work around bug in ruma::state_res::resolve

src/cli/repair.rs

@@ -18,7 +18,9 @@ use petgraph::{
 };
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use ruma::{
-    events::{room::member::MembershipState, StateEventType},
+    events::{
+        room::member::MembershipState, StateEventType, TimelineEventType,
+    },
     state_res::StateMap,
     EventId, RoomId, RoomVersionId, UserId,
 };
@@ -441,8 +443,26 @@ fn get_state_event_graphs(
                 return None;
             };
 
+            let Some(state_key) = pdu.state_key else {
                 // Filter out non-state events
-            pdu.state_key?;
+                return None;
+            };
+
+            // Ruma fails the entire state resolution if it sees an event whose
+            // `state_key` it needs to parse as an ID and the parsing fails, so
+            // we pre-emptively drop these events. Real-world cases where this
+            // has happened are detailed on the issue linked below.
+            //
+            // <https://github.com/ruma/ruma/issues/1944>
+            if pdu.kind == TimelineEventType::RoomMember
+                && <&UserId>::try_from(&*state_key).is_err()
+            {
+                t::warn!(
+                    event_id = %pdu.event_id,
+                    "Dropping event that could cause state resolution to fail",
+                );
+                return None;
+            }
 
             Some((
                 <Arc<RoomId>>::from(pdu.room_id),