gh-152298: Propagate lazy submodule errors

Author: 1sgtpepper

Include/internal/pycore_import.h

@@ -39,8 +39,10 @@ extern PyObject * _PyImport_GetAbsName(
 // Symbol is exported for the JIT on Windows builds.
 PyAPI_FUNC(PyObject *) _PyImport_LoadLazyImportTstate(
     PyThreadState *tstate, PyObject *lazy_import);
-extern PyObject * _PyImport_TryLoadLazySubmodule(
-    PyObject *mod_name, PyObject *attr_name, PyObject *mod_dict);
+// Returns 1 with a new reference in result, 0 if not pending, or -1 on error.
+extern int _PyImport_TryLoadLazySubmodule(
+    PyObject *mod_name, PyObject *attr_name, PyObject *mod_dict,
+    PyObject **result);
 extern PyObject * _PyImport_LazyImportModuleLevelObject(
     PyThreadState *tstate, PyObject *name, PyObject *builtins,
     PyObject *globals, PyObject *locals, PyObject *fromlist, int level);

Objects/moduleobject.c

@@ -1300,7 +1300,7 @@ _PyModule_IsPossiblyShadowing(PyObject *origin)
 }
 
 // Check if `name` is a lazily pending submodule of module `m`.
-// Returns a new reference on success, or NULL with no error set.
+// Returns a new reference on success, or NULL on miss or error.
 static PyObject *
 try_load_lazy_submodule(PyModuleObject *m, PyObject *name)
 {
@@ -1313,11 +1313,11 @@ try_load_lazy_submodule(PyModuleObject *m, PyObject *name)
         Py_DECREF(mod_name);
         return NULL;
     }
-    PyObject *result = _PyImport_TryLoadLazySubmodule(
-        mod_name, name, m->md_dict);
+    PyObject *result = NULL;
+    int lazy_rc = _PyImport_TryLoadLazySubmodule(
+        mod_name, name, m->md_dict, &result);
     Py_DECREF(mod_name);
-    if (result == NULL) {
-        PyErr_Clear();
+    if (lazy_rc <= 0) {
         return NULL;
     }
     return result;

Python/import.c

@@ -4452,63 +4452,73 @@ register_from_lazy_on_parent(PyThreadState *tstate, PyObject *abs_name,
     return res;
 }
 
-PyObject *
+int
 _PyImport_TryLoadLazySubmodule(PyObject *mod_name, PyObject *attr_name,
-                               PyObject *mod_dict)
+                               PyObject *mod_dict, PyObject **result)
 {
+    *result = NULL;
+
     PyInterpreterState *interp = _PyInterpreterState_GET();
     PyObject *lazy_pending = LAZY_PENDING_SUBMODULES(interp);
     if (lazy_pending == NULL) {
-        return NULL;
+        return 0;
     }
 
     PyObject *pending_set;
     int rc = PyDict_GetItemRef(lazy_pending, mod_name, &pending_set);
-    if (rc <= 0) {
-        return NULL;
+    if (rc < 0) {
+        return -1;
+    }
+    if (rc == 0) {
+        return 0;
     }
 
     int contains = PySet_Contains(pending_set, attr_name);
-    if (contains <= 0) {
+    if (contains < 0) {
         Py_DECREF(pending_set);
-        return NULL;
+        return -1;
+    }
+    if (contains == 0) {
+        Py_DECREF(pending_set);
+        return 0;
     }
 
     PyObject *full_name = PyUnicode_FromFormat("%U.%U", mod_name, attr_name);
     if (full_name == NULL) {
         Py_DECREF(pending_set);
-        return NULL;
+        return -1;
     }
 
     PyObject *mod = PyImport_ImportModuleLevelObject(
         full_name, NULL, NULL, NULL, 0);
     if (mod == NULL) {
         Py_DECREF(pending_set);
         Py_DECREF(full_name);
-        return NULL;
+        return -1;
     }
     Py_DECREF(mod);
 
     PyObject *submod = PyImport_GetModule(full_name);
     Py_DECREF(full_name);
     if (submod == NULL) {
         Py_DECREF(pending_set);
-        return NULL;
+        return -1;
     }
 
     if (PyDict_SetItem(mod_dict, attr_name, submod) < 0) {
         Py_DECREF(pending_set);
         Py_DECREF(submod);
-        return NULL;
+        return -1;
     }
 
     if (PySet_Discard(pending_set, attr_name) < 0) {
         Py_DECREF(pending_set);
         Py_DECREF(submod);
-        return NULL;
+        return -1;
     }
     Py_DECREF(pending_set);
-    return submod;
+    *result = submod;
+    return 1;
 }
 
 PyObject *