Remove extraneous 'value' field for op:remove (#76)

RFC 6902 section 4.2 [0] does not define a 'value' field for
the 'remove' operation.  The commit "Merge _op_base classes
into PatchOperation classes" [1] introduced a 'value' field
in _item_removed() in the DiffBuilder class.  This patch
removes the 'value' field from the 'remove' operation, adds
a new test, and revises some other tests.

[0] https://tools.ietf.org/html/rfc6902#section-4.2
[1] 03aa14e

Author: ostackbrian

jsonpatch.py

@@ -730,7 +730,6 @@ def _item_removed(self, path, key, item):
         new_op = RemoveOperation({
             'op': 'remove',
             'path': _path_join(path, key),
-            'value': item,
         })
         index = self.take_index(item, _ST_ADD)
         new_index = self.insert(new_op)

tests.py

@@ -368,6 +368,17 @@ def test_issue40(self):
         dest = [7, 2, 1, 0, 9, 4, 3, 6, 5, 8]
         patch = jsonpatch.make_patch(src, dest)
 
+    def test_issue76(self):
+        """ Make sure op:remove does not include a 'value' field """
+
+        src = { "name": "fred", "friend": "barney", "spouse": "wilma" }
+        dst = { "name": "fred", "spouse": "wilma" }
+        expected = [{"path": "/friend", "op": "remove"}]
+        patch = jsonpatch.make_patch(src, dst)
+        self.assertEqual(patch.patch, expected)
+        res = jsonpatch.apply_patch(src, patch)
+        self.assertEqual(res, dst)
+
     def test_json_patch(self):
         old = {
             'queue': {'teams_out': [{'id': 3, 'reason': 'If tied'}, {'id': 5, 'reason': 'If tied'}]},
@@ -424,7 +435,7 @@ def test_use_replace_instead_of_remove_add_nested(self):
         dst = {'foo': [{'bar': 1}, {'bar': 2, 'baz': 3}]}
         patch = list(jsonpatch.make_patch(src, dst))
 
-        exp = [{'op': 'remove', 'value': 2, 'path': '/foo/0/baz'}]
+        exp = [{'op': 'remove', 'path': '/foo/0/baz'}]
         self.assertEqual(patch, exp)
 
         res = jsonpatch.apply_patch(src, patch)
@@ -481,11 +492,14 @@ def test_success_if_correct_expected_patch_appied(self):
         src = [{"a": 1, "b": 2}]
         dst = [{"b": 2, "c": 2}]
         exp = [
-            {'path': '/0/a', 'op': 'remove', 'value': 1},
+            {'path': '/0/a', 'op': 'remove'},
             {'path': '/0/c', 'op': 'add', 'value': 2}
         ]
         patch = jsonpatch.make_patch(src, dst)
         self.assertEqual(patch.patch, exp)
+        # verify that this patch does what we expect
+        res = jsonpatch.apply_patch(src, patch)
+        self.assertEqual(res, dst)
 
     def test_minimal_patch(self):
         """ Test whether a minimal patch is created, see #36 """