gh-107880: Teach Argument Clinic to clone __init__ and __new__ methods

Lib/test/test_clinic.py

@@ -2973,6 +2973,17 @@ def test_depr_star_new(self):
             ac_tester.DeprStarNew(None)
         self.assertEqual(cm.filename, __file__)
 
+    def test_depr_star_new_cloned(self):
+        regex = re.escape(
+            "Passing positional arguments to _testclinic.DeprStarNew.cloned() "
+            "is deprecated. Parameter 'a' will become a keyword-only parameter "
+            "in Python 3.14."
+        )
+        obj = ac_tester.DeprStarNew(a=None)
+        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
+            obj.cloned(None)
+        self.assertEqual(cm.filename, __file__)
+
     def test_depr_star_init(self):
         regex = re.escape(
             "Passing positional arguments to _testclinic.DeprStarInit() is "
@@ -2983,6 +2994,17 @@ def test_depr_star_init(self):
             ac_tester.DeprStarInit(None)
         self.assertEqual(cm.filename, __file__)
 
+    def test_depr_star_init_cloned(self):
+        regex = re.escape(
+            "Passing positional arguments to _testclinic.DeprStarInit.cloned() "
+            "is deprecated. Parameter 'a' will become a keyword-only parameter "
+            "in Python 3.14."
+        )
+        obj = ac_tester.DeprStarInit(a=None)
+        with self.assertWarnsRegex(DeprecationWarning, regex) as cm:
+            obj.cloned(None)
+        self.assertEqual(cm.filename, __file__)
+
     def test_depr_star_pos0_len1(self):
         fn = ac_tester.depr_star_pos0_len1
         fn(a=None)

Misc/NEWS.d/next/Tools-Demos/2023-08-13-11-18-06.gh-issue-107880.gBVVQ7.rst

@@ -0,0 +1,2 @@
+Argument Clinic can now clone :meth:`!__init__` and :meth:`!__new__`
+methods.

Modules/_testclinic.c

@@ -1230,12 +1230,29 @@ depr_star_new_impl(PyTypeObject *type, PyObject *a)
     return type->tp_alloc(type, 0);
 }
 
+/*[clinic input]
+_testclinic.DeprStarNew.cloned as depr_star_new_clone = _testclinic.DeprStarNew.__new__
+[clinic start generated code]*/
+
+static PyObject *
+depr_star_new_clone_impl(PyObject *type, PyObject *a)
+/*[clinic end generated code: output=3b17bf885fa736bc input=ea659285d5dbec6c]*/
+{
+    Py_RETURN_NONE;
+}
+
+static struct PyMethodDef depr_star_new_methods[] = {
+    DEPR_STAR_NEW_CLONE_METHODDEF
+    {NULL, NULL}
+};
+
 static PyTypeObject DeprStarNew = {
     PyVarObject_HEAD_INIT(NULL, 0)
     .tp_name = "_testclinic.DeprStarNew",
     .tp_basicsize = sizeof(PyObject),
     .tp_new = depr_star_new,
     .tp_flags = Py_TPFLAGS_DEFAULT,
+    .tp_methods = depr_star_new_methods,
 };
 
 
@@ -1254,13 +1271,30 @@ depr_star_init_impl(PyObject *self, PyObject *a)
     return 0;
 }
 
+/*[clinic input]
+_testclinic.DeprStarInit.cloned as depr_star_init_clone = _testclinic.DeprStarInit.__init__
+[clinic start generated code]*/
+
+static PyObject *
+depr_star_init_clone_impl(PyObject *self, PyObject *a)
+/*[clinic end generated code: output=ddfe8a1b5531e7cc input=561e103fe7f8e94f]*/
+{
+    Py_RETURN_NONE;
+}
+
+static struct PyMethodDef depr_star_init_methods[] = {
+    DEPR_STAR_INIT_CLONE_METHODDEF
+    {NULL, NULL}
+};
+
 static PyTypeObject DeprStarInit = {
     PyVarObject_HEAD_INIT(NULL, 0)
     .tp_name = "_testclinic.DeprStarInit",
     .tp_basicsize = sizeof(PyObject),
     .tp_new = PyType_GenericNew,
     .tp_init = depr_star_init,
     .tp_flags = Py_TPFLAGS_DEFAULT,
+    .tp_methods = depr_star_init_methods,
 };
 
 

Tools/clinic/clinic.py

@@ -4888,13 +4888,25 @@ def state_modulename_name(self, line: str) -> None:
                 function_name = fields.pop()
                 module, cls = self.clinic._module_and_class(fields)
 
-                if not (existing_function.kind is self.kind and existing_function.coexist == self.coexist):
-                    fail("'kind' of function and cloned function don't match! "
-                         "(@classmethod/@staticmethod/@coexist)")
-                function = existing_function.copy(
-                    name=function_name, full_name=full_name, module=module,
-                    cls=cls, c_basename=c_basename, docstring=''
-                )
+                overrides: dict[str, Any] = {
+                    "name": function_name,
+                    "full_name": full_name,
+                    "module": module,
+                    "cls": cls,
+                    "c_basename": c_basename,
+                    "docstring": "",
+                }
+                if not (existing_function.kind is self.kind and
+                        existing_function.coexist == self.coexist):
+                    # Allow __new__ or __init__ methods.
+                    if existing_function.kind.new_or_init:
+                        overrides["kind"] = self.kind
+                        # Future enhancement: allow custom return converters
+                        overrides["return_converter"] = CReturnConverter()
+                    else:
+                        fail("'kind' of function and cloned function don't match! "
+                             "(@classmethod/@staticmethod/@coexist)")
+                function = existing_function.copy(**overrides)
                 self.function = function
                 self.block.signatures.append(function)
                 (cls or module).functions.append(function)