_json: add native make_encoder (c_make_encoder)

json.encoder fell back to the pure-Python _make_iterencode because _json had no make_encoder, making json.dumps ~25x slower than CPython. Implement the C encoder semantics natively: str/None/bool/int/float/list/tuple/dict ordering, key coercion and skipkeys, sort_keys via the VM's fallible sort (comparison errors propagate instead of panicking), circular reference detection, indent handling, allow_nan, default() fallback with recursion guard, and CPython's add_note annotations. Removes the now-passing expectedFailure markers in test_json. Assisted-by: Claude Code:claude-fable-5-1
moreal · Sep 7, 2026 · Sep 7, 2026 · Sep 7, 2026 · Sep 7, 2026 · Sep 7, 2026
commit d45290533553ee4bfdc4420e10449604ce7b8e1a
diff --git a/Lib/test/test_json/__init__.py b/Lib/test/test_json/__init__.py
@@ -41,7 +41,6 @@ def test_pyjson(self):
                          'json.encoder')
 
 class TestCTest(CTest):
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_cjson(self):
         self.assertEqual(self.json.scanner.make_scanner.__module__, '_json')
         self.assertEqual(self.json.decoder.scanstring.__module__, '_json')

diff --git a/Lib/test/test_json/test_speedups.py b/Lib/test/test_json/test_speedups.py
@@ -41,7 +41,6 @@ def test_make_encoder(self):
             b"\xCD\x7D\x3D\x4E\x12\x4C\xF9\x79\xD7\x52\xBA\x82\xF2\x27\x4A\x7D\xA0\xCA\x75",
             None)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: 'NoneType' object is not callable
     def test_bad_str_encoder(self):
         # Issue #31505: There shouldn't be an assertion failure in case
         # c_make_encoder() receives a bad encoder() argument.
@@ -63,7 +62,6 @@ def bad_encoder2(*args):
         with self.assertRaises(ZeroDivisionError):
             enc('spam', 4)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_bad_markers_argument_to_encoder(self):
         # https://bugs.python.org/issue45269
         with self.assertRaisesRegex(
@@ -73,7 +71,6 @@ def test_bad_markers_argument_to_encoder(self):
             self.json.encoder.c_make_encoder(1, None, None, None, ': ', ', ',
                                              False, False, False)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ZeroDivisionError not raised by test
     def test_bad_bool_args(self):
         def test(name):
             self.json.encoder.JSONEncoder(**{name: BadBool()}).encode({'a': 1})
@@ -119,7 +116,6 @@ def test_current_indent_level(self):
         self.assertRaises(TypeError, enc, ['spam', {'ham': 'eggs'}], 3.0)
         self.assertRaises(TypeError, enc, ['spam', {'ham': 'eggs'}])
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: 'NoneType' object is not callable
     def test_mutate_dict_items_during_encode(self):
         # gh-142831: Clearing the items list via a re-entrant key encoder
         # must not cause a use-after-free.  BadDict.items() returns a
@@ -153,7 +149,6 @@ def encode_str(obj):
         encoder(BadDict(real=1), 0)
         self.assertTrue(cleared)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: 'NoneType' object is not callable
     def test_mutate_list_during_encode(self):
         # gh-142831: Clearing a list mid-iteration via the default
         # callback must not cause a use-after-free.