pythongh-120782: Update internal type cache when reloading datetime (python#120829)

Author: neonene

Lib/test/datetimetester.py

@@ -6870,6 +6870,23 @@ def pickle_fake_date(datetime_) -> Type[FakeDate]:
                 """)
             script_helper.assert_python_ok('-c', script)
 
+    def test_update_type_cache(self):
+        # gh-120782
+        script = textwrap.dedent("""
+            import sys
+            for i in range(5):
+                import _datetime
+                _datetime.date.max > _datetime.date.min
+                _datetime.time.max > _datetime.time.min
+                _datetime.datetime.max > _datetime.datetime.min
+                _datetime.timedelta.max > _datetime.timedelta.min
+                isinstance(_datetime.timezone.min, _datetime.tzinfo)
+                isinstance(_datetime.timezone.utc, _datetime.tzinfo)
+                isinstance(_datetime.timezone.max, _datetime.tzinfo)
+                del sys.modules['_datetime']
+            """)
+        script_helper.assert_python_ok('-c', script)
+
 
 def load_tests(loader, standard_tests, pattern):
     standard_tests.addTest(ZoneInfoCompleteTest())

Misc/NEWS.d/next/Library/2024-06-21-12-00-16.gh-issue-120782.LOE8tj.rst

@@ -0,0 +1 @@
+Fix wrong references of the :mod:`datetime` types after reloading the module.

Modules/_datetimemodule.c

@@ -7296,6 +7296,12 @@ _datetime_exec(PyObject *module)
     static_assert(DI100Y == 25 * DI4Y - 1, "DI100Y");
     assert(DI100Y == days_before_year(100+1));
 
+    if (reloading) {
+        for (size_t i = 0; i < Py_ARRAY_LENGTH(capi_types); i++) {
+            PyType_Modified(capi_types[i]);
+        }
+    }
+
     if (set_current_module(interp, module) < 0) {
         goto error;
     }