draft: the problem is in _list_renderer.py

music_kraken/objects/collection.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections import defaultdict
-from typing import TypeVar, Generic, Dict, Optional, Iterable, List, Iterator, Tuple, Generator, Union, Any
+from typing import TypeVar, Generic, Dict, Optional, Iterable, List, Iterator, Tuple, Generator, Union, Any, Set
 from .parents import OuterProxy
 from ..utils import object_trace
 
@@ -117,14 +117,26 @@ class Collection(Generic[T]):
                 if a is b:
                     continue
 
-                object_trace(f"Syncing [{a}] = [{b}]")
+                no_sync_collection: Set[Collection] = kwargs.get("no_sync_collection", set())
+                object_trace(f"Syncing [{a}] = [{b}]; {no_sync_collection}")
+                if id(b) in no_sync_collection:
+                    continue
 
-                for synced_with, key in b._collection_for.items():
+
+                b_data = b.data.copy()
+                b_collection_for = b._collection_for.copy()
+                no_sync_collection.add(id(b))
+                kwargs["no_sync_collection"] = no_sync_collection
+                del b
+
+                for synced_with, key in b_collection_for.items():
                     synced_with.__setattr__(key, a)
-                a._collection_for.update(b._collection_for)
+                    a._collection_for[synced_with] = key
 
-                a.extend(b.data, **kwargs)
+                    print(synced_with, key)
 
+                a.extend(b_data, **kwargs)
+            
         else:
             # merge only if the two objects are not the same
             if existing_object.id == __object.id:

music_kraken/objects/parents.py

@@ -45,6 +45,7 @@ class InnerData:
         for key, value in kwargs.items():
             if hasattr(value, "__is_collection__"):
                 value._collection_for[self] = key
+                
             self.__setattr__(key, value)
 
     def __hash__(self):