From bb3566a64933306c999947d3120c6dd2245e23d5 Mon Sep 17 00:00:00 2001
From: Till Faelligen <2353100+S7evinK@users.noreply.github.com>
Date: Tue, 11 Jul 2023 11:21:07 +0200
Subject: [PATCH] Return r.from instead of an empty token

---
 syncapi/routing/messages.go     | 12 ++++++------
 syncapi/storage/storage_test.go |  3 ++-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/syncapi/routing/messages.go b/syncapi/routing/messages.go
index 361581230..6905e25c7 100644
--- a/syncapi/routing/messages.go
+++ b/syncapi/routing/messages.go
@@ -336,10 +336,10 @@ func (r *messagesReq) retrieveEvents(ctx context.Context, rsAPI api.SyncRoomserv
 		// removed all of them. This means there are no events for this user
 		// anymore. Let them know.
 		if errors.Is(err, shared.ErrNoEventsForFilter) {
-			return []synctypes.ClientEvent{}, emptyToken, emptyToken, nil
+			return []synctypes.ClientEvent{}, *r.from, emptyToken, nil
 		}
 		err = fmt.Errorf("GetEventsInRange: %w", err)
-		return []synctypes.ClientEvent{}, emptyToken, emptyToken, err
+		return []synctypes.ClientEvent{}, *r.from, emptyToken, err
 	}
 
 	var events []*rstypes.HeaderedEvent
@@ -354,17 +354,17 @@ func (r *messagesReq) retrieveEvents(ctx context.Context, rsAPI api.SyncRoomserv
 	// on the ordering), or we've reached a backward extremity.
 	if len(streamEvents) == 0 {
 		if events, err = r.handleEmptyEventsSlice(); err != nil {
-			return []synctypes.ClientEvent{}, emptyToken, emptyToken, err
+			return []synctypes.ClientEvent{}, *r.from, emptyToken, err
 		}
 	} else {
 		if events, err = r.handleNonEmptyEventsSlice(streamEvents); err != nil {
-			return []synctypes.ClientEvent{}, emptyToken, emptyToken, err
+			return []synctypes.ClientEvent{}, *r.from, emptyToken, err
 		}
 	}
 
 	// If we didn't get any event, we don't need to proceed any further.
 	if len(events) == 0 {
-		return []synctypes.ClientEvent{}, emptyToken, emptyToken, nil
+		return []synctypes.ClientEvent{}, *r.from, emptyToken, nil
 	}
 
 	// Apply room history visibility filter
@@ -382,7 +382,7 @@ func (r *messagesReq) retrieveEvents(ctx context.Context, rsAPI api.SyncRoomserv
 
 	// No events left after applying history visibility
 	if len(filteredEvents) == 0 {
-		return []synctypes.ClientEvent{}, emptyToken, emptyToken, nil
+		return []synctypes.ClientEvent{}, *r.from, emptyToken, nil
 	}
 
 	// Get the position of the first and the last event in the room's topology.
diff --git a/syncapi/storage/storage_test.go b/syncapi/storage/storage_test.go
index 11d47cee7..a4eb9412a 100644
--- a/syncapi/storage/storage_test.go
+++ b/syncapi/storage/storage_test.go
@@ -224,7 +224,8 @@ func TestGetEventsInRangeWithTopologyToken(t *testing.T) {
 	})
 }
 
-// The purpose of this test is to ensure that backfill does indeed go backwards, using a topology token
+// The purpose of this test is to ensure that backfilling returns no start/end if a given filter removes
+// all events.
 func TestGetEventsInRangeWithTopologyTokenNoEventsForFilter(t *testing.T) {
 	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
 		db, close := MustCreateDatabase(t, dbType)