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fix(sync/v3): Add a workaround for matrix-js-sdk/5071

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This commit is contained in:
Ginger 2025-11-06 10:02:27 -05:00
parent d2cc2fb19b
commit 852bf99d34
1 changed files with 36 additions and 4 deletions
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40
src/api/client/sync/v3/left.rs
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@ -65,8 +65,6 @@ pub(super) async fn load_left_room(
return Ok(None);
};
let include_leave = filter.room.include_leave;
// return early if we haven't gotten to this leave yet.
// this can happen if the user leaves while a sync response is being generated
if current_count < left_count {
@ -75,7 +73,7 @@ pub(super) async fn load_left_room(
// return early if this is an incremental sync, and we've already synced this
// leave to the user, and `include_leave` isn't set on the filter.
if !include_leave && last_sync_end_count >= Some(left_count) {
if !filter.room.include_leave && last_sync_end_count >= Some(left_count) {
return Ok(None);
}
@ -110,6 +108,8 @@ pub(super) async fn load_left_room(
"leave PDU should be for the user requesting the sync"
);
// the shortstatehash of the state _immediately before_ the syncing user left
// this room. the state represented here _does not_ include `leave_pdu`.
let leave_shortstatehash = services
.rooms
.state_accessor
@ -190,6 +190,9 @@ pub(super) async fn load_left_room(
}
}
// the timeline generally should not be empty (see the TODO further down),
// but in case it is we use `leave_shortstatehash` as the state to
// send
leave_shortstatehash
};
@ -206,7 +209,7 @@ pub(super) async fn load_left_room(
// TODO: calculate incremental state for incremental syncs.
// always calculating initial state _works_ but returns more data and does
// more processing than strictly necessary.
let state = build_state_initial(
let mut state = build_state_initial(
services,
syncing_user,
timeline_start_shortstatehash,
@ -214,6 +217,35 @@ pub(super) async fn load_left_room(
)
.await?;
/*
remove membership events for the syncing user from state.
usually, `state` should include a `join` membership event and `timeline` should include a `leave` one.
however, the matrix-js-sdk gets confused when this happens (see [1]) and doesn't process the room leave,
so we have to filter out the membership from `state`.
NOTE: we are sending more information than synapse does in this scenario, because we always
calculate `state` for initial syncs, even when the sync being performed is incremental.
however, the specification does not forbid sending extraneous events in `state`.
TODO: there is an additional bug at play here. sometimes `load_joined_room` syncs the `leave` event
before `load_left_room` does, which means the `timeline` we sync immediately after a leave is empty.
this shouldn't happen -- `timeline` should always include the `leave` event. this is probably
a race condition with the membership state cache.
[1]: https://github.com/matrix-org/matrix-js-sdk/issues/5071
*/
// `state` should only ever include one membership event for the syncing user
let membership_event_index = state.iter().position(|pdu| {
*pdu.event_type() == TimelineEventType::RoomMember
&& pdu.state_key() == Some(syncing_user.as_str())
});
if let Some(index) = membership_event_index {
// the ordering of events in `state` does not matter
state.swap_remove(index);
}
trace!(
?timeline_start_count,
?timeline_end_count,