gh-105922: Add PyImport_AddModuleRef() function

* Add tests on PyImport_AddModuleRef(), PyImport_AddModule() and
  PyImport_AddModuleObject().
* pythonrun.c: Replace Py_XNewRef(PyImport_AddModule(name)) with
  PyImport_AddModuleRef(name).

Author: vstinner

Doc/c-api/import.rst

@@ -98,27 +98,40 @@ Importing Modules
    an exception set on failure (the module still exists in this case).
 
 
-.. c:function:: PyObject* PyImport_AddModuleObject(PyObject *name)
+.. c:function:: PyObject* PyImport_AddModuleRef(const char *name)
+
+   Return the module object corresponding to a module name.
+
+   The *name* argument may be of the form ``package.module``. First check the
+   modules dictionary if there's one there, and if not, create a new one and
+   insert it in the modules dictionary.
+
+   Return a :term:`strong reference` to the module on success. Return ``NULL``
+   with an exception set on failure.
 
-   Return the module object corresponding to a module name.  The *name* argument
-   may be of the form ``package.module``. First check the modules dictionary if
-   there's one there, and if not, create a new one and insert it in the modules
-   dictionary. Return ``NULL`` with an exception set on failure.
+   The module name *name* is decoded from UTF-8.
 
-   .. note::
+   This function does not load or import the module; if the module wasn't
+   already loaded, you will get an empty module object. Use
+   :c:func:`PyImport_ImportModule` or one of its variants to import a module.
+   Package structures implied by a dotted name for *name* are not created if
+   not already present.
+
+   .. versionadded:: 3.13
+
+
+.. c:function:: PyObject* PyImport_AddModuleObject(PyObject *name)
 
-      This function does not load or import the module; if the module wasn't already
-      loaded, you will get an empty module object. Use :c:func:`PyImport_ImportModule`
-      or one of its variants to import a module.  Package structures implied by a
-      dotted name for *name* are not created if not already present.
+   Similar to :c:func:`PyImport_AddModuleRef`, but return a :term:`borrowed
+   reference` and *name* is a Python :class:`str` object.
 
    .. versionadded:: 3.3
 
 
 .. c:function:: PyObject* PyImport_AddModule(const char *name)
 
-   Similar to :c:func:`PyImport_AddModuleObject`, but the name is a UTF-8
-   encoded string instead of a Unicode object.
+   Similar to :c:func:`PyImport_AddModuleRef`, but return a :term:`borrowed
+   reference`.
 
 
 .. c:function:: PyObject* PyImport_ExecCodeModule(const char *name, PyObject *co)

Doc/data/refcounts.dat

@@ -974,6 +974,9 @@ PyCoro_New:PyFrameObject*:frame:0:
 PyCoro_New:PyObject*:name:0:
 PyCoro_New:PyObject*:qualname:0:
 
+PyImport_AddModuleRef:PyObject*::+1:
+PyImport_AddModuleRef:const char*:name::
+
 PyImport_AddModule:PyObject*::0:reference borrowed from sys.modules
 PyImport_AddModule:const char*:name::
 

Doc/data/stable_abi.dat

@@ -426,6 +426,11 @@ New Features
   APIs accepting the format codes always use ``Py_ssize_t`` for ``#`` formats.
   (Contributed by Inada Naoki in :gh:`104922`.)
 
+* Add :c:func:`PyImport_AddModuleRef`: similar to
+  :c:func:`PyImport_AddModule`, but return a :term:`strong reference` instead
+  of a :term:`borrowed reference`.
+  (Contributed by Victor Stinner in :gh:`105922`.)
+
 
 Porting to Python 3.13
 ----------------------

Doc/whatsnew/3.13.rst

@@ -43,6 +43,11 @@ PyAPI_FUNC(PyObject *) PyImport_AddModuleObject(
 PyAPI_FUNC(PyObject *) PyImport_AddModule(
     const char *name            /* UTF-8 encoded string */
     );
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030d0000
+PyAPI_FUNC(PyObject *) PyImport_AddModuleRef(
+    const char *name            /* UTF-8 encoded string */
+    );
+#endif
 PyAPI_FUNC(PyObject *) PyImport_ImportModule(
     const char *name            /* UTF-8 encoded string */
     );

Include/import.h

@@ -2621,6 +2621,30 @@ def test_basic_multiple_interpreters_reset_each(self):
         #  * module's global state was initialized, not reset
 
 
+@cpython_only
+class CAPITests(unittest.TestCase):
+    def test_pyimport_addmodule(self):
+        # gh-105922: Test PyImport_AddModuleRef(), PyImport_AddModule()
+        # and PyImport_AddModuleObject()
+        import _testcapi
+        for name in (
+            'sys',     # frozen module
+            'test',    # package
+            __name__,  # package.module
+        ):
+            _testcapi.check_pyimport_addmodule(name)
+
+    def test_pyimport_addmodule_create(self):
+        # gh-105922: Test PyImport_AddModuleRef(), create a new module
+        import _testcapi
+        name = 'dontexist'
+        self.assertNotIn(name, sys.modules)
+        self.addCleanup(unload, name)
+
+        mod = _testcapi.check_pyimport_addmodule(name)
+        self.assertIs(mod, sys.modules[name])
+
+
 if __name__ == '__main__':
     # Test needs to be a package, so we can do relative imports.
     unittest.main()

Lib/test/test_import/__init__.py

@@ -0,0 +1,3 @@
+Add :c:func:`PyImport_AddModuleRef`: similar to :c:func:`PyImport_AddModule`,
+but return a :term:`strong reference` instead of a :term:`borrowed reference`.
+Patch by Victor Stinner.

Lib/test/test_stable_abi_ctypes.py

@@ -2428,3 +2428,5 @@
     added = '3.12'
 [const.Py_TPFLAGS_ITEMS_AT_END]
     added = '3.12'
+[function.PyImport_AddModuleRef]
+    added = '3.13'

Misc/NEWS.d/next/C API/2023-06-19-20-02-16.gh-issue-105922.o4T6wO.rst

@@ -3325,6 +3325,53 @@ test_atexit(PyObject *self, PyObject *Py_UNUSED(args))
 }
 
 
+static PyObject *
+check_pyimport_addmodule(PyObject *self, PyObject *args)
+{
+    const char *name;
+    if (!PyArg_ParseTuple(args, "s", &name)) {
+        return NULL;
+    }
+
+    // test PyImport_AddModuleRef()
+    PyObject *module = PyImport_AddModuleRef(name);
+    if (module == NULL) {
+        return NULL;
+    }
+    assert(PyModule_Check(module));
+    // module is a strong reference
+
+    // test PyImport_AddModule()
+    PyObject *module2 = PyImport_AddModule(name);
+    if (module2 == NULL) {
+        goto error;
+    }
+    assert(PyModule_Check(module2));
+    assert(module2 == module);
+    // module2 is a borrowed ref
+
+    // test PyImport_AddModuleObject()
+    PyObject *name_obj = PyUnicode_FromString(name);
+    if (name_obj == NULL) {
+        goto error;
+    }
+    PyObject *module3 = PyImport_AddModuleObject(name_obj);
+    Py_DECREF(name_obj);
+    if (module3 == NULL) {
+        goto error;
+    }
+    assert(PyModule_Check(module3));
+    assert(module3 == module);
+    // module3 is a borrowed ref
+
+    return module;
+
+error:
+    Py_DECREF(module);
+    return NULL;
+}
+
+
 static PyMethodDef TestMethods[] = {
     {"set_errno",               set_errno,                       METH_VARARGS},
     {"test_config",             test_config,                     METH_NOARGS},
@@ -3468,6 +3515,7 @@ static PyMethodDef TestMethods[] = {
     {"function_get_kw_defaults", function_get_kw_defaults, METH_O, NULL},
     {"function_set_kw_defaults", function_set_kw_defaults, METH_VARARGS, NULL},
     {"test_atexit", test_atexit, METH_NOARGS},
+    {"check_pyimport_addmodule", check_pyimport_addmodule, METH_VARARGS},
     {NULL, NULL} /* sentinel */
 };