gh-115015: Argument Clinic: fix generated code for METH_METHOD methods without params (#115016)

Author: erlend-aasland

Lib/test/clinic.test.c

@@ -4625,7 +4625,7 @@ Test_cls_no_params_impl(TestObj *self, PyTypeObject *cls);
 static PyObject *
 Test_cls_no_params(TestObj *self, PyTypeObject *cls, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
-    if (nargs) {
+    if (nargs || (kwnames && PyTuple_GET_SIZE(kwnames))) {
         PyErr_SetString(PyExc_TypeError, "cls_no_params() takes no arguments");
         return NULL;
     }
@@ -4634,7 +4634,7 @@ Test_cls_no_params(TestObj *self, PyTypeObject *cls, PyObject *const *args, Py_s
 
 static PyObject *
 Test_cls_no_params_impl(TestObj *self, PyTypeObject *cls)
-/*[clinic end generated code: output=cc8845f22cff3dcb input=e7e2e4e344e96a11]*/
+/*[clinic end generated code: output=4d68b4652c144af3 input=e7e2e4e344e96a11]*/
 
 
 /*[clinic input]

Lib/test/test_clinic.py

@@ -3288,6 +3288,26 @@ def test_cloned_func_with_converter_exception_message(self):
                 func = getattr(ac_tester, name)
                 self.assertEqual(func(), name)
 
+    def test_meth_method_no_params(self):
+        obj = ac_tester.TestClass()
+        meth = obj.meth_method_no_params
+        check = partial(self.assertRaisesRegex, TypeError, "no arguments")
+        check(meth, 1)
+        check(meth, a=1)
+
+    def test_meth_method_no_params_capi(self):
+        from _testcapi import pyobject_vectorcall
+        obj = ac_tester.TestClass()
+        meth = obj.meth_method_no_params
+        pyobject_vectorcall(meth, None, None)
+        pyobject_vectorcall(meth, (), None)
+        pyobject_vectorcall(meth, (), ())
+        pyobject_vectorcall(meth, None, ())
+
+        check = partial(self.assertRaisesRegex, TypeError, "no arguments")
+        check(pyobject_vectorcall, meth, (1,), None)
+        check(pyobject_vectorcall, meth, (1,), ("a",))
+
     def test_depr_star_new(self):
         cls = ac_tester.DeprStarNew
         cls()

Misc/NEWS.d/next/Tools-Demos/2024-02-05-02-45-51.gh-issue-115015.rgtiDB.rst

@@ -0,0 +1,5 @@
+Fix a bug in Argument Clinic that generated incorrect code for methods with
+no parameters that use the :ref:`METH_METHOD | METH_FASTCALL | METH_KEYWORDS
+<METH_METHOD-METH_FASTCALL-METH_KEYWORDS>` calling convention. Only the
+positional parameter count was checked; any keyword argument passed would be
+silently accepted.

Modules/_io/clinic/bufferedio.c.h

@@ -1213,6 +1213,40 @@ clone_with_conv_f2_impl(PyObject *module, custom_t path)
 }
 
 
+/*[clinic input]
+class _testclinic.TestClass "PyObject *" "PyObject"
+[clinic start generated code]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=668a591c65bec947]*/
+
+/*[clinic input]
+_testclinic.TestClass.meth_method_no_params
+    cls: defining_class
+    /
+[clinic start generated code]*/
+
+static PyObject *
+_testclinic_TestClass_meth_method_no_params_impl(PyObject *self,
+                                                 PyTypeObject *cls)
+/*[clinic end generated code: output=c140f100080c2fc8 input=6bd34503d11c63c1]*/
+{
+    Py_RETURN_NONE;
+}
+
+static struct PyMethodDef test_class_methods[] = {
+    _TESTCLINIC_TESTCLASS_METH_METHOD_NO_PARAMS_METHODDEF
+    {NULL, NULL}
+};
+
+static PyTypeObject TestClass = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "_testclinic.TestClass",
+    .tp_basicsize = sizeof(PyObject),
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+    .tp_new = PyType_GenericNew,
+    .tp_methods = test_class_methods,
+};
+
+
 /*[clinic input]
 output push
 destination deprstar new file '{dirname}/clinic/_testclinic_depr.c.h'
@@ -1906,6 +1940,9 @@ PyInit__testclinic(void)
     if (m == NULL) {
         return NULL;
     }
+    if (PyModule_AddType(m, &TestClass) < 0) {
+        goto error;
+    }
     if (PyModule_AddType(m, &DeprStarNew) < 0) {
         goto error;
     }