        # Check to make sure the latest events are returned
+        self.assertEqual(
+            [
+                event["event_id"]
+                for event in channel.json_body["rooms"][room_id1]["timeline"]
+            ],
+            [
+                event_response4["event_id"],
+                event_response5["event_id"],
+                user1_join_response["event_id"],
+            ],
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+
+        # Check to make sure the `prev_batch` points at the right place
+        prev_batch_token = self.get_success(
+            StreamToken.from_string(
+                self.store, channel.json_body["rooms"][room_id1]["prev_batch"]
+            )
+        )
+        prev_batch_room_stream_token_serialized = self.get_success(
+            prev_batch_token.room_key.to_string(self.store)
+        )
+        # If we use the `prev_batch` token to look backwards, we should see `event3`
+        # next so make sure the token encompasses it
+        self.assertEqual(
+            event_pos3.persisted_after(prev_batch_token.room_key),
+            False,
+            f"`prev_batch` token {prev_batch_room_stream_token_serialized} should be >= event_pos3={self.get_success(event_pos3.to_room_stream_token().to_string(self.store))}",
+        )
+        # If we use the `prev_batch` token to look backwards, we shouldn't see `event4`
+        # anymore since it was just returned in this response.
+        self.assertEqual(
+            event_pos4.persisted_after(prev_batch_token.room_key),
+            True,
+            f"`prev_batch` token {prev_batch_room_stream_token_serialized} should be < event_pos4={self.get_success(event_pos4.to_room_stream_token().to_string(self.store))}",
+        )
+
+        # With no `from_token` (initial sync), it's all historical since there is no
+        # "live" range
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            0,
+            channel.json_body["rooms"][room_id1],
+        )
+
+    def test_rooms_not_limited_initial_sync(self) -> None:
+        """
+        Test that we mark `rooms` as `limited=False` when there are no more events to
+        paginate to.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity1", tok=user2_tok)
+        self.helper.send(room_id1, "activity2", tok=user2_tok)
+        self.helper.send(room_id1, "activity3", tok=user2_tok)
+        self.helper.join(room_id1, user1_id, tok=user1_tok)
+
+        # Make the Sliding Sync request
+        timeline_limit = 100
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": timeline_limit,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # The timeline should be `limited=False` because we have all of the events (no
+        # more to paginate to)
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            False,
+            channel.json_body["rooms"][room_id1],
+        )
+        expected_number_of_events = 9
+        # We're just looking to make sure we got all of the events before hitting the `timeline_limit`
+        self.assertEqual(
+            len(channel.json_body["rooms"][room_id1]["timeline"]),
+            expected_number_of_events,
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+        self.assertLessEqual(expected_number_of_events, timeline_limit)
+
+        # With no `from_token` (initial sync), it's all historical since there is no
+        # "live" token range.
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            0,
+            channel.json_body["rooms"][room_id1],
+        )
+
+    def test_rooms_incremental_sync(self) -> None:
+        """
+        Test `rooms` data during an incremental sync after an initial sync.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.join(room_id1, user1_id, tok=user1_tok)
+        self.helper.send(room_id1, "activity before initial sync1", tok=user2_tok)
+
+        # Make an initial Sliding Sync request to grab a token. This is also a sanity
+        # check that we can go from initial to incremental sync.
+        sync_params = {
+            "lists": {
+                "foo-list": {
+                    "ranges": [[0, 1]],
+                    "required_state": [],
+                    "timeline_limit": 3,
+                }
+            }
+        }
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            sync_params,
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+        next_pos = channel.json_body["pos"]
+
+        # Send some events but don't send enough to saturate the `timeline_limit`.
+        # We want to later test that we only get the new events since the `next_pos`
+        event_response2 = self.helper.send(room_id1, "activity after2", tok=user2_tok)
+        event_response3 = self.helper.send(room_id1, "activity after3", tok=user2_tok)
+
+        # Make an incremental Sliding Sync request (what we're trying to test)
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint + f"?pos={next_pos}",
+            sync_params,
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # We only expect to see the new events since the last sync which isn't enough to
+        # fill up the `timeline_limit`.
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            False,
+            f'Our `timeline_limit` was {sync_params["lists"]["foo-list"]["timeline_limit"]} '
+            + f'and {len(channel.json_body["rooms"][room_id1]["timeline"])} events were returned in the timeline. '
+            + str(channel.json_body["rooms"][room_id1]),
+        )
+        # Check to make sure the latest events are returned
+        self.assertEqual(
+            [
+                event["event_id"]
+                for event in channel.json_body["rooms"][room_id1]["timeline"]
+            ],
+            [
+                event_response2["event_id"],
+                event_response3["event_id"],
+            ],
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+
+        # All events are "live"
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            2,
+            channel.json_body["rooms"][room_id1],
+        )
+
+    def test_rooms_newly_joined_incremental_sync(self) -> None:
+        """
+        Test that when we make an incremental sync with a `newly_joined` `rooms`, we are
+        able to see some historical events before the `from_token`.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity before token1", tok=user2_tok)
+        event_response2 = self.helper.send(
+            room_id1, "activity before token2", tok=user2_tok
+        )
+
+        from_token = self.event_sources.get_current_token()
+
+        # Join the room after the `from_token` which will make us consider this room as
+        # `newly_joined`.
+        user1_join_response = self.helper.join(room_id1, user1_id, tok=user1_tok)
+
+        # Send some events but don't send enough to saturate the `timeline_limit`.
+        # We want to later test that we only get the new events since the `next_pos`
+        event_response3 = self.helper.send(
+            room_id1, "activity after token3", tok=user2_tok
+        )
+        event_response4 = self.helper.send(
+            room_id1, "activity after token4", tok=user2_tok
+        )
+
+        # The `timeline_limit` is set to 4 so we can at least see one historical event
+        # before the `from_token`. We should see historical events because this is a
+        # `newly_joined` room.
+        timeline_limit = 4
+        # Make an incremental Sliding Sync request (what we're trying to test)
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint
+            + f"?pos={self.get_success(from_token.to_string(self.store))}",
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": timeline_limit,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # We should see the new events and the rest should be filled with historical
+        # events which will make us `limited=True` since there are more to paginate to.
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            True,
+            f"Our `timeline_limit` was {timeline_limit} "
+            + f'and {len(channel.json_body["rooms"][room_id1]["timeline"])} events were returned in the timeline. '
+            + str(channel.json_body["rooms"][room_id1]),
+        )
+        # Check to make sure that the "live" and historical events are returned
+        self.assertEqual(
+            [
+                event["event_id"]
+                for event in channel.json_body["rooms"][room_id1]["timeline"]
+            ],
+            [
+                event_response2["event_id"],
+                user1_join_response["event_id"],
+                event_response3["event_id"],
+                event_response4["event_id"],
+            ],
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+
+        # Only events after the `from_token` are "live" (join, event3, event4)
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            3,
+            channel.json_body["rooms"][room_id1],
+        )
+
+    def test_rooms_invite_shared_history_initial_sync(self) -> None:
+        """
+        Test that `rooms` we are invited to have some stripped `invite_state` during an
+        initial sync.
+
+        This is an `invite` room so we should only have `stripped_state` (no `timeline`)
+        but we also shouldn't see any timeline events because the history visiblity is
+        `shared` and we haven't joined the room yet.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user1 = UserID.from_string(user1_id)
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user2 = UserID.from_string(user2_id)
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        # Ensure we're testing with a room with `shared` history visibility which means
+        # history visible until you actually join the room.
+        history_visibility_response = self.helper.get_state(
+            room_id1, EventTypes.RoomHistoryVisibility, tok=user2_tok
+        )
+        self.assertEqual(
+            history_visibility_response.get("history_visibility"),
+            HistoryVisibility.SHARED,
+        )
+
+        self.helper.send(room_id1, "activity before1", tok=user2_tok)
+        self.helper.send(room_id1, "activity before2", tok=user2_tok)
+        self.helper.invite(room_id1, src=user2_id, targ=user1_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity after3", tok=user2_tok)
+        self.helper.send(room_id1, "activity after4", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": 3,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # `timeline` is omitted for `invite` rooms with `stripped_state`
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("timeline"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `num_live` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("num_live"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `limited` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("limited"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `prev_batch` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("prev_batch"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # We should have some `stripped_state` so the potential joiner can identify the
+        # room (we don't care about the order).
+        self.assertCountEqual(
+            channel.json_body["rooms"][room_id1]["invite_state"],
+            [
+                {
+                    "content": {"creator": user2_id, "room_version": "10"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.create",
+                },
+                {
+                    "content": {"join_rule": "public"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.join_rules",
+                },
+                {
+                    "content": {"displayname": user2.localpart, "membership": "join"},
+                    "sender": user2_id,
+                    "state_key": user2_id,
+                    "type": "m.room.member",
+                },
+                {
+                    "content": {"displayname": user1.localpart, "membership": "invite"},
+                    "sender": user2_id,
+                    "state_key": user1_id,
+                    "type": "m.room.member",
+                },
+            ],
+            channel.json_body["rooms"][room_id1]["invite_state"],
+        )
+
+    def test_rooms_invite_shared_history_incremental_sync(self) -> None:
+        """
+        Test that `rooms` we are invited to have some stripped `invite_state` during an
+        incremental sync.
+
+        This is an `invite` room so we should only have `stripped_state` (no `timeline`)
+        but we also shouldn't see any timeline events because the history visiblity is
+        `shared` and we haven't joined the room yet.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user1 = UserID.from_string(user1_id)
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user2 = UserID.from_string(user2_id)
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        # Ensure we're testing with a room with `shared` history visibility which means
+        # history visible until you actually join the room.
+        history_visibility_response = self.helper.get_state(
+            room_id1, EventTypes.RoomHistoryVisibility, tok=user2_tok
+        )
+        self.assertEqual(
+            history_visibility_response.get("history_visibility"),
+            HistoryVisibility.SHARED,
+        )
+
+        self.helper.send(room_id1, "activity before invite1", tok=user2_tok)
+        self.helper.send(room_id1, "activity before invite2", tok=user2_tok)
+        self.helper.invite(room_id1, src=user2_id, targ=user1_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity after invite3", tok=user2_tok)
+        self.helper.send(room_id1, "activity after invite4", tok=user2_tok)
+
+        from_token = self.event_sources.get_current_token()
+
+        self.helper.send(room_id1, "activity after token5", tok=user2_tok)
+        self.helper.send(room_id1, "activity after toekn6", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint
+            + f"?pos={self.get_success(from_token.to_string(self.store))}",
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": 3,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # `timeline` is omitted for `invite` rooms with `stripped_state`
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("timeline"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `num_live` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("num_live"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `limited` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("limited"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `prev_batch` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("prev_batch"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # We should have some `stripped_state` so the potential joiner can identify the
+        # room (we don't care about the order).
+        self.assertCountEqual(
+            channel.json_body["rooms"][room_id1]["invite_state"],
+            [
+                {
+                    "content": {"creator": user2_id, "room_version": "10"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.create",
+                },
+                {
+                    "content": {"join_rule": "public"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.join_rules",
+                },
+                {
+                    "content": {"displayname": user2.localpart, "membership": "join"},
+                    "sender": user2_id,
+                    "state_key": user2_id,
+                    "type": "m.room.member",
+                },
+                {
+                    "content": {"displayname": user1.localpart, "membership": "invite"},
+                    "sender": user2_id,
+                    "state_key": user1_id,
+                    "type": "m.room.member",
+                },
+            ],
+            channel.json_body["rooms"][room_id1]["invite_state"],
+        )
+
+    def test_rooms_invite_world_readable_history_initial_sync(self) -> None:
+        """
+        Test that `rooms` we are invited to have some stripped `invite_state` during an
+        initial sync.
+
+        This is an `invite` room so we should only have `stripped_state` (no `timeline`)
+        but depending on the semantics we decide, we could potentially see some
+        historical events before/after the `from_token` because the history is
+        `world_readable`. Same situation for events after the `from_token` if the
+        history visibility was set to `invited`.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user1 = UserID.from_string(user1_id)
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user2 = UserID.from_string(user2_id)
+
+        room_id1 = self.helper.create_room_as(
+            user2_id,
+            tok=user2_tok,
+            extra_content={
+                "preset": "public_chat",
+                "initial_state": [
+                    {
+                        "content": {
+                            "history_visibility": HistoryVisibility.WORLD_READABLE
+                        },
+                        "state_key": "",
+                        "type": EventTypes.RoomHistoryVisibility,
+                    }
+                ],
+            },
+        )
+        # Ensure we're testing with a room with `world_readable` history visibility
+        # which means events are visible to anyone even without membership.
+        history_visibility_response = self.helper.get_state(
+            room_id1, EventTypes.RoomHistoryVisibility, tok=user2_tok
+        )
+        self.assertEqual(
+            history_visibility_response.get("history_visibility"),
+            HistoryVisibility.WORLD_READABLE,
+        )
+
+        self.helper.send(room_id1, "activity before1", tok=user2_tok)
+        self.helper.send(room_id1, "activity before2", tok=user2_tok)
+        self.helper.invite(room_id1, src=user2_id, targ=user1_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity after3", tok=user2_tok)
+        self.helper.send(room_id1, "activity after4", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        # Large enough to see the latest events and before the invite
+                        "timeline_limit": 4,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # `timeline` is omitted for `invite` rooms with `stripped_state`
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("timeline"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `num_live` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("num_live"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `limited` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("limited"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `prev_batch` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("prev_batch"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # We should have some `stripped_state` so the potential joiner can identify the
+        # room (we don't care about the order).
+        self.assertCountEqual(
+            channel.json_body["rooms"][room_id1]["invite_state"],
+            [
+                {
+                    "content": {"creator": user2_id, "room_version": "10"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.create",
+                },
+                {
+                    "content": {"join_rule": "public"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.join_rules",
+                },
+                {
+                    "content": {"displayname": user2.localpart, "membership": "join"},
+                    "sender": user2_id,
+                    "state_key": user2_id,
+                    "type": "m.room.member",
+                },
+                {
+                    "content": {"displayname": user1.localpart, "membership": "invite"},
+                    "sender": user2_id,
+                    "state_key": user1_id,
+                    "type": "m.room.member",
+                },
+            ],
+            channel.json_body["rooms"][room_id1]["invite_state"],
+        )
+
+    def test_rooms_invite_world_readable_history_incremental_sync(self) -> None:
+        """
+        Test that `rooms` we are invited to have some stripped `invite_state` during an
+        incremental sync.
+
+        This is an `invite` room so we should only have `stripped_state` (no `timeline`)
+        but depending on the semantics we decide, we could potentially see some
+        historical events before/after the `from_token` because the history is
+        `world_readable`. Same situation for events after the `from_token` if the
+        history visibility was set to `invited`.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user1 = UserID.from_string(user1_id)
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user2 = UserID.from_string(user2_id)
+
+        room_id1 = self.helper.create_room_as(
+            user2_id,
+            tok=user2_tok,
+            extra_content={
+                "preset": "public_chat",
+                "initial_state": [
+                    {
+                        "content": {
+                            "history_visibility": HistoryVisibility.WORLD_READABLE
+                        },
+                        "state_key": "",
+                        "type": EventTypes.RoomHistoryVisibility,
+                    }
+                ],
+            },
+        )
+        # Ensure we're testing with a room with `world_readable` history visibility
+        # which means events are visible to anyone even without membership.
+        history_visibility_response = self.helper.get_state(
+            room_id1, EventTypes.RoomHistoryVisibility, tok=user2_tok
+        )
+        self.assertEqual(
+            history_visibility_response.get("history_visibility"),
+            HistoryVisibility.WORLD_READABLE,
+        )
+
+        self.helper.send(room_id1, "activity before invite1", tok=user2_tok)
+        self.helper.send(room_id1, "activity before invite2", tok=user2_tok)
+        self.helper.invite(room_id1, src=user2_id, targ=user1_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity after invite3", tok=user2_tok)
+        self.helper.send(room_id1, "activity after invite4", tok=user2_tok)
+
+        from_token = self.event_sources.get_current_token()
+
+        self.helper.send(room_id1, "activity after token5", tok=user2_tok)
+        self.helper.send(room_id1, "activity after toekn6", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint
+            + f"?pos={self.get_success(from_token.to_string(self.store))}",
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        # Large enough to see the latest events and before the invite
+                        "timeline_limit": 4,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # `timeline` is omitted for `invite` rooms with `stripped_state`
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("timeline"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `num_live` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("num_live"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `limited` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("limited"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # `prev_batch` is omitted for `invite` rooms with `stripped_state` (no timeline anyway)
+        self.assertIsNone(
+            channel.json_body["rooms"][room_id1].get("prev_batch"),
+            channel.json_body["rooms"][room_id1],
+        )
+        # We should have some `stripped_state` so the potential joiner can identify the
+        # room (we don't care about the order).
+        self.assertCountEqual(
+            channel.json_body["rooms"][room_id1]["invite_state"],
+            [
+                {
+                    "content": {"creator": user2_id, "room_version": "10"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.create",
+                },
+                {
+                    "content": {"join_rule": "public"},
+                    "sender": user2_id,
+                    "state_key": "",
+                    "type": "m.room.join_rules",
+                },
+                {
+                    "content": {"displayname": user2.localpart, "membership": "join"},
+                    "sender": user2_id,
+                    "state_key": user2_id,
+                    "type": "m.room.member",
+                },
+                {
+                    "content": {"displayname": user1.localpart, "membership": "invite"},
+                    "sender": user2_id,
+                    "state_key": user1_id,
+                    "type": "m.room.member",
+                },
+            ],
+            channel.json_body["rooms"][room_id1]["invite_state"],
+        )
+
+    def test_rooms_ban_initial_sync(self) -> None:
+        """
+        Test that `rooms` we are banned from in an intial sync only allows us to see
+        timeline events up to the ban event.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity before1", tok=user2_tok)
+        self.helper.send(room_id1, "activity before2", tok=user2_tok)
+        self.helper.join(room_id1, user1_id, tok=user1_tok)
+
+        event_response3 = self.helper.send(room_id1, "activity after3", tok=user2_tok)
+        event_response4 = self.helper.send(room_id1, "activity after4", tok=user2_tok)
+        user1_ban_response = self.helper.ban(
+            room_id1, src=user2_id, targ=user1_id, tok=user2_tok
+        )
+
+        self.helper.send(room_id1, "activity after5", tok=user2_tok)
+        self.helper.send(room_id1, "activity after6", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint,
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": 3,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # We should see events before the ban but not after
+        self.assertEqual(
+            [
+                event["event_id"]
+                for event in channel.json_body["rooms"][room_id1]["timeline"]
+            ],
+            [
+                event_response3["event_id"],
+                event_response4["event_id"],
+                user1_ban_response["event_id"],
+            ],
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+        # No "live" events in an initial sync (no `from_token` to define the "live"
+        # range)
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            0,
+            channel.json_body["rooms"][room_id1],
+        )
+        # There are more events to paginate to
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            True,
+            channel.json_body["rooms"][room_id1],
+        )
+
+    def test_rooms_ban_incremental_sync1(self) -> None:
+        """
+        Test that `rooms` we are banned from during the next incremental sync only
+        allows us to see timeline events up to the ban event.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity before1", tok=user2_tok)
+        self.helper.send(room_id1, "activity before2", tok=user2_tok)
+        self.helper.join(room_id1, user1_id, tok=user1_tok)
+
+        from_token = self.event_sources.get_current_token()
+
+        event_response3 = self.helper.send(room_id1, "activity after3", tok=user2_tok)
+        event_response4 = self.helper.send(room_id1, "activity after4", tok=user2_tok)
+        # The ban is within the token range (between the `from_token` and the sliding
+        # sync request)
+        user1_ban_response = self.helper.ban(
+            room_id1, src=user2_id, targ=user1_id, tok=user2_tok
+        )
+
+        self.helper.send(room_id1, "activity after5", tok=user2_tok)
+        self.helper.send(room_id1, "activity after6", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint
+            + f"?pos={self.get_success(from_token.to_string(self.store))}",
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": 4,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # We should see events before the ban but not after
+        self.assertEqual(
+            [
+                event["event_id"]
+                for event in channel.json_body["rooms"][room_id1]["timeline"]
+            ],
+            [
+                event_response3["event_id"],
+                event_response4["event_id"],
+                user1_ban_response["event_id"],
+            ],
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+        # All live events in the incremental sync
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            3,
+            channel.json_body["rooms"][room_id1],
+        )
+        # There aren't anymore events to paginate to in this range
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            False,
+            channel.json_body["rooms"][room_id1],
+        )
+
+    def test_rooms_ban_incremental_sync2(self) -> None:
+        """
+        Test that `rooms` we are banned from before the incremental sync don't return
+        any events in the timeline.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        room_id1 = self.helper.create_room_as(user2_id, tok=user2_tok)
+        self.helper.send(room_id1, "activity before1", tok=user2_tok)
+        self.helper.join(room_id1, user1_id, tok=user1_tok)
+
+        self.helper.send(room_id1, "activity after2", tok=user2_tok)
+        # The ban is before we get our `from_token`
+        self.helper.ban(room_id1, src=user2_id, targ=user1_id, tok=user2_tok)
+
+        self.helper.send(room_id1, "activity after3", tok=user2_tok)
+
+        from_token = self.event_sources.get_current_token()
+
+        self.helper.send(room_id1, "activity after4", tok=user2_tok)
+
+        # Make the Sliding Sync request
+        channel = self.make_request(
+            "POST",
+            self.sync_endpoint
+            + f"?pos={self.get_success(from_token.to_string(self.store))}",
+            {
+                "lists": {
+                    "foo-list": {
+                        "ranges": [[0, 1]],
+                        "required_state": [],
+                        "timeline_limit": 4,
+                    }
+                }
+            },
+            access_token=user1_tok,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+
+        # Nothing to see for this banned user in the room in the token range
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["timeline"],
+            [],
+            channel.json_body["rooms"][room_id1]["timeline"],
+        )
+        # No events returned in the timeline so nothing is "live"
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["num_live"],
+            0,
+            channel.json_body["rooms"][room_id1],
+        )
+        # There aren't anymore events to paginate to in this range
+        self.assertEqual(
+            channel.json_body["rooms"][room_id1]["limited"],
+            False,
+            channel.json_body["rooms"][room_id1],
+        )
diff --git a/tests/rest/client/utils.py b/tests/rest/client/utils.py
index f0ba40a1f1..e43140720d 100644
--- a/tests/rest/client/utils.py
+++ b/tests/rest/client/utils.py
@@ -261,9 +261,9 @@ class RestHelper:
         targ: str,
         expect_code: int = HTTPStatus.OK,
         tok: Optional[str] = None,
-    ) -> None:
+    ) -> JsonDict:
         """A convenience helper: `change_membership` with `membership` preset to "ban"."""
-        self.change_membership(
+        return self.change_membership(
             room=room,
             src=src,
             targ=targ,