Avoid omitting copied objects as circular dependencies

logtail/frame.py

@@ -60,23 +60,28 @@ def _parse_custom_events(record, include_extra_attributes):
 def _remove_circular_dependencies(obj, memo=None):
     if memo is None:
         memo = set()
+
     # Skip immutable types, which can't contain circular dependencies
-    if isinstance(obj, (str, int, float, bool)):
+    if isinstance(obj, (str, int, float, bool, type(None))):
         return obj
-    if id(obj) in memo:
+
+    # For mutable objects, check for circular references
+    obj_id = id(obj)
+    if obj_id in memo:
         return "<omitted circular reference>"
-    memo.add(id(obj))
+    memo.add(obj_id)
+
     if isinstance(obj, dict):
         new_dict = {}
         for key, value in obj.items():
-            new_dict[key] = _remove_circular_dependencies(value, memo)
+            new_dict[key] = _remove_circular_dependencies(value, memo.copy())
         return new_dict
     elif isinstance(obj, list):
-        return [_remove_circular_dependencies(item, memo) for item in obj]
+        return [_remove_circular_dependencies(item, memo.copy()) for item in obj]
     elif isinstance(obj, tuple):
-        return tuple(_remove_circular_dependencies(item, memo) for item in obj)
+        return tuple(_remove_circular_dependencies(item, memo.copy()) for item in obj)
     elif isinstance(obj, set):
-        return {_remove_circular_dependencies(item, memo) for item in obj}
+        return {_remove_circular_dependencies(item, memo.copy()) for item in obj}
     else:
         return obj