Adopt multi-phase init (PEP 489)

Author: AA-Turner

CHANGES.rst

@@ -5,6 +5,8 @@ Unreleased
 
 -   ``__version__`` raises ``DeprecationWarning`` instead of ``UserWarning``.
     :issue:`487`
+-   Adopt multi-phase initialisation (:pep:`489`) for the C extension.
+    :issue:`494`
 
 
 Version 3.0.2

src/markupsafe/_speedups.c

@@ -175,30 +175,26 @@ static PyMethodDef module_methods[] = {
 	{NULL, NULL, 0, NULL}  /* Sentinel */
 };
 
+static PyModuleDef_Slot module_slots[] = {
+#ifdef Py_mod_multiple_interpreters  // Python 3.12+
+	{Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
+#endif
+#ifdef Py_mod_gil  // Python 3.13+
+	{Py_mod_gil, Py_MOD_GIL_NOT_USED},
+#endif
+	{0, NULL}  /* Sentinel */
+};
+
 static struct PyModuleDef module_definition = {
-	PyModuleDef_HEAD_INIT,
-	"markupsafe._speedups",
-	NULL,
-	-1,
-	module_methods,
-	NULL,
-	NULL,
-	NULL,
-	NULL
+	.m_base = PyModuleDef_HEAD_INIT,
+	.m_name = "markupsafe._speedups",
+	.m_size = 0,
+	.m_methods = module_methods,
+	.m_slots = module_slots,
 };
 
 PyMODINIT_FUNC
 PyInit__speedups(void)
 {
-	PyObject *m = PyModule_Create(&module_definition);
-
-	if (m == NULL) {
-		return NULL;
-	}
-
-	#ifdef Py_GIL_DISABLED
-	PyUnstable_Module_SetGIL(m, Py_MOD_GIL_NOT_USED);
-	#endif
-
-	return m;
+	return PyModuleDef_Init(&module_definition);
 }

tests/test_reloading.py

@@ -0,0 +1,38 @@
+import subprocess
+import sys
+
+import pytest
+
+import markupsafe
+
+try:
+    from markupsafe import _speedups
+except ImportError:
+    _speedups = None  # type: ignore
+
+
+@pytest.mark.skipif(_speedups is None, reason="speedups unavailable")
+def test_reload():
+    if markupsafe._escape_inner is not _speedups._escape_inner:
+        pytest.skip("speedups not active")
+
+    code = r"""
+import sys
+import markupsafe._speedups as old
+
+for k in [k for k in sys.modules if k.startswith('markupsafe')]:
+    del sys.modules[k]
+
+import markupsafe._speedups as new
+
+assert old.__dict__ != new.__dict__
+assert old._escape_inner is not new._escape_inner
+"""
+    p = subprocess.run(
+        (sys.executable, "-c", code),
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        encoding="utf-8",
+        check=False,
+    )
+    assert p.returncode == 0, p.stdout