gh-124748: Fix handling kwargs in WeakKeyDictionary.update() (#124783)

Lib/test/test_weakref.py

@@ -1815,6 +1815,11 @@ def test_weak_valued_union_operators(self):
     def test_weak_keyed_dict_update(self):
         self.check_update(weakref.WeakKeyDictionary,
                           {C(): 1, C(): 2, C(): 3})
+        d = weakref.WeakKeyDictionary()
+        msg = ("Keyword arguments are not supported: "
+               "cannot create weak reference to 'str' object")
+        with self.assertRaisesRegex(TypeError, msg):
+            d.update(k='v')
 
     def test_weak_keyed_delitem(self):
         d = weakref.WeakKeyDictionary()

Lib/weakref.py

@@ -408,14 +408,16 @@ def setdefault(self, key, default=None):
         return self.data.setdefault(ref(key, self._remove),default)
 
     def update(self, dict=None, /, **kwargs):
+        if kwargs:
+            msg = ("Keyword arguments are not supported: "
+                   "cannot create weak reference to 'str' object")
+            raise TypeError(msg)
         d = self.data
         if dict is not None:
             if not hasattr(dict, "items"):
                 dict = type({})(dict)
             for key, value in dict.items():
                 d[ref(key, self._remove)] = value
-        if len(kwargs):
-            self.update(kwargs)
 
     def __ior__(self, other):
         self.update(other)

Misc/NEWS.d/next/Library/2024-09-30-15-31-59.gh-issue-124748.KYzYFp.rst

@@ -0,0 +1,2 @@
+Improve :exc:`TypeError` error message when :meth:`!weakref.WeakKeyDictionary.update`
+is used with keyword-only parameters.