/messages endpoint returns end token identical to from token

[johannescpk]

Description

Goal is to fetch messages in a room backwards.

Steps to reproduce

• My client first does a /sync to get the latest next_batch token
• I'm then using that token to pass it into the messages endpoint as { from: $next_batch, direction: "b", .. }.
• The response from the server has an end field that's the same as the next_batch token that was used in the initial request, additionally to all room messages.

So it seems there's an issue with synapse not leaving the end token empty if it reaches the end of the timeline.

For reference, here's the raw response from synapse, where start and end are identical.

matrix_sdk::http_client: Got response: Response { status: 200, version: HTTP/1.1, headers: {"transfer-encoding": "chunked", "server": "Synapse/1.53.0", "date": "Mon, 28 Feb 2022 14:45:37 GMT", "content-type": "application/json", "cache-control": "no-cache, no-store, must-revalidate", "access-control-allow-origin": "*", "access-control-allow-methods": "GET, HEAD, POST, PUT, DELETE, OPTIONS", "access-control-allow-headers": "X-Requested-With, Content-Type, Authorization, Date"}, body: b"{"chunk":[],"start":"t1-915_1917_28_2_75_1_1_77_1","end":"t1-915_1917_28_2_75_1_1_77_1"}" }

Version information

• Homeserver: Local dev instance

If not matrix.org:

• Version: 1.53.0

• Install method: docker hub

• Platform: x86 64bit, docker container

[richvdh]

I find it amazing that we don't have an issue for this already, but I don't think we do.

It was discussed at matrix-org/matrix-spec-proposals#2251 (comment), but there doesn't appear to have been an issue filed.

[richvdh]

I'd be happy to see a PR that fixes this.