gh-116146: Add C-API to create module from spec and initfunc (GH-139196)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>

Programs/_testembed.c

@@ -166,6 +166,8 @@ static PyModuleDef embedded_ext = {
 static PyObject*
 PyInit_embedded_ext(void)
 {
+    // keep this as a single-phase initialization module;
+    // see test_create_module_from_initfunc
     return PyModule_Create(&embedded_ext);
 }
 
@@ -1894,8 +1896,16 @@ static int test_initconfig_exit(void)
 }
 
 
+int
+extension_module_exec(PyObject *mod)
+{
+    return PyModule_AddStringConstant(mod, "exec_slot_ran", "yes");
+}
+
+
 static PyModuleDef_Slot extension_slots[] = {
     {Py_mod_gil, Py_MOD_GIL_NOT_USED},
+    {Py_mod_exec, extension_module_exec},
     {0, NULL}
 };
 
@@ -2213,6 +2223,106 @@ static int test_repeated_init_and_inittab(void)
     return 0;
 }
 
+static PyObject*
+create_module(PyObject* self, PyObject* spec)
+{
+    PyObject *name = PyObject_GetAttrString(spec, "name");
+    if (!name) {
+        return NULL;
+    }
+    if (PyUnicode_EqualToUTF8(name, "my_test_extension")) {
+        Py_DECREF(name);
+        return PyImport_CreateModuleFromInitfunc(spec, init_my_test_extension);
+    }
+    if (PyUnicode_EqualToUTF8(name, "embedded_ext")) {
+        Py_DECREF(name);
+        return PyImport_CreateModuleFromInitfunc(spec, PyInit_embedded_ext);
+    }
+    PyErr_Format(PyExc_LookupError, "static module %R not found", name);
+    Py_DECREF(name);
+    return NULL;
+}
+
+static PyObject*
+exec_module(PyObject* self, PyObject* mod)
+{
+    if (PyModule_Exec(mod) < 0) {
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
+
+static PyMethodDef create_static_module_methods[] = {
+    {"create_module", create_module, METH_O, NULL},
+    {"exec_module", exec_module, METH_O, NULL},
+    {}
+};
+
+static struct PyModuleDef create_static_module_def = {
+    PyModuleDef_HEAD_INIT,
+    .m_name = "create_static_module",
+    .m_size = 0,
+    .m_methods = create_static_module_methods,
+    .m_slots = extension_slots,
+};
+
+PyMODINIT_FUNC PyInit_create_static_module(void) {
+    return PyModuleDef_Init(&create_static_module_def);
+}
+
+static int
+test_create_module_from_initfunc(void)
+{
+    wchar_t* argv[] = {
+        PROGRAM_NAME,
+        L"-c",
+        // Multi-phase initialization
+        L"import my_test_extension;"
+        L"print(my_test_extension);"
+        L"print(f'{my_test_extension.executed=}');"
+        L"print(f'{my_test_extension.exec_slot_ran=}');"
+        // Single-phase initialization
+        L"import embedded_ext;"
+        L"print(embedded_ext);"
+        L"print(f'{embedded_ext.executed=}');"
+    };
+    PyConfig config;
+    if (PyImport_AppendInittab("create_static_module",
+                               &PyInit_create_static_module) != 0) {
+        fprintf(stderr, "PyImport_AppendInittab() failed\n");
+        return 1;
+    }
+    PyConfig_InitPythonConfig(&config);
+    config.isolated = 1;
+    config_set_argv(&config, Py_ARRAY_LENGTH(argv), argv);
+    init_from_config_clear(&config);
+    int result = PyRun_SimpleString(
+        "import sys\n"
+        "from importlib.util import spec_from_loader\n"
+        "import create_static_module\n"
+        "class StaticExtensionImporter:\n"
+        "   _ORIGIN = \"static-extension\"\n"
+        "   @classmethod\n"
+        "   def find_spec(cls, fullname, path, target=None):\n"
+        "       if fullname in {'my_test_extension', 'embedded_ext'}:\n"
+        "           return spec_from_loader(fullname, cls, origin=cls._ORIGIN)\n"
+        "       return None\n"
+        "   @staticmethod\n"
+        "   def create_module(spec):\n"
+        "       return create_static_module.create_module(spec)\n"
+        "   @staticmethod\n"
+        "   def exec_module(module):\n"
+        "       create_static_module.exec_module(module)\n"
+        "       module.executed = 'yes'\n"
+        "sys.meta_path.append(StaticExtensionImporter)\n"
+    );
+    if (result < 0) {
+        fprintf(stderr, "PyRun_SimpleString() failed\n");
+        return 1;
+    }
+    return Py_RunMain();
+}
+
 static void wrap_allocator(PyMemAllocatorEx *allocator);
 static void unwrap_allocator(PyMemAllocatorEx *allocator);
 
@@ -2396,6 +2506,7 @@ static struct TestCase TestCases[] = {
 #endif
     {"test_get_incomplete_frame", test_get_incomplete_frame},
     {"test_gilstate_after_finalization", test_gilstate_after_finalization},
+    {"test_create_module_from_initfunc", test_create_module_from_initfunc},
     {NULL, NULL}
 };