gh-117398: Add datetime C-API type check test for subinterpreters

Lib/test/test_capi/test_misc.py

@@ -2285,6 +2285,24 @@ def test_module_state_shared_in_global(self):
         subinterp_attr_id = os.read(r, 100)
         self.assertEqual(main_attr_id, subinterp_attr_id)
 
+    @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+    def test_datetime_capi_type_check(self):
+        script = textwrap.dedent("""
+            import importlib.machinery
+            import importlib.util
+            fullname = '_test_datetime_capi_client'
+            origin = importlib.util.find_spec('_testmultiphase').origin
+            loader = importlib.machinery.ExtensionFileLoader(fullname, origin)
+            spec = importlib.util.spec_from_loader(fullname, loader)
+            module = importlib.util.module_from_spec(spec)
+            spec.loader.exec_module(module)
+            import datetime
+            module.pydate_check(datetime.date.today())
+        """)
+        exec(script)
+        ret = support.run_in_subinterp(script)
+        self.assertEqual(ret, 0)
+
 
 @requires_subinterpreters
 class InterpreterConfigTests(unittest.TestCase):

Modules/_testmultiphase.c

@@ -969,3 +969,43 @@ PyInit__test_shared_gil_only(void)
 {
     return PyModuleDef_Init(&shared_gil_only_def);
 }
+
+
+#include "datetime.h"
+
+static PyObject *
+datetime_capi_pydate_check(PyObject *self, PyObject *op)
+{
+    PyDateTime_IMPORT;
+#ifdef Py_GIL_DISABLED
+    if (!PyDateTimeAPI && PyInterpreterState_Get() != PyInterpreterState_Main()) {
+        // Subinterpreter cannot import lagacy _datetime module and capsule.
+        PyErr_WriteUnraisable(NULL);
+        Py_RETURN_NONE;
+    }
+#endif
+    if (PyDate_Check(op)) {
+        Py_RETURN_NONE;
+    }
+    PyErr_SetString(PyExc_TypeError, "object is not instance of capi type");
+    return NULL;
+}
+
+static PyMethodDef datetime_capi_client_methods[] = {
+    {"pydate_check", datetime_capi_pydate_check, METH_O, NULL},
+    {0},
+};
+
+static PyModuleDef_Slot datetime_capi_client_slots[] = {
+    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
+    {0, NULL},
+};
+
+static PyModuleDef datetime_capi_client_def = TEST_MODULE_DEF(
+    "_testmultiphase_datetime_capi_client", datetime_capi_client_slots, datetime_capi_client_methods);
+
+PyMODINIT_FUNC
+PyInit__test_datetime_capi_client(void)
+{
+    return PyModuleDef_Init(&datetime_capi_client_def);
+}