fix(hydra): Unable to parse backfilled incoming create events

src/api/client/membership/join.rs

@@ -604,6 +604,7 @@ async fn join_room_by_id_helper_remote(
 		})
 		.ready_filter_map(Result::ok)
 		.ready_for_each(|(event_id, value)| {
+			trace!(%event_id, "Adding PDU as an outlier from send_join auth_chain");
 			services.rooms.outlier.add_pdu_outlier(&event_id, &value);
 		})
 		.await;
@@ -661,7 +662,7 @@ async fn join_room_by_id_helper_remote(
 		.force_state(room_id, statehash_before_join, added, removed, &state_lock)
 		.await?;
 
-	info!("Updating joined counts for new room");
+	debug!("Updating joined counts for new room");
 	services
 		.rooms
 		.state_cache

src/service/rooms/event_handler/parse_incoming_pdu.rs

@@ -1,7 +1,8 @@
 use conduwuit::{
-	Result, err, implement, matrix::event::gen_event_id_canonical_json, result::FlatOk,
+	Result, RoomVersion, err, implement, matrix::event::gen_event_id_canonical_json,
+	result::FlatOk,
 };
-use ruma::{CanonicalJsonObject, CanonicalJsonValue, OwnedEventId, OwnedRoomId};
+use ruma::{CanonicalJsonObject, CanonicalJsonValue, OwnedEventId, OwnedRoomId, RoomVersionId};
 use serde_json::value::RawValue as RawJsonValue;
 
 type Parsed = (OwnedRoomId, OwnedEventId, CanonicalJsonObject);
@@ -11,12 +12,44 @@ pub async fn parse_incoming_pdu(&self, pdu: &RawJsonValue) -> Result<Parsed> {
 	let value = serde_json::from_str::<CanonicalJsonObject>(pdu.get()).map_err(|e| {
 		err!(BadServerResponse(debug_warn!("Error parsing incoming event {e:?}")))
 	})?;
-
-	let room_id: OwnedRoomId = value
-		.get("room_id")
+	let event_type = value
+		.get("type")
 		.and_then(CanonicalJsonValue::as_str)
-		.map(OwnedRoomId::parse)
-		.flat_ok_or(err!(Request(InvalidParam("Invalid room_id in pdu"))))?;
+		.ok_or_else(|| err!(Request(InvalidParam("Missing or invalid type in pdu"))))?;
+
+	let room_id: OwnedRoomId = if event_type != "m.room.create" {
+		value
+			.get("room_id")
+			.and_then(CanonicalJsonValue::as_str)
+			.map(OwnedRoomId::parse)
+			.flat_ok_or(err!(Request(InvalidParam("Invalid room_id in pdu"))))?
+	} else {
+		// v12 rooms might have no room_id in the create event. We'll need to check the
+		// content.room_version
+		let content = value
+			.get("content")
+			.and_then(CanonicalJsonValue::as_object)
+			.ok_or_else(|| err!(Request(InvalidParam("Missing or invalid content in pdu"))))?;
+		let room_version = content
+			.get("room_version")
+			.and_then(CanonicalJsonValue::as_str)
+			.unwrap_or("1");
+		let vi = RoomVersionId::try_from(room_version).unwrap_or(RoomVersionId::V1);
+		let vf = RoomVersion::new(&vi).expect("supported room version");
+		if vf.room_ids_as_hashes {
+			let (event_id, _) = gen_event_id_canonical_json(pdu, &vi).map_err(|e| {
+				err!(Request(InvalidParam("Could not convert event to canonical json: {e}")))
+			})?;
+			OwnedRoomId::parse(event_id.as_str().replace('$', "!")).expect("valid room ID")
+		} else {
+			// V11 or below room, room_id must be present
+			value
+				.get("room_id")
+				.and_then(CanonicalJsonValue::as_str)
+				.map(OwnedRoomId::parse)
+				.flat_ok_or(err!(Request(InvalidParam("Invalid or missing room_id in pdu"))))?
+		}
+	};
 
 	let room_version_id = self
 		.services
@@ -24,10 +57,8 @@ pub async fn parse_incoming_pdu(&self, pdu: &RawJsonValue) -> Result<Parsed> {
 		.get_room_version(&room_id)
 		.await
 		.map_err(|_| err!("Server is not in room {room_id}"))?;
-
 	let (event_id, value) = gen_event_id_canonical_json(pdu, &room_version_id).map_err(|e| {
 		err!(Request(InvalidParam("Could not convert event to canonical json: {e}")))
 	})?;
-
 	Ok((room_id, event_id, value))
 }

src/service/rooms/timeline/backfill.rs

@@ -38,6 +38,7 @@ pub async fn backfill_if_required(&self, room_id: &RoomId, from: PduCount) -> Re
 			.await
 	{
 		// Room is empty (1 user or none), there is no one that can backfill
+		debug_warn!("Room {room_id} is empty, skipping backfill");
 		return Ok(());
 	}
 
@@ -48,6 +49,7 @@ pub async fn backfill_if_required(&self, room_id: &RoomId, from: PduCount) -> Re
 
 	if first_pdu.0 < from {
 		// No backfill required, there are still events between them
+		debug!("No backfill required in room {room_id}, {:?} < {from}", first_pdu.0);
 		return Ok(());
 	}