gh-112640: Add `kwdefaults` parameter to `types.FunctionType.__new__` (#112641)

Include/internal/pycore_global_objects_fini_generated.h

@@ -1015,6 +1015,7 @@ _PyStaticObjects_CheckRefcnt(PyInterpreterState *interp) {
     _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(kw));
     _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(kw1));
     _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(kw2));
+    _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(kwdefaults));
     _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(lambda));
     _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(last));
     _PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(last_exc));

Include/internal/pycore_global_strings.h

@@ -504,6 +504,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(kw)
         STRUCT_FOR_ID(kw1)
         STRUCT_FOR_ID(kw2)
+        STRUCT_FOR_ID(kwdefaults)
         STRUCT_FOR_ID(lambda)
         STRUCT_FOR_ID(last)
         STRUCT_FOR_ID(last_exc)

Include/internal/pycore_runtime_init_generated.h

@@ -1013,6 +1013,7 @@ extern "C" {
     INIT_ID(kw), \
     INIT_ID(kw1), \
     INIT_ID(kw2), \
+    INIT_ID(kwdefaults), \
     INIT_ID(lambda), \
     INIT_ID(last), \
     INIT_ID(last_exc), \

Include/internal/pycore_unicodeobject_generated.h

@@ -1353,6 +1353,9 @@ _PyUnicode_InitStaticStrings(PyInterpreterState *interp) {
     string = &_Py_ID(kw2);
     assert(_PyUnicode_CheckConsistency(string, 1));
     _PyUnicode_InternInPlace(interp, &string);
+    string = &_Py_ID(kwdefaults);
+    assert(_PyUnicode_CheckConsistency(string, 1));
+    _PyUnicode_InternInPlace(interp, &string);
     string = &_Py_ID(lambda);
     assert(_PyUnicode_CheckConsistency(string, 1));
     _PyUnicode_InternInPlace(interp, &string);

Lib/test/test_types.py

@@ -2263,5 +2263,38 @@ class CoroutineTests(unittest.TestCase):
             'close', 'throw'}))
 
 
+class FunctionTests(unittest.TestCase):
+    def test_function_type_defaults(self):
+        def ex(a, /, b, *, c):
+            return a + b + c
+
+        func = types.FunctionType(
+            ex.__code__, {}, "func", (1, 2), None, {'c': 3},
+        )
+
+        self.assertEqual(func(), 6)
+        self.assertEqual(func.__defaults__, (1, 2))
+        self.assertEqual(func.__kwdefaults__, {'c': 3})
+
+        func = types.FunctionType(
+            ex.__code__, {}, "func", None, None, None,
+        )
+        self.assertEqual(func.__defaults__, None)
+        self.assertEqual(func.__kwdefaults__, None)
+
+    def test_function_type_wrong_defaults(self):
+        def ex(a, /, b, *, c):
+            return a + b + c
+
+        with self.assertRaisesRegex(TypeError, 'arg 4'):
+            types.FunctionType(
+                ex.__code__, {}, "func", 1, None, {'c': 3},
+            )
+        with self.assertRaisesRegex(TypeError, 'arg 6'):
+            types.FunctionType(
+                ex.__code__, {}, "func", None, None, 3,
+            )
+
+
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2023-12-03-11-15-53.gh-issue-112640.-FVwP7.rst

@@ -0,0 +1,2 @@
+Add ``kwdefaults`` parameter to :data:`types.FunctionType` to set
+default keyword argument values.

Objects/clinic/funcobject.c.h

@@ -9,7 +9,8 @@ preserve
 #include "pycore_modsupport.h"    // _PyArg_UnpackKeywords()
 
 PyDoc_STRVAR(func_new__doc__,
-"function(code, globals, name=None, argdefs=None, closure=None)\n"
+"function(code, globals, name=None, argdefs=None, closure=None,\n"
+"         kwdefaults=None)\n"
 "--\n"
 "\n"
 "Create a function object.\n"
@@ -23,11 +24,14 @@ PyDoc_STRVAR(func_new__doc__,
 "  argdefs\n"
 "    a tuple that specifies the default argument values\n"
 "  closure\n"
-"    a tuple that supplies the bindings for free variables");
+"    a tuple that supplies the bindings for free variables\n"
+"  kwdefaults\n"
+"    a dictionary that specifies the default keyword argument values");
 
 static PyObject *
 func_new_impl(PyTypeObject *type, PyCodeObject *code, PyObject *globals,
-              PyObject *name, PyObject *defaults, PyObject *closure);
+              PyObject *name, PyObject *defaults, PyObject *closure,
+              PyObject *kwdefaults);
 
 static PyObject *
 func_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
@@ -35,14 +39,14 @@ func_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
     PyObject *return_value = NULL;
     #if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
 
-    #define NUM_KEYWORDS 5
+    #define NUM_KEYWORDS 6
     static struct {
         PyGC_Head _this_is_not_used;
         PyObject_VAR_HEAD
         PyObject *ob_item[NUM_KEYWORDS];
     } _kwtuple = {
         .ob_base = PyVarObject_HEAD_INIT(&PyTuple_Type, NUM_KEYWORDS)
-        .ob_item = { &_Py_ID(code), &_Py_ID(globals), &_Py_ID(name), &_Py_ID(argdefs), &_Py_ID(closure), },
+        .ob_item = { &_Py_ID(code), &_Py_ID(globals), &_Py_ID(name), &_Py_ID(argdefs), &_Py_ID(closure), &_Py_ID(kwdefaults), },
     };
     #undef NUM_KEYWORDS
     #define KWTUPLE (&_kwtuple.ob_base.ob_base)
@@ -51,14 +55,14 @@ func_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
     #  define KWTUPLE NULL
     #endif  // !Py_BUILD_CORE
 
-    static const char * const _keywords[] = {"code", "globals", "name", "argdefs", "closure", NULL};
+    static const char * const _keywords[] = {"code", "globals", "name", "argdefs", "closure", "kwdefaults", NULL};
     static _PyArg_Parser _parser = {
         .keywords = _keywords,
         .fname = "function",
         .kwtuple = KWTUPLE,
     };
     #undef KWTUPLE
-    PyObject *argsbuf[5];
+    PyObject *argsbuf[6];
     PyObject * const *fastargs;
     Py_ssize_t nargs = PyTuple_GET_SIZE(args);
     Py_ssize_t noptargs = nargs + (kwargs ? PyDict_GET_SIZE(kwargs) : 0) - 2;
@@ -67,8 +71,9 @@ func_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
     PyObject *name = Py_None;
     PyObject *defaults = Py_None;
     PyObject *closure = Py_None;
+    PyObject *kwdefaults = Py_None;
 
-    fastargs = _PyArg_UnpackKeywords(_PyTuple_CAST(args)->ob_item, nargs, kwargs, NULL, &_parser, 2, 5, 0, argsbuf);
+    fastargs = _PyArg_UnpackKeywords(_PyTuple_CAST(args)->ob_item, nargs, kwargs, NULL, &_parser, 2, 6, 0, argsbuf);
     if (!fastargs) {
         goto exit;
     }
@@ -97,11 +102,17 @@ func_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
             goto skip_optional_pos;
         }
     }
-    closure = fastargs[4];
+    if (fastargs[4]) {
+        closure = fastargs[4];
+        if (!--noptargs) {
+            goto skip_optional_pos;
+        }
+    }
+    kwdefaults = fastargs[5];
 skip_optional_pos:
-    return_value = func_new_impl(type, code, globals, name, defaults, closure);
+    return_value = func_new_impl(type, code, globals, name, defaults, closure, kwdefaults);
 
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=ff7b995500d2bee6 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=10947342188f38a9 input=a9049054013a1b77]*/

Objects/funcobject.c

@@ -809,14 +809,17 @@ function.__new__ as func_new
         a tuple that specifies the default argument values
     closure: object = None
         a tuple that supplies the bindings for free variables
+    kwdefaults: object = None
+        a dictionary that specifies the default keyword argument values
 
 Create a function object.
 [clinic start generated code]*/
 
 static PyObject *
 func_new_impl(PyTypeObject *type, PyCodeObject *code, PyObject *globals,
-              PyObject *name, PyObject *defaults, PyObject *closure)
+              PyObject *name, PyObject *defaults, PyObject *closure,
-/*[clinic end generated code: output=99c6d9da3a24e3be input=93611752fc2daf11]*/
+              PyObject *kwdefaults)
+/*[clinic end generated code: output=de72f4c22ac57144 input=20c9c9f04ad2d3f2]*/
 {
     PyFunctionObject *newfunc;
     Py_ssize_t nclosure;
@@ -843,6 +846,11 @@ func_new_impl(PyTypeObject *type, PyCodeObject *code, PyObject *globals,
             return NULL;
         }
     }
+    if (kwdefaults != Py_None && !PyDict_Check(kwdefaults)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "arg 6 (kwdefaults) must be None or dict");
+        return NULL;
+    }
 
     /* check that the closure is well-formed */
     nclosure = closure == Py_None ? 0 : PyTuple_GET_SIZE(closure);
@@ -879,6 +887,9 @@ func_new_impl(PyTypeObject *type, PyCodeObject *code, PyObject *globals,
     if (closure != Py_None) {
         newfunc->func_closure = Py_NewRef(closure);
     }
+    if (kwdefaults != Py_None) {
+        newfunc->func_kwdefaults = Py_NewRef(kwdefaults);
+    }
 
     return (PyObject *)newfunc;
 }