restrict keyword placeholders

Author: dg-pb

Lib/functools.py

@@ -342,6 +342,10 @@ class partial:
     def __new__(cls, func, /, *args, **keywords):
         if not callable(func):
             raise TypeError("the first argument must be callable")
+        if keywords:
+            for v in keywords.values():
+                if v is Placeholder:
+                    raise TypeError("keyword Placeholders are not allowed")
         if isinstance(func, partial):
             pto_phcount = func._phcount
             tot_args = func.args

Lib/test/test_functools.py

@@ -254,6 +254,12 @@ def test_placeholders_optimization(self):
         self.assertEqual(p2.args, (PH, 0))
         self.assertEqual(p2(1), ((1, 0), {}))
 
+    def test_placeholders_kw_restriction(self):
+        PH = self.module.Placeholder
+        exc_string = 'keyword Placeholders are not allowed'
+        with self.assertRaisesRegex(TypeError, exc_string):
+            self.partial(capture, a=PH)
+
     def test_construct_placeholder_singleton(self):
         PH = self.module.Placeholder
         tp = type(PH)

Modules/_functoolsmodule.c

@@ -290,29 +290,31 @@ partial_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 
     /* process keywords */
     if (pto_kw == NULL || PyDict_GET_SIZE(pto_kw) == 0) {
-        if (kw == NULL) {
-            pto->kw = PyDict_New();
-        }
-        else if (Py_REFCNT(kw) == 1) {
-            pto->kw = Py_NewRef(kw);
-        }
-        else {
-            pto->kw = PyDict_Copy(kw);
-        }
+        pto->kw = PyDict_New();
     }
     else {
         pto->kw = PyDict_Copy(pto_kw);
-        if (kw != NULL && pto->kw != NULL) {
-            if (PyDict_Merge(pto->kw, kw, 1) != 0) {
+        if (pto->kw == NULL) {
+            Py_DECREF(pto);
+            return NULL;
+        }
+    }
+    if (kw != NULL && pto->kw != NULL) {
+        PyObject *key, *val;
+        Py_ssize_t pos = 0;
+        while (PyDict_Next(kw, &pos, &key, &val)) {
+            if (val == phold) {
+                Py_DECREF(pto);
+                PyErr_SetString(PyExc_TypeError,
+                                "keyword Placeholders are not allowed");
+                return NULL;
+            }
+            if (PyDict_SetItem(pto->kw, key, val)) {
                 Py_DECREF(pto);
                 return NULL;
             }
         }
     }
-    if (pto->kw == NULL) {
-        Py_DECREF(pto);
-        return NULL;
-    }
 
     partial_setvectorcall(pto);
     return (PyObject *)pto;