action selection flag when patching

dictdiffer/__init__.py

@@ -275,7 +275,7 @@ 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, action_flags="arc"):
     """Patch the diff result to the destination dictionary.
 
     :param diff_result: Changes returned by ``diff``.
@@ -285,6 +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 action_flags: By default ('arc'), apply all actions: "add", "remove",
+                     "change". Setting ``actions_flag='a'`` means that
+                     pactch will apply only "add" items in the ``diff_result
+                     ``. Similarly, 'ac' only apply "add" and "change".
     """
     if not in_place:
         destination = deepcopy(destination)
@@ -325,7 +329,8 @@ def remove(node, changes):
     }
 
     for action, node, changes in diff_result:
-        patchers[action](node, changes)
+        if action[0] in action_flags:
+            patchers[action](node, changes)
 
     return destination
 

dictdiffer/version.py

@@ -1,6 +1,6 @@
-# -*- coding: utf-8 -*-
-# Do not change the format of this next line. Doing so risks breaking
-# setup.py and docs/conf.py
-"""Version information for dictdiffer package."""
-
-__version__ = '0.9.0'
+# -*- coding: utf-8 -*-
+# Do not change the format of this next line. Doing so risks breaking
+# setup.py and docs/conf.py
+"""Version information for dictdiffer package."""
+
+__version__ = '0.9.0'

docs/index.rst

@@ -76,6 +76,13 @@ Now we can apply the diff result with :func:`.patch` method:
 
     assert patched == second
 
+use `action_flags` parameter to select desired actions:
+'a' for 'add','r' for 'remove', 'c' for 'change' or any other
+combinations.
+
+.. code-block:: python
+
+    patched = patch(result, first, action_flags='a')
 
 Also we can swap the diff result with :func:`.swap` method:
 

tests/test_utils.py

@@ -8,6 +8,7 @@
 
 import unittest
 
+from dictdiffer import diff, patch
 from dictdiffer.utils import (PathLimit, WildcardDict, create_dotted_node,
                               dot_lookup, get_path, is_super_path, nested_hash)
 
@@ -144,3 +145,46 @@ def test_nested_hash(self):
         nested_hash((1, 2, 3))
         nested_hash(set([1, 2, 3]))
         nested_hash({'foo': 'bar'})
+
+    def test_limit_actions_patch(self):
+        x = {"a": True, "b": {"b1": True, "b2": False}, "c": {"c1": True}}
+        y = {"a": False, "b": {"b1": True}, "c": {"c1": False, "c2": False}}
+        z_a = {
+            "a": True,
+            "b": {"b1": True, "b2": False},
+            "c": {"c1": True, "c2": False},
+        }  # add only
+        z_r = {"a": True, "b": {"b1": True}, "c": {"c1": True}}  # remove only
+        z_c = {
+            "a": False,
+            "b": {"b1": True, "b2": False},
+            "c": {"c1": False},
+        }  # change only
+        z_ar = {
+            "a": True,
+            "b": {"b1": True},
+            "c": {"c1": True, "c2": False},
+        }  # add and remove
+        z_ac = {
+            "a": False,
+            "b": {"b1": True, "b2": False},
+            "c": {"c1": False, "c2": False},
+        }  # add and change
+        z_rc = {
+            "a": False,
+            "b": {"b1": True},
+            "c": {"c1": False}}  # remove and change
+        z_arc = y  # all actions. Default
+        test_dict = {
+            "a": z_a,
+            "r": z_r,
+            "c": z_c,
+            "ar": z_ar,
+            "ac": z_ac,
+            "rc": z_rc,
+            "arc": z_arc,
+        }
+        for k in test_dict:
+            result = diff(x, y)
+            patched = patch(result, x, action_flags=k)
+            self.assertEqual(patched, test_dict[k])