gh-112660: Do not clear arbitrary errors on import (GH-112661)

Previously arbitrary errors could be cleared during formatting error
messages for ImportError or AttributeError for modules. Now all
unexpected errors are reported.

1 files changed, 14 insertions, 11 deletions

diff --git a/Python/import.c b/Python/import.c
index f37393bbdc4..ef81f46a4d6 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -252,18 +252,21 @@ import_ensure_initialized(PyInterpreterState *interp, PyObject *mod, PyObject *n
        NOTE: because of this, initializing must be set *before*
        stuffing the new module in sys.modules.
     */
-    spec = PyObject_GetAttr(mod, &_Py_ID(__spec__));
-    int busy = _PyModuleSpec_IsInitializing(spec);
-    Py_XDECREF(spec);
-    if (busy) {
-        /* Wait until module is done importing. */
-        PyObject *value = PyObject_CallMethodOneArg(
-            IMPORTLIB(interp), &_Py_ID(_lock_unlock_module), name);
-        if (value == NULL) {
-            return -1;
-        }
-        Py_DECREF(value);
+    int rc = PyObject_GetOptionalAttr(mod, &_Py_ID(__spec__), &spec);
+    if (rc > 0) {
+        rc = _PyModuleSpec_IsInitializing(spec);
+        Py_DECREF(spec);
+    }
+    if (rc <= 0) {
+        return rc;
     }
+    /* Wait until module is done importing. */
+    PyObject *value = PyObject_CallMethodOneArg(
+        IMPORTLIB(interp), &_Py_ID(_lock_unlock_module), name);
+    if (value == NULL) {
+        return -1;
+    }
+    Py_DECREF(value);
     return 0;
 }