handle dict subclasses gracefully in PyArg_ValidateKeywordArguments

Lib/test/test_dict.py

@@ -8,10 +8,13 @@ import gc, weakref
 class DictTest(unittest.TestCase):
 
     def test_invalid_keyword_arguments(self):
-        with self.assertRaises(TypeError):
-            dict(**{1 : 2})
-        with self.assertRaises(TypeError):
-            {}.update(**{1 : 2})
+        class Custom(dict):
+            pass
+        for invalid in {1 : 2}, Custom({1 : 2}):
+            with self.assertRaises(TypeError):
+                dict(**invalid)
+            with self.assertRaises(TypeError):
+                {}.update(**invalid)
 
     def test_constructor(self):
         # calling built-in types without argument must return empty

Misc/NEWS

@@ -26,6 +26,11 @@ Library
 - Issue #10429: IMAP.starttls() stored the capabilities as bytes objects,
   rather than strings.
 
+C-API
+-----
+
+- Loosen PyArg_ValidateKeywordArguments to allow dict subclasses.
+
 
 What's New in Python 3.2 Alpha 4?
 =================================

Objects/dictobject.c

@@ -454,7 +454,7 @@ _PyDict_HasOnlyStringKeys(PyObject *dict)
 {
     Py_ssize_t pos = 0;
     PyObject *key, *value;
-    assert(PyDict_CheckExact(dict));
+    assert(PyDict_Check(dict));
     /* Shortcut */
     if (((PyDictObject *)dict)->ma_lookup == lookdict_unicode)
         return 1;

Python/getargs.c

@@ -1394,7 +1394,7 @@ _PyArg_VaParseTupleAndKeywords_SizeT(PyObject *args,
 int
 PyArg_ValidateKeywordArguments(PyObject *kwargs)
 {
-    if (!PyDict_CheckExact(kwargs)) {
+    if (!PyDict_Check(kwargs)) {
         PyErr_BadInternalCall();
         return 0;
     }