From 12574b542cf496639747c1908506d921ffb4b46b Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 9 Oct 2026 22:04:17 +0000
Subject: [PATCH] Only reject '-' in replace when it refers to an array (#212)

ReplaceOperation.apply rejected every path ending in '-', including
paths where '-' names an object member. RFC 6901 gives '-' a special
meaning only for arrays, so make_patch could emit a replace of an
object member '-' that apply then refused.

Move the check into the array branch. Replacing a missing '-' member
of an object now raises JsonPatchConflict, like any other missing
member, instead of InvalidJsonPatch.

Drop the expectedFailure markers from test_roundtrip and
test_replace_any_existing_location, which pass now.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFifAtR66mm468E2xYSRmw
---
 jsonpatch.py      |  8 +++++---
 property_tests.py |  6 ++----
 tests.py          | 22 ++++++++++++++++++++++
 3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/jsonpatch.py b/jsonpatch.py
index 5383aec..c8084da 100644
--- a/jsonpatch.py
+++ b/jsonpatch.py
@@ -304,10 +304,12 @@ def apply(self, obj):
         if part is None:
             return value
 
-        if part == "-":
-            raise InvalidJsonPatch("'path' with '-' can't be applied to 'replace' operation")
-
         if isinstance(subobj, MutableSequence):
+            # '-' only refers to the (nonexistent) element after the end of
+            # an array; for an object it is an ordinary member name
+            if part == "-":
+                raise InvalidJsonPatch("'path' with '-' can't be applied to 'replace' operation")
+
             if part >= len(subobj) or part < 0:
                 raise JsonPatchConflict("can't replace outside of list")
 
diff --git a/property_tests.py b/property_tests.py
index 9e92ebf..e4a24bb 100644
--- a/property_tests.py
+++ b/property_tests.py
@@ -284,9 +284,8 @@ def test_diff_of_equal_documents_is_empty(self, doc):
         self.assertEqual(list(jsonpatch.make_patch(doc, copy.deepcopy(doc))),
                          [])
 
-    @unittest.expectedFailure
     @given(doc_pairs)
-    # replace of the object member '-' is rejected
+    # replace of the object member '-' was rejected, #212
     @example(docs=({'-': 0}, {'-': 1}))
     def test_roundtrip(self, docs):
         self.check_roundtrip(*docs)
@@ -417,9 +416,8 @@ def test_move_into_own_child_fails(self, case):
             jsonpatch.apply_patch(
                 doc, [{'op': 'move', 'from': source, 'path': target}])
 
-    # '-' is rejected even where it is an object key, not an array index
-    @unittest.expectedFailure
     @given(docs_with_locations(), json_docs)
+    # '-' was rejected even where it is an object key, not an array index, #212
     @example(case=({'-': None}, ['-']), value=0)
     def test_replace_any_existing_location(self, case, value):
         doc, parts = case
diff --git a/tests.py b/tests.py
index af42fbc..f7a8287 100755
--- a/tests.py
+++ b/tests.py
@@ -95,6 +95,19 @@ def test_replace_object_key(self):
         res = jsonpatch.apply_patch(obj, [{'op': 'replace', 'path': '/baz', 'value': 'boo'}])
         self.assertTrue(res['baz'], 'boo')
 
+    def test_replace_object_key_dash(self):
+        # '-' only has a special meaning for arrays (#212)
+        obj = {'foo': {'-': 'bar', 'baz': 'qux'}}
+        res = jsonpatch.apply_patch(obj, [{'op': 'replace', 'path': '/foo/-',
+                                           'value': 'boo'}])
+        self.assertEqual(res, {'foo': {'-': 'boo', 'baz': 'qux'}})
+
+    def test_replace_array_dash(self):
+        obj = {'foo': ['bar', 'qux']}
+        with self.assertRaises(jsonpatch.InvalidJsonPatch):
+            jsonpatch.apply_patch(obj, [{'op': 'replace', 'path': '/foo/-',
+                                         'value': 'boo'}])
+
     def test_replace_whole_document(self):
         obj = {'foo': 'bar'}
         res = jsonpatch.apply_patch(obj, [{'op': 'replace', 'path': '', 'value': {'baz': 'qux'}}])
@@ -847,6 +860,11 @@ def test_issue_179(self):
             with self.subTest(old=old, new=new):
                 self.assertMakesPatch(old, new)
 
+    def test_issue_212(self):
+        """A changed object member named '-' is replaced, not rejected."""
+        self.assertMakesPatch({'-': 0}, {'-': 1})
+        self.assertMakesPatch({'a': {'-': [1]}}, {'a': {'-': [2]}})
+
     def test_move_with_numeric_object_keys(self):
         """Object keys that look like array indices are not shifted."""
         self.assertMakesPatch({'0': None, 'a': []}, {'1': [], 'a': [None]})
@@ -1308,6 +1326,10 @@ def test_replace_operation_structure(self):
             jsonpatch.ReplaceOperation({'path': '/'}).apply({})
 
         with self.assertRaises(jsonpatch.InvalidJsonPatch):
+            jsonpatch.ReplaceOperation({'path': '/top/-', 'value': 'foo'}).apply({'top': ['value']})
+
+        # for an object, '-' is an ordinary member name (#212)
+        with self.assertRaises(jsonpatch.JsonPatchConflict):
             jsonpatch.ReplaceOperation({'path': '/top/-', 'value': 'foo'}).apply({'top': {'inner': 'value'}})
 
         with self.assertRaises(jsonpatch.JsonPatchConflict):