Adding support for applying deltas to NamedTuple

Author: paulsc

deepdiff/delta.py

@@ -330,11 +330,21 @@ def _set_new_value(self, parent, parent_to_obj_elem, parent_to_obj_action,
         Set the element value on an object and if necessary convert the object to the proper mutable type
         """
         if isinstance(obj, tuple):
-            # convert this object back to a tuple later
-            obj = self._coerce_obj(
-                parent, obj, path, parent_to_obj_elem,
-                parent_to_obj_action, elements,
-                to_type=list, from_type=tuple)
+            # Check if it's a NamedTuple and use _replace() to generate a new copy with the change
+            if hasattr(obj, '_fields') and hasattr(obj, '_replace'):
+                if action == GETATTR:
+                    obj = obj._replace(**{elem: new_value})
+                    if parent:
+                        self._simple_set_elem_value(obj=parent, path_for_err_reporting=path,
+                                                    elem=parent_to_obj_elem, value=obj,
+                                                    action=parent_to_obj_action)
+                return
+            else:
+                # Regular tuple - convert this object back to a tuple later
+                obj = self._coerce_obj(
+                    parent, obj, path, parent_to_obj_elem,
+                    parent_to_obj_action, elements,
+                    to_type=list, from_type=tuple)
         if elem != 0 and self.force and isinstance(obj, list) and len(obj) == 0:
             # it must have been a dictionary    
             obj = {}

tests/test_delta.py

@@ -1,5 +1,6 @@
 import copy
 import datetime
+from typing import NamedTuple
 import pytest
 import os
 import io
@@ -624,6 +625,17 @@ def compare_func(item1, item2, level=None):
         assert flat_rows_list == preserved_flat_dict_list
         assert flat_rows_list == flat_rows_list_again
 
+    def test_namedtuple_add_delta(self):
+        class Point(NamedTuple):
+           x: int
+           y: int
+
+        p1 = Point(1, 1)
+        p2 = Point(1, 2)
+        diff = DeepDiff(p1, p2)
+        delta = Delta(diff)
+        assert p2 == p1 + delta
+
 
 picklalbe_obj_without_item = PicklableClass(11)
 del picklalbe_obj_without_item.item