From f6c74d1cb2ed966802b01a2b037f09ce7a842c18 Mon Sep 17 00:00:00 2001
From: Benjamin Kampmann <ben.kampmann@gmail.com>
Date: Thu, 24 Nov 2022 09:10:51 +0000
Subject: Implement message forward pagination from start when no from is
 given, fixes #12383 (#14149)

Fixes https://github.com/matrix-org/synapse/issues/12383
---
 synapse/handlers/pagination.py |  6 ++++++
 synapse/streams/events.py      | 13 +++++++++++++
 2 files changed, 19 insertions(+)

(limited to 'synapse')

diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index a4ca9cb8b4..c572508a02 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -448,6 +448,12 @@ class PaginationHandler:
 
         if pagin_config.from_token:
             from_token = pagin_config.from_token
+        elif pagin_config.direction == "f":
+            from_token = (
+                await self.hs.get_event_sources().get_start_token_for_pagination(
+                    room_id
+                )
+            )
         else:
             from_token = (
                 await self.hs.get_event_sources().get_current_token_for_pagination(
diff --git a/synapse/streams/events.py b/synapse/streams/events.py
index f331e1af16..619eb7f601 100644
--- a/synapse/streams/events.py
+++ b/synapse/streams/events.py
@@ -73,6 +73,19 @@ class EventSources:
         )
         return token
 
+    @trace
+    async def get_start_token_for_pagination(self, room_id: str) -> StreamToken:
+        """Get the start token for a given room to be used to paginate
+        events.
+
+        The returned token does not have the current values for fields other
+        than `room`, since they are not used during pagination.
+
+        Returns:
+            The start token for pagination.
+        """
+        return StreamToken.START
+
     @trace
     async def get_current_token_for_pagination(self, room_id: str) -> StreamToken:
         """Get the current token for a given room to be used to paginate
-- 
cgit 1.5.1