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gh-94808: cover PyFunction_GetDefaults and PyFunction_SetDefaults #98449

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Oct 27, 2022
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42 changes: 42 additions & 0 deletions Lib/test/test_capi.py
Original file line number Diff line number Diff line change
Expand Up @@ -930,6 +930,48 @@ def some():
with self.assertRaises(SystemError):
_testcapi.function_get_module(None) # not a function

def test_function_get_defaults(self):
def some(pos_only='p', zero=0, optional=None):
pass

defaults = _testcapi.function_get_defaults(some)
self.assertEqual(defaults, ('p', 0, None))
self.assertEqual(defaults, some.__defaults__)

with self.assertRaises(SystemError):
_testcapi.function_get_module(None) # not a function

def test_function_set_defaults(self):
def some(pos_only='p', zero=0, optional=None):
pass

old_defaults = ('p', 0, None)
self.assertEqual(_testcapi.function_get_defaults(some), old_defaults)
self.assertEqual(some.__defaults__, old_defaults)

with self.assertRaises(SystemError):
_testcapi.function_set_defaults(some, 1) # not tuple or None
self.assertEqual(_testcapi.function_get_defaults(some), old_defaults)
self.assertEqual(some.__defaults__, old_defaults)

new_defaults = ('q', 1, None)
_testcapi.function_set_defaults(some, new_defaults)
self.assertEqual(_testcapi.function_get_defaults(some), new_defaults)
self.assertEqual(some.__defaults__, new_defaults)

class tuplesub(tuple): ... # tuple subclasses must work

new_defaults = tuplesub(((1, 2), ['a', 'b'], None))
_testcapi.function_set_defaults(some, new_defaults)
self.assertEqual(_testcapi.function_get_defaults(some), new_defaults)
self.assertEqual(some.__defaults__, new_defaults)

# `None` is special, it sets `defaults` to `NULL`,
# it needs special handling in `_testcapi`:
_testcapi.function_set_defaults(some, None)
self.assertEqual(_testcapi.function_get_defaults(some), None)
self.assertEqual(some.__defaults__, None)


class TestPendingCalls(unittest.TestCase):

Expand Down
29 changes: 29 additions & 0 deletions Modules/_testcapimodule.c
Original file line number Diff line number Diff line change
Expand Up @@ -5694,6 +5694,33 @@ function_get_module(PyObject *self, PyObject *func)
}
}

static PyObject *
function_get_defaults(PyObject *self, PyObject *func)
{
PyObject *defaults = PyFunction_GetDefaults(func);
if (defaults != NULL) {
Py_INCREF(defaults);
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This is correct because PyFunction_GetDefaults returns a borrowed ref.

return defaults;
} else if (PyErr_Occurred()) {
return NULL;
} else {
Py_RETURN_NONE; // This can happen when `defaults` are set to `None`
}
}

static PyObject *
function_set_defaults(PyObject *self, PyObject *args)
{
PyObject *func = NULL, *defaults = NULL;
if (!PyArg_ParseTuple(args, "OO", &func, &defaults)) {
return NULL;
}
int result = PyFunction_SetDefaults(func, defaults);
if (result == -1)
return NULL;
Py_RETURN_NONE;
}


// type watchers

Expand Down Expand Up @@ -6103,6 +6130,8 @@ static PyMethodDef TestMethods[] = {
{"function_get_code", function_get_code, METH_O, NULL},
{"function_get_globals", function_get_globals, METH_O, NULL},
{"function_get_module", function_get_module, METH_O, NULL},
{"function_get_defaults", function_get_defaults, METH_O, NULL},
{"function_set_defaults", function_set_defaults, METH_VARARGS, NULL},
{"add_type_watcher", add_type_watcher, METH_O, NULL},
{"clear_type_watcher", clear_type_watcher, METH_O, NULL},
{"watch_type", watch_type, METH_VARARGS, NULL},
Expand Down