Incorrect and unclear description of prev_batch usage for /sync

[joepie91]

From the spec:

Finally, the response includes, for each room, a prev_batch field, which can be passed as a start parameter to the /rooms/<room_id>/messages API to retrieve earlier messages.
[...]
prev_batch: A token that can be supplied to the from parameter of the rooms/{roomId}/messages endpoint.

Two issues with this:

1. It's not clearly defined what dir one should request from /messages, using this prev_batch token
2. There is no such thing as a start parameter, like the first part of the quoted text claims (there's only such a property in the response); presumably, that was supposed to say from rather than start.

[turt2live]

I think this is largely a duplicate of matrix-org/matrix-spec-proposals#2420, though anything not mentioned there can be merged into the comments section.

[joepie91]

That's definitely a different issue; neither of these two issues are mentioned there, and that issue concerns the documentation for the /messages endpoint itself whereas this one concerns the documentation for /sync.

Not sure if you want them merged anyway, but it's definitely not a duplicate :)

[turt2live]

ah, indeed. Nowhere in your issue did it say this was was sync, but all the words show up in the backfill endpoints.

[joepie91]

Ah right, I probably should've mentioned that explicitly. Apologies.