Allow Missing Keys in patch and revert

dictdiffer/__init__.py

@@ -273,7 +273,9 @@ def check(key):
     return _diff_recursive(first, second, node)
 
 
-def patch(diff_result, destination, in_place=False):
+def patch(
+    diff_result, destination, in_place=False, allow_missing_keys=False
+):
     """Patch the diff result to the destination dictionary.
 
     :param diff_result: Changes returned by ``diff``.
@@ -283,6 +285,10 @@ def patch(diff_result, destination, in_place=False):
                      Setting ``in_place=True`` means that patch will apply
                      the changes directly to and return the destination
                      structure.
+    :param allow_missing_keys: By default, trying to remove a missing
+                            key will raise a KeyError. Setting
+                            ``allow_missing_keys=True``` will silently
+                            ignore this error.
     """
     if not in_place:
         destination = deepcopy(destination)
@@ -314,7 +320,13 @@ def remove(node, changes):
             if isinstance(dest, SET_TYPES):
                 dest -= value
             else:
-                del dest[key]
+                try:
+                    del dest[key]
+                except KeyError:
+                    if allow_missing_keys:
+                        pass
+                    else:
+                        raise
 
     patchers = {
         REMOVE: remove,
@@ -368,7 +380,9 @@ def change(node, changes):
         yield swappers[action](node, change)
 
 
-def revert(diff_result, destination, in_place=False):
+def revert(
+    diff_result, destination, in_place=False, allow_missing_keys=False
+):
     """Call swap function to revert patched dictionary object.
 
     Usage example:
@@ -386,5 +400,12 @@ def revert(diff_result, destination, in_place=False):
                      is returned. Setting ``in_place=True`` means
                      that revert will apply the changes directly to
                      and return the destination structure.
+    :param allow_missing_keys: By default, trying to remove a missing
+                            key will raise a KeyError. Setting
+                            ``allow_missing_keys=True``` will silently
+                            ignore this error.
     """
-    return patch(swap(diff_result), destination, in_place)
+    return patch(
+        swap(diff_result), destination, in_place,
+        allow_missing_keys=allow_missing_keys
+    )