fix: Opportunistically re-use room format rules when parsing incoming PDUs

src/service/rooms/event_handler/fetch_and_handle_outliers.rs

@@ -241,7 +241,7 @@ impl super::Service {
 
 			latest_events.clear();
 			for raw_event in response.events {
-				let (_, event_id, pdu_json) = self.parse_incoming_pdu(&raw_event).await?;
+				let (_, event_id, pdu_json) = self.parse_incoming_pdu(&raw_event, None).await?;
 				let pdu = PduEvent::from_id_val(&event_id, pdu_json).map_err(|e| {
 					err!(Request(BadJson("Failed to parse gapfilled event {event_id}: {e}")))
 				})?;
@@ -384,8 +384,9 @@ impl super::Service {
 			.send_federation_request(&remote, get_event::v1::Request::new(event_id.clone()))
 			.await?;
 
-		let (calculated_event_id, value) =
-			Self::parse_incoming_pdu_with_known_room(&res.pdu, room_version_rules)?;
+		let (_, calculated_event_id, value) = self
+			.parse_incoming_pdu(&res.pdu, Some(room_version_rules))
+			.await?;
 
 		if calculated_event_id != event_id {
 			Err!(Request(BadJson(warn!(

src/service/rooms/event_handler/fetch_auth.rs

@@ -48,14 +48,16 @@ impl super::Service {
 		let mut auth_chain_map = HashMap::with_capacity(event_auth.auth_chain.len());
 
 		for auth_pdu_json in event_auth.auth_chain {
-			let (auth_event_room_id, auth_event_id, auth_pdu_json) =
-				match self.parse_incoming_pdu(&auth_pdu_json).await {
-					| Ok(parsed) => parsed,
-					| Err(e) => {
-						warn!(error=?e, "Dropping auth chain event as it could not be parsed");
-						continue;
-					},
-				};
+			let (auth_event_room_id, auth_event_id, auth_pdu_json) = match self
+				.parse_incoming_pdu(&auth_pdu_json, Some(room_version_rules))
+				.await
+			{
+				| Ok(parsed) => parsed,
+				| Err(e) => {
+					warn!(error=?e, "Dropping auth chain event as it could not be parsed");
+					continue;
+				},
+			};
 			if let Err(e) = Self::pdu_format_check_1(
 				&auth_pdu_json,
 				room_version_rules,

src/service/rooms/event_handler/fetch_state.rs

@@ -314,7 +314,7 @@ impl super::Service {
 			.iter()
 			.stream()
 			.broad_filter_map(|raw_event_json| async {
-				if let Some(parsed) = self.parse_incoming_pdu(raw_event_json).await.ok()
+				if let Some(parsed) = self.parse_incoming_pdu(raw_event_json, None).await.ok()
 					&& parsed.0 == room_id
 				{
 					Some(parsed)
@@ -351,7 +351,7 @@ impl super::Service {
 			.iter()
 			.stream()
 			.broad_filter_map(|raw_event_json| async {
-				if let Some(parsed) = self.parse_incoming_pdu(raw_event_json).await.ok()
+				if let Some(parsed) = self.parse_incoming_pdu(raw_event_json, None).await.ok()
 					&& parsed.0 == room_id
 				{
 					Some(parsed)

src/service/rooms/event_handler/parse_incoming_pdu.rs

@@ -82,25 +82,14 @@ pub(super) fn expect_event_id_array(
 }
 
 impl super::Service {
-	/// Parses an incoming PDU JSON object, generating an event ID for it. Does
-	/// not insert the event ID into the returned object. Does not discover the
-	/// room ID.
-	pub(super) fn parse_incoming_pdu_with_known_room(
-		pdu: &RawJsonValue,
-		room_version_rules: &RoomVersionRules,
-	) -> Result<(OwnedEventId, CanonicalJsonObject)> {
-		let (event_id, value) =
-			gen_event_id_canonical_json(pdu, room_version_rules).map_err(|e| {
-				err!(Request(InvalidParam("Could not convert event to canonical json: {e}")))
-			})?;
-		// NOTE: validation checks are now performed by `pdu_format_check_1`.
-		Ok((event_id, value))
-	}
-
 	/// Parses an incoming PDU JSON object, generating an event ID for it and
 	/// attempts to discover the associated room ID. Does not insert the event
 	/// ID into the returned object.
-	pub async fn parse_incoming_pdu(&self, pdu: &RawJsonValue) -> Result<Parsed> {
+	pub async fn parse_incoming_pdu(
+		&self,
+		pdu: &RawJsonValue,
+		room_version_rules: Option<&RoomVersionRules>,
+	) -> Result<Parsed> {
 		let value = serde_json::from_str::<CanonicalJsonObject>(pdu.get()).map_err(|e| {
 			err!(BadServerResponse(debug_warn!("Error parsing incoming event {e:?}")))
 		})?;
@@ -111,17 +100,20 @@ impl super::Service {
 
 		let room_id = extract_room_id(event_type, &value)?;
 
-		let room_version_rules = self
-			.services
-			.state
-			.get_room_version(&room_id)
-			.await
-			.unwrap_or(RoomVersionId::V1)
-			.rules()
-			.unwrap();
+		let room_version_rules = match room_version_rules {
+			| Some(r) => r,
+			| None => &self
+				.services
+				.state
+				.get_room_version(&room_id)
+				.await
+				.unwrap_or(RoomVersionId::V1)
+				.rules()
+				.unwrap(),
+		};
 
 		let (event_id, value) =
-			gen_event_id_canonical_json(pdu, &room_version_rules).map_err(|e| {
+			gen_event_id_canonical_json(pdu, room_version_rules).map_err(|e| {
 				err!(Request(InvalidParam("Could not convert event to canonical json: {e}")))
 			})?;
 		// NOTE: validation checks are now performed by `pdu_format_check_1`.

src/service/rooms/timeline/backfill.rs

@@ -166,8 +166,11 @@ impl super::Service {
 	/// Backfills a single PDU.
 	#[tracing::instrument(skip(self, pdu), level = "debug")]
 	pub async fn backfill_pdu(&self, origin: &ServerName, pdu: Box<RawJsonValue>) -> Result<()> {
-		let (room_id, event_id, value) =
-			self.services.event_handler.parse_incoming_pdu(&pdu).await?;
+		let (room_id, event_id, value) = self
+			.services
+			.event_handler
+			.parse_incoming_pdu(&pdu, None)
+			.await?;
 
 		// Lock so we cannot backfill the same pdu twice at the same time
 		let mutex_lock = self