subtract delta

Author: seperman

CHANGELOG.md

@@ -1,5 +1,11 @@
 # DeepDiff Change log
 
+- v6-7-0
+    - Delta can be subtracted from other objects now.
+    - verify_symmetry is deprecated. Use bidirectional instead.
+    - always_include_values flag in Delta can be enabled to include values in the delta for every change.
+    - Fix for Delta.__add__ breaks with esoteric dict keys.
+    - You can load a delta from the list of flat dictionaries.
 - v6-6-1
     - Fix for [DeepDiff raises decimal exception when using significant digits](https://github.com/seperman/deepdiff/issues/426)
     - Introducing group_by_sort_key

README.md

@@ -23,30 +23,21 @@ Tested on Python 3.7+ and PyPy3.
 
 Please check the [ChangeLog](CHANGELOG.md) file for the detailed information.
 
+DeepDiff v6-7-0
+
+- Delta can be subtracted from other objects now.
+- verify_symmetry is deprecated. Use bidirectional instead.
+- always_include_values flag in Delta can be enabled to include values in the delta for every change.
+- Fix for Delta.__add__ breaks with esoteric dict keys.
+- You can load a delta from the list of flat dictionaries.
+
 DeepDiff 6-6-1
+
 - Fix for [DeepDiff raises decimal exception when using significant digits](https://github.com/seperman/deepdiff/issues/426)
 - Introducing group_by_sort_key
 - Adding group_by 2D. For example `group_by=['last_name', 'zip_code']`
 
 
-DeepDiff 6-6-0
-
-- [Serialize To Flat Dicts](https://zepworks.com/deepdiff/current/serialization.html#delta-to-flat-dicts-label)
-- [NumPy 2.0 compatibility](https://github.com/seperman/deepdiff/pull/422) by [William Jamieson](https://github.com/WilliamJamieson)
-
-DeepDiff 6-5-0
-
-- [parse_path](https://zepworks.com/deepdiff/current/faq.html#q-how-do-i-parse-deepdiff-result-paths)
-
-DeepDiff 6-4-1
-
-- [Add Ignore List Order Option to DeepHash](https://github.com/seperman/deepdiff/pull/403) by 
-[Bobby Morck](https://github.com/bmorck)
-- [pyyaml to 6.0.1 to fix cython build problems](https://github.com/seperman/deepdiff/pull/406) by [Robert Bo Davis](https://github.com/robert-bo-davis)
-- [Precompiled regex simple diff](https://github.com/seperman/deepdiff/pull/413) by [cohml](https://github.com/cohml)
-- New flag: `zip_ordered_iterables` for forcing iterable items to be compared one by one. 
-
-
 ## Installation
 
 ### Install from PyPi:

deepdiff/delta.py

@@ -23,8 +23,8 @@
 VERIFICATION_MSG = 'Expected the old value for {} to be {} but it is {}. Error found on: {}'
 ELEM_NOT_FOUND_TO_ADD_MSG = 'Key or index of {} is not found for {} for setting operation.'
 TYPE_CHANGE_FAIL_MSG = 'Unable to do the type change for {} from to type {} due to {}'
-VERIFY_SYMMETRY_MSG = ('while checking the symmetry of the delta. You have applied the delta to an object that has '
-                       'different values than the original object the delta was made from')
+VERIFY_BIDIRECTIONAL_MSG = ('You have applied the delta to an object that has '
+                            'different values than the original object the delta was made from.')
 FAIL_TO_REMOVE_ITEM_IGNORE_ORDER_MSG = 'Failed to remove index[{}] on {}. It was expected to be {} but got {}'
 DELTA_NUMPY_OPERATOR_OVERRIDE_MSG = (
     'A numpy ndarray is most likely being added to a delta. '
@@ -78,7 +78,9 @@ def __init__(
         raise_errors=False,
         safe_to_import=None,
         serializer=pickle_dump,
-        verify_symmetry=False,
+        verify_symmetry=None,
+        bidirectional=False,
+        always_include_values=False,
         force=False,
     ):
         if hasattr(deserializer, '__code__') and 'safe_to_import' in set(deserializer.__code__.co_varnames):
@@ -89,9 +91,21 @@ def _deserializer(obj, safe_to_import=None):
 
         self._reversed_diff = None
 
+        if verify_symmetry is not None:
+            logger.warning(
+                "DeepDiff Deprecation: use bidirectional instead of verify_symmetry parameter."
+            )
+            bidirectional = verify_symmetry
+
+        self.bidirectional = bidirectional
+        if bidirectional:
+            self.always_include_values = True  # We need to include the values in bidirectional deltas
+        else:
+            self.always_include_values = always_include_values
+
         if diff is not None:
             if isinstance(diff, DeepDiff):
-                self.diff = diff._to_delta_dict(directed=not verify_symmetry)
+                self.diff = diff._to_delta_dict(directed=not bidirectional, always_include_values=self.always_include_values)
             elif isinstance(diff, Mapping):
                 self.diff = diff
             elif isinstance(diff, strings):
@@ -112,7 +126,6 @@ def _deserializer(obj, safe_to_import=None):
             raise ValueError(DELTA_AT_LEAST_ONE_ARG_NEEDED)
 
         self.mutate = mutate
-        self.verify_symmetry = verify_symmetry
         self.raise_errors = raise_errors
         self.log_errors = log_errors
         self._numpy_paths = self.diff.pop('_numpy_paths', False)
@@ -162,16 +175,28 @@ def __add__(self, other):
 
     __radd__ = __add__
 
+    def __rsub__(self, other):
+        if self._reversed_diff is None:
+            self._reversed_diff = self._get_reverse_diff()
+        self.diff, self._reversed_diff = self._reversed_diff, self.diff
+        result = self.__add__(other)
+        self.diff, self._reversed_diff = self._reversed_diff, self.diff
+        return result
+
     def _raise_or_log(self, msg, level='error'):
         if self.log_errors:
             getattr(logger, level)(msg)
         if self.raise_errors:
             raise DeltaError(msg)
 
     def _do_verify_changes(self, path, expected_old_value, current_old_value):
-        if self.verify_symmetry and expected_old_value != current_old_value:
+        if self.bidirectional and expected_old_value != current_old_value:
+            if isinstance(path, str):
+                path_str = path
+            else:
+                path_str = stringify_path(path, root_element=('', GETATTR))
             self._raise_or_log(VERIFICATION_MSG.format(
-                path, expected_old_value, current_old_value, VERIFY_SYMMETRY_MSG))
+                path_str, expected_old_value, current_old_value, VERIFY_BIDIRECTIONAL_MSG))
 
     def _get_elem_and_compare_to_old_value(self, obj, path_for_err_reporting, expected_old_value, elem=None, action=None, forced_old_value=None):
         try:
@@ -192,7 +217,7 @@ def _get_elem_and_compare_to_old_value(self, obj, path_for_err_reporting, expect
             current_old_value = not_found
             if isinstance(path_for_err_reporting, (list, tuple)):
                 path_for_err_reporting = '.'.join([i[0] for i in path_for_err_reporting])
-            if self.verify_symmetry:
+            if self.bidirectional:
                 self._raise_or_log(VERIFICATION_MSG.format(
                     path_for_err_reporting,
                     expected_old_value, current_old_value, e))
@@ -357,7 +382,9 @@ def _do_type_changes(self):
 
     def _do_post_process(self):
         if self.post_process_paths_to_convert:
-            self._do_values_or_type_changed(self.post_process_paths_to_convert, is_type_change=True)
+            # Example: We had converted some object to be mutable and now we are converting them back to be immutable.
+            # We don't need to check the change because it is not really a change that was part of the original diff.
+            self._do_values_or_type_changed(self.post_process_paths_to_convert, is_type_change=True, verify_changes=False)
 
     def _do_pre_process(self):
         if self._numpy_paths and ('iterable_item_added' in self.diff or 'iterable_item_removed' in self.diff):
@@ -394,7 +421,7 @@ def _get_elements_and_details(self, path):
                 return None
             return elements, parent, parent_to_obj_elem, parent_to_obj_action, obj, elem, action
 
-    def _do_values_or_type_changed(self, changes, is_type_change=False):
+    def _do_values_or_type_changed(self, changes, is_type_change=False, verify_changes=True):
         for path, value in changes.items():
             elem_and_details = self._get_elements_and_details(path)
             if elem_and_details:
@@ -409,7 +436,7 @@ def _do_values_or_type_changed(self, changes, is_type_change=False):
                 continue  # pragma: no cover. I have not been able to write a test for this case. But we should still check for it.
             # With type change if we could have originally converted the type from old_value
             # to new_value just by applying the class of the new_value, then we might not include the new_value
-            # in the delta dictionary.
+            # in the delta dictionary. That is defined in Model.DeltaResult._from_tree_type_changes
             if is_type_change and 'new_value' not in value:
                 try:
                     new_type = value['new_type']
@@ -427,7 +454,8 @@ def _do_values_or_type_changed(self, changes, is_type_change=False):
             self._set_new_value(parent, parent_to_obj_elem, parent_to_obj_action,
                                 obj, elements, path, elem, action, new_value)
 
-            self._do_verify_changes(path, expected_old_value, current_old_value)
+            if verify_changes:
+                self._do_verify_changes(path, expected_old_value, current_old_value)
 
     def _do_item_removed(self, items):
         """
@@ -580,8 +608,50 @@ def _do_ignore_order(self):
             self._simple_set_elem_value(obj=parent, path_for_err_reporting=path, elem=parent_to_obj_elem,
                                         value=new_obj, action=parent_to_obj_action)
 
-    def _reverse_diff(self):
-        pass
+    def _get_reverse_diff(self):
+        if not self.bidirectional:
+            raise ValueError('Please recreate the delta with bidirectional=True')
+
+        SIMPLE_ACTION_TO_REVERSE = {
+            'iterable_item_added': 'iterable_item_removed',
+            'iterable_items_added_at_indexes': 'iterable_items_removed_at_indexes',
+            'attribute_added': 'attribute_removed',
+            'set_item_added': 'set_item_removed',
+            'dictionary_item_added': 'dictionary_item_removed',
+        }
+        # Adding the reverse of the dictionary
+        for key in list(SIMPLE_ACTION_TO_REVERSE.keys()):
+            SIMPLE_ACTION_TO_REVERSE[SIMPLE_ACTION_TO_REVERSE[key]] = key
+
+        r_diff = {}
+        for action, info in self.diff.items():
+            reverse_action = SIMPLE_ACTION_TO_REVERSE.get(action)
+            if reverse_action:
+                r_diff[reverse_action] = info
+            elif action == 'values_changed':
+                r_diff[action] = {}
+                for path, path_info in info.items():
+                    r_diff[action][path] = {
+                        'new_value': path_info['old_value'], 'old_value': path_info['new_value']
+                    } 
+            elif action == 'type_changes':
+                r_diff[action] = {}
+                for path, path_info in info.items():
+                    r_diff[action][path] = {
+                        'old_type': path_info['new_type'], 'new_type': path_info['old_type'],
+                    }
+                    if 'new_value' in path_info:
+                        r_diff[action][path]['old_value'] = path_info['new_value']
+                    if 'old_value' in path_info:
+                        r_diff[action][path]['new_value'] = path_info['old_value']
+            elif action == 'iterable_item_moved':
+                r_diff[action] = {}
+                for path, path_info in info.items():
+                    old_path = path_info['new_path']
+                    r_diff[action][old_path] = {
+                        'new_path': path, 'value': path_info['value'],
+                    }
+        return r_diff
 
     def dump(self, file):
         """
@@ -735,6 +805,7 @@ def to_flat_dicts(self, include_action_in_path=False, report_type_changes=True):
         Here are the list of actions that the flat dictionary can return.
             iterable_item_added
             iterable_item_removed
+            iterable_item_moved
             values_changed
             type_changes
             set_item_added
@@ -758,15 +829,18 @@ def to_flat_dicts(self, include_action_in_path=False, report_type_changes=True):
                 ('old_type', 'old_type', None),
                 ('new_path', 'new_path', _parse_path),
             ]
-            action_mapping = {}
         else:
+            if not self.always_include_values:
+                raise ValueError(
+                    "When converting to flat dictionaries, if report_type_changes=False and there are type changes, "
+                    "you must set the always_include_values=True at the delta object creation. Otherwise there is nothing to include."
+                )
             keys_and_funcs = [
                 ('value', 'value', None),
                 ('new_value', 'value', None),
                 ('old_value', 'old_value', None),
                 ('new_path', 'new_path', _parse_path),
             ]
-            action_mapping = {'type_changes': 'values_changed'}
 
         FLATTENING_NEW_ACTION_MAP = {
             'iterable_items_added_at_indexes': 'iterable_item_added',
@@ -819,9 +893,20 @@ def to_flat_dicts(self, include_action_in_path=False, report_type_changes=True):
                     result.append(
                         {'path': path, 'value': value, 'action': action}
                     )
+            elif action == 'type_changes':
+                if not report_type_changes:
+                    action = 'values_changed'
+
+                for row in self._get_flat_row(
+                    action=action,
+                    info=info,
+                    _parse_path=_parse_path,
+                    keys_and_funcs=keys_and_funcs,
+                ):
+                    result.append(row)
             else:
                 for row in self._get_flat_row(
-                    action=action_mapping.get(action, action),
+                    action=action,
                     info=info,
                     _parse_path=_parse_path,
                     keys_and_funcs=keys_and_funcs,

deepdiff/diff.py

@@ -493,10 +493,9 @@ def _skip_this(self, level):
         elif self.include_obj_callback_strict and level_path != 'root':
             skip = True
             if (self.include_obj_callback_strict(level.t1, level_path) and
-                self.include_obj_callback_strict(level.t2, level_path)):
+                    self.include_obj_callback_strict(level.t2, level_path)):
                 skip = False
 
-
         return skip
 
     def _get_clean_to_keys_mapping(self, keys, level):

deepdiff/model.py

@@ -279,8 +279,9 @@ def _from_tree_custom_results(self, tree):
 class DeltaResult(TextResult):
     ADD_QUOTES_TO_STRINGS = False
 
-    def __init__(self, tree_results=None, ignore_order=None):
+    def __init__(self, tree_results=None, ignore_order=None, always_include_values=False):
         self.ignore_order = ignore_order
+        self.always_include_values = always_include_values
 
         self.update({
             "type_changes": dict_(),
@@ -375,7 +376,7 @@ def _from_tree_type_changes(self, tree):
                 })
                 self['type_changes'][change.path(
                     force=FORCE_DEFAULT)] = remap_dict
-                if include_values:
+                if include_values or self.always_include_values:
                     remap_dict.update(old_value=change.t1, new_value=change.t2)
 
     def _from_tree_value_changed(self, tree):

deepdiff/serialization.py

@@ -215,7 +215,7 @@ def to_dict(self, view_override=None):
         view = view_override if view_override else self.view
         return dict(self._get_view_results(view))
 
-    def _to_delta_dict(self, directed=True, report_repetition_required=True):
+    def _to_delta_dict(self, directed=True, report_repetition_required=True, always_include_values=False):
         """
         Dump to a dictionary suitable for delta usage.
         Unlike to_dict, this is not dependent on the original view that the user chose to create the diff.
@@ -241,7 +241,7 @@ def _to_delta_dict(self, directed=True, report_repetition_required=True):
         if self.group_by is not None:
             raise ValueError(DELTA_ERROR_WHEN_GROUP_BY)
 
-        result = DeltaResult(tree_results=self.tree, ignore_order=self.ignore_order)
+        result = DeltaResult(tree_results=self.tree, ignore_order=self.ignore_order, always_include_values=always_include_values)
         result.remove_empty_keys()
         if report_repetition_required and self.ignore_order and not self.report_repetition:
             raise ValueError(DELTA_IGNORE_ORDER_NEEDS_REPETITION_REPORT)

docs/changelog.rst

@@ -5,6 +5,14 @@ Changelog
 
 DeepDiff Changelog
 
+-  v6-7-0
+
+   -  Delta can be subtracted from other objects now.
+   -  verify_symmetry is deprecated. Use bidirectional instead.
+   -  always_include_values flag in Delta can be enabled to include
+      values in the delta for every change.
+   -  Fix for Delta.\__add\_\_ breaks with esoteric dict keys.
+
 -  v6-6-1
 
     -  Fix for `DeepDiff raises decimal exception when using significant