Leave event missing from state_after #18793
Description
Description
When a client leaves a room on a homeserver where matrix-org/matrix-spec-proposals#4222 is enabled, the leave event doesn't appear in the state_after (or org.matrix.msc4222.state_after). I believe it should do because state_after should duplicate all state events from the timeline section that apply at the end of the point the sync covers.
Response from beta.matrix.org (with MSC4222 enabled):
"leave": {
"!CdHcMUhjzlGJQr299cjiQZgJNFdQtmAUJlIamKQ7pvg": {
"timeline": {
"events": [
{
"type": "m.room.member",
"sender": "@davetest:beta.matrix.org",
"content": {
"membership": "leave"
},
"state_key": "@davetest:beta.matrix.org",
"origin_server_ts": 1754658410215,
"unsigned": {
"replaces_state": "$gORoiLnG_h2mWrKoW4jhjvvXGFj39ReLdV-fq4w4bOc",
"prev_content": {
"displayname": "dave test",
"membership": "join"
},
"prev_sender": "@davetest:beta.matrix.org",
"membership": "leave",
"age": 120
},
"event_id": "$WseXqR8u9P9M2tpf7wahk_QmEp1ogJexRLL41HS5iAs"
}
],
"prev_batch": "s4436051_1_9238_3990099_16270_238_38684_2677914_0_340",
"limited": false
},
"org.matrix.msc4222.state_after": {
"events": []
},
"account_data": {
"events": []
}
}
}
Note that the leave event is in the timeline section but not in state_after.
From matrix.org (without MSC4222):
"leave": {
"!QnwqAqEkZlreqGleJe:matrix.org": {
"timeline": {
"events": [
{
"content": {
"membership": "leave"
},
"origin_server_ts": 1754658946055,
"sender": "@dave:matrix.org",
"state_key": "@dave:matrix.org",
"type": "m.room.member",
"unsigned": {
"replaces_state": "$xDKAUL61qiMbA6-5ABYRuHEqy5UhCUfrhZk0xTDjzS8",
"prev_content": {
"avatar_url": "mxc://matrix.org/IssHdyiXMcSnRCxCzqoaocGL",
"displayname": "Dave",
"membership": "join"
},
"prev_sender": "@dave:matrix.org",
"membership": "leave",
"age": 1724
},
"event_id": "$H456wIzEatLxS5chZ7aN72E-JkN0XCuQq9bb1XlqLHE"
}
],
"prev_batch": "s6158096937_757284974_4199159_m3882099430~39.3882099443~72.3882099441~38.3882099445_4412080234_266497694_1516505502_11171079150_0_521298",
"limited": false
},
"state": {
"events": [
{
"content": {
"membership": "leave"
},
"origin_server_ts": 1754658946055,
"sender": "@dave:matrix.org",
"state_key": "@dave:matrix.org",
"type": "m.room.member",
"unsigned": {
"replaces_state": "$xDKAUL61qiMbA6-5ABYRuHEqy5UhCUfrhZk0xTDjzS8",
"prev_content": {
"avatar_url": "mxc://matrix.org/IssHdyiXMcSnRCxCzqoaocGL",
"displayname": "Dave",
"membership": "join"
},
"prev_sender": "@dave:matrix.org",
"age": 1724
},
"event_id": "$H456wIzEatLxS5chZ7aN72E-JkN0XCuQq9bb1XlqLHE"
}
]
},
"account_data": {
"events": []
}
}
}
...which is also somewhat odd in that I wouldn't expect the leave event to be in the state block because in non-msc4222 mode, state events in the timeline block are added to state and don't need to be duplicated, so that's fun. It's not really what this bug is about, but included for context nonetheless.
This causes rooms to not appear as if the user has left them on clients when using MSC4222.
Steps to reproduce
- Enable MSC4222 in synapse and find a client that supports it (or sync using
org.matrix.msc4222.use_state_after=true) - Leave a room
Homeserver
beta.matrix.org
Synapse Version
1.134.0
Installation Method
I don't know
Database
Unknown
Workers
I don't know
Platform
EMS?
Configuration
No response
Relevant log output
NoneAnything else that would be useful to know?
No response