Optimize "deep" `replace` operation, fixes #36

jsonpatch.py

@@ -756,10 +756,17 @@ def _optimize(operations):
 
 
 def _optimize_using_replace(prev, cur):
-    """Optimises JSON patch by using ``replace`` operation instead of
+    """Optimises by replacing ``add``/``remove`` with ``replace`` on same path
-    ``remove`` and ``add`` against the same path."""
+
+    For nested strucures, tries to recurse replacement, see #36 """
     prev['op'] = 'replace'
     if cur['op'] == 'add':
+        # make recursive patch
+        patch = make_patch(prev['value'], cur['value'])
+        if len(patch.patch) == 1:
+            prev['path'] = prev['path'] + patch.patch[0]['path']
+            prev['value'] = patch.patch[0]['value']
+        else:
             prev['value'] = cur['value']
 
 

tests.py

@@ -366,6 +366,24 @@ class MakePatchTestCase(unittest.TestCase):
         dest = [7, 2, 1, 0, 9, 4, 3, 6, 5, 8]
         patch = jsonpatch.make_patch(src, dest)
 
+    def test_minimal_patch(self):
+        """ Test whether a minimal patch is created, see #36 """
+        src = [{"foo": 1, "bar": 2}]
+        dst = [{"foo": 2, "bar": 2}]
+        import pudb
+        #pudb.set_trace()
+        patch = jsonpatch.make_patch(src, dst)
+
+        exp = [
+            {
+                "path": "/0/foo",
+                "value": 2,
+                "op": "replace"
+            }
+        ]
+
+        self.assertEqual(patch.patch, exp)
+
 
 class InvalidInputTests(unittest.TestCase):