fix: tree diff calc children should be sorted by idlp (#401)

crates/fuzz/src/actor.rs

@@ -161,6 +161,12 @@ impl Actor {
     }
 
     pub fn check_history(&mut self) {
+        // let json = self
+        //     .loro
+        //     .export_json_updates(&Default::default(), &self.loro.oplog_vv());
+        // let string = serde_json::to_string_pretty(&json).unwrap();
+        // tracing::info!("json = {}", string);
+
         for (f, v) in self.history.iter() {
             let f = Frontiers::from(f);
             let from = &self.loro.state_frontiers();

crates/loro-internal/src/diff_calc/tree.rs

@@ -449,7 +449,12 @@ impl TreeCacheForDiff {
                 ans.push((*tree_id, op.position.clone(), op.id_full()));
             }
         }
-        ans.sort_by(|a, b| a.1.cmp(&b.1));
+        // The children should be sorted by the position.
+        // If the fractional index is the same, then sort by the lamport and peer.
+        ans.sort_by(|a, b| {
+            a.1.cmp(&b.1)
+                .then(a.2.lamport.cmp(&b.2.lamport).then(a.2.peer.cmp(&b.2.peer)))
+        });
         ans
     }
 }