Rooms with unsupported versions are shown as blank rooms

[ara4n]

In the last ~4-5 days

!VXChyxVNCBsWeSGcaN:sw1v.org
!eKTrlepAvBEhUIyoQV:jki.re
!bNAPsppHlSHCDvMRhh:abolivier.bzh

[ara4n]

(i haven't actually looked at my /sync response, but riot shows them to be entirely blank v1 rooms)

[neilisfragile]

I also can't see !eKTrlepAvBEhUIyoQV:jki.re

[erikjohnston]

All three of those rooms use experimental room versions that have since been removed from synapse, I think its basically expected for those to go pop, though they should go pop in a better way.

[neilisfragile]

Right and it just about works okay when people have cached history, but switching over to a new client (like Riot electron) has this problem.

[richvdh]

I'm going to suggest we triage this alongside other synapse bugs rather than treat it as a crisis.

[clokep]

#7209 also points to some errors during initial sync for unknown room versions.

[richvdh]

suggestion is that for now we exclude such rooms from initial /sync responses, thus hiding them on clients. (you'll have to flush your client cache, but we can live with that)

In future, if we drop production room versions (eg v1) we'll need to do better than this, but this will do as a first step.

[ara4n]

how do I get back into these rooms, though? i can't seem to participate in them enough to follow the tombstone to the new version...

[richvdh]

you don't. The whole point is that they were experimental room versions that are no longer supported. I guess you get someone to manually invite you to the new room.

[anoadragon453]

Worth noting that deleting the room from rooms and the events from events and events_json clears them right up.

[erikjohnston]

Currently /purge_rooms fails to delete these rooms, as users are in them. Might be worth fixing it so that it works?

[jryans]

Personally, I would at least like to be able to leave these unsupported rooms, but currently even that is not possible... 😢

Currently, the /leave request gives a 400 error with M_UNSUPPORTED_ROOM_VERSION. The unfortunate symptom of this is that the unleavable room is permanently at the top of my room list... 😭

[clokep]

Personally, I would at least like to be able to leave these unsupported rooms, but currently even that is not possible... 😢

The technical reason behind this is that Synapse doesn't know how to resolve state in those rooms.

[anoadragon453]

Can we just generate a local out-of-band leave event for the client, just as we do when rejecting an invite/rescinding a knock from a room that we're not in and cannot contact?

synapse/synapse/handlers/room_member.py

Lines 1404 to 1425 in 96f6293

	async def _generate_local_out_of_band_leave(
	self,
	previous_membership_event: EventBase,
	txn_id: Optional[str],
	requester: Requester,
	content: JsonDict,
	) -> Tuple[str, int]:
	"""Generate a local leave event for a room
	This can be called after we e.g fail to reject an invite via a remote server.
	It generates an out-of-band membership event locally.
	Args:
	previous_membership_event: the previous membership event for this user
	txn_id: optional transaction ID supplied by the client
	requester: user making the request, according to the access token
	content: additional content to include in the leave event.
	Normally an empty dict.
	Returns:
	A tuple containing (event_id, stream_id of the leave event)
	"""

It just generates a leave event that's propagated to the client, but not into the room proper.

[richvdh]

even out-of-band leaves go through state res...

[richvdh]

I think? maybe not, actually. Might be worth a go. (but then, I still think it would be easier just to exclude unsupported rooms from /sync.)

[clokep]

I think? maybe not, actually. Might be worth a go. (but then, I still think it would be easier just to exclude unsupported rooms from /sync.)

I'm fairly certain they do, we still generate an event which requires a known room version (and it also requires auth/prev events).