fix sending tuples to custom generator objects with yield from (closes #21209)

Debugged by Victor.

Lib/test/test_pep380.py

@@ -993,6 +993,25 @@ class TestPEP380Operation(unittest.TestCase):
             del inner_gen
             gc_collect()
 
+    def test_send_tuple_with_custom_generator(self):
+        # See issue #21209.
+        class MyGen:
+            def __iter__(self):
+                return self
+            def __next__(self):
+                return 42
+            def send(self, what):
+                nonlocal v
+                v = what
+                return None
+        def outer():
+            v = yield from MyGen()
+        g = outer()
+        next(g)
+        v = None
+        g.send((1, 2, 3, 4))
+        self.assertEqual(v, (1, 2, 3, 4))
+
 
 def test_main():
     from test import support

Misc/NEWS

@@ -10,6 +10,9 @@ Release date: TBA
 Core and Builtins
 -----------------
 
+- Issue #21209: Fix sending tuples to custom generator objects with the yield
+  from syntax.
+
 - Issue #21134: Fix segfault when str is called on an uninitialized
   UnicodeEncodeError, UnicodeDecodeError, or UnicodeTranslateError object.
 

Python/ceval.c

@@ -1902,7 +1902,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
                 if (v == Py_None)
                     retval = Py_TYPE(reciever)->tp_iternext(reciever);
                 else
-                    retval = _PyObject_CallMethodId(reciever, &PyId_send, "O", v);
+                    retval = _PyObject_CallMethodIdObjArgs(reciever, &PyId_send, v, NULL);
             }
             Py_DECREF(v);
             if (retval == NULL) {