Add support for diff_class in DiffElement

Author: dgarros

dsync/__init__.py

@@ -852,7 +852,12 @@ def diff_object_pair(self, src_obj: Optional[DSyncModel], dst_obj: Optional[DSyn
             return None
 
         diff_element = DiffElement(
-            obj_type=model, name=shortname, keys=keys, source_name=self.src_dsync.name, dest_name=self.dst_dsync.name,
+            obj_type=model,
+            name=shortname,
+            keys=keys,
+            source_name=self.src_dsync.name,
+            dest_name=self.dst_dsync.name,
+            diff_class=self.diff_class,
         )
 
         if src_obj:

dsync/diff.py

@@ -16,7 +16,7 @@
 """
 
 from functools import total_ordering
-from typing import Any, Iterator, Iterable, Mapping, Optional, Text
+from typing import Any, Iterator, Iterable, Mapping, Optional, Text, Type
 
 from .exceptions import ObjectAlreadyExists
 from .utils import intersection, OrderedDefaultDict
@@ -126,7 +126,13 @@ class DiffElement:  # pylint: disable=too-many-instance-attributes
     """DiffElement object, designed to represent a single item/object that may or may not have any diffs."""
 
     def __init__(
-        self, obj_type: Text, name: Text, keys: Mapping, source_name: Text = "source", dest_name: Text = "dest"
+        self,
+        obj_type: Text,
+        name: Text,
+        keys: Mapping,
+        source_name: Text = "source",
+        dest_name: Text = "dest",
+        diff_class: Type[Diff] = Diff,
     ):  # pylint: disable=too-many-arguments
         """Instantiate a DiffElement.
 
@@ -152,7 +158,7 @@ def __init__(
         # Note: *_attrs == None if no target object exists; it'll be an empty dict if it exists but has no _attributes
         self.source_attrs: Optional[Mapping] = None
         self.dest_attrs: Optional[Mapping] = None
-        self.child_diff = Diff()
+        self.child_diff = diff_class()
 
     def __lt__(self, other):
         """Logical ordering of DiffElements.

tests/unit/test_dsync.py

@@ -271,7 +271,12 @@ def check_diff_symmetry(diff1, diff2):
 
 def test_dsync_diff_from_with_custom_diff_class(backend_a, backend_b):
     diff_ba = backend_a.diff_from(backend_b, diff_class=TrackedDiff)
+    diff_children = diff_ba.get_children()
+
     assert isinstance(diff_ba, TrackedDiff)
+    for child in diff_children:
+        if child.child_diff:
+            assert isinstance(child.child_diff, TrackedDiff)
     assert diff_ba.is_complete is True