Preserve dictionary key casing in case-insensitive diff paths

CHANGELOG.md

@@ -1,6 +1,7 @@
 # DeepDiff Change log
 
 - Unreleased
+    - Preserve original string key casing in reported paths when `ignore_string_case=True`, so path exclusions can use the input keys (#515).
     - Fixed missing type changes between equal-comparing items inside ordered iterables, e.g. `DeepDiff([2], [2.0])` now reports the `int` → `float` change like `DeepDiff(2, 2.0)` and `DeepDiff({'a': 2}, {'a': 2.0})` already do (issue #605).
 
 - v9-1-0

deepdiff/diff.py

@@ -813,13 +813,15 @@ def _diff_dict(
                 continue
             parents_ids_added = add_to_frozen_set(parents_ids, item_id)
 
+            # Case normalization is for matching, not for paths into the input objects.
+            preserve_case = self.ignore_string_case and isinstance(key1, str) and isinstance(key2, str)
             # Go one level deeper
             next_level = level.branch_deeper(
                 t1[key1],
                 t2[key2],
                 child_relationship_class=rel_class,
-                child_relationship_param=key,
-                child_relationship_param2=key,
+                child_relationship_param=key1 if preserve_case else key,
+                child_relationship_param2=key2 if preserve_case else key,
                 )
             self._diff(next_level, parents_ids_added, local_tree=local_tree)
 

tests/test_diff_text.py

@@ -369,6 +369,36 @@ def test_string_dict_key_ignore_case(self):
         result = {}
         assert result == ddiff
 
+    def test_ignore_case_preserves_original_dictionary_paths(self):
+        t1 = {'User': {'AboutMe': 1}}
+        t2 = {'user': {'aboutme': 2}}
+        diff = DeepDiff(t1, t2, ignore_string_case=True)
+        assert diff == {'values_changed': {
+            "root['User']['AboutMe']": {'old_value': 1, 'new_value': 2}
+        }}
+        tree = DeepDiff(t1, t2, ignore_string_case=True, view='tree')
+        change = next(iter(tree['values_changed']))
+        assert change.path() == "root['User']['AboutMe']"
+        assert change.path(use_t2=True) == "root['user']['aboutme']"
+
+    @pytest.mark.parametrize('path_option', ['exclude_paths', 'exclude_regex_paths'])
+    def test_ignore_case_excludes_original_dictionary_path(self, path_option):
+        t1 = {'User': {'AboutMe': 1}}
+        t2 = {'User': {'AboutMe': 2}}
+        path = "root['User']['AboutMe']"
+        if path_option == 'exclude_regex_paths':
+            path = r"root\['User'\]\['AboutMe'\]$"
+        assert not DeepDiff(t1, t2, ignore_string_case=True, **{path_option: [path]})
+
+    def test_ignore_case_preserves_paths_for_nested_additions_and_removals(self):
+        t1 = {'User': {'Keep': 1, 'Removed': 2}}
+        t2 = {'user': {'keep': 1, 'Added': 3}}
+        diff = DeepDiff(t1, t2, ignore_string_case=True, threshold_to_diff_deeper=0)
+        assert diff == {
+            'dictionary_item_added': ["root['User']['Added']"],
+            'dictionary_item_removed': ["root['User']['Removed']"],
+        }
+
     def test_string_list_ignore_case(self):
         t1 = ['AboutMe', 'ALIAS']
         t2 = ['aboutme', 'alias']