From c9508f3215b85ac3e9c791de899a783a39f31076 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Mon, 31 May 2021 16:07:50 +0200
Subject: [PATCH] task: Prevent error indicator being sporadically cleared

---
 panda/src/event/asyncFuture_ext.cxx | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/panda/src/event/asyncFuture_ext.cxx b/panda/src/event/asyncFuture_ext.cxx
index 7bc23769137..26c97f90e18 100644
--- a/panda/src/event/asyncFuture_ext.cxx
+++ b/panda/src/event/asyncFuture_ext.cxx
@@ -398,6 +398,10 @@ PyObject *Extension<AsyncFuture>::
 get_cancelled_error_type() {
   static PyObject *exc_type = nullptr;
   if (exc_type == nullptr) {
+    // This method should not affect the current exception, so stash it.
+    PyObject *curexc_type, *curexc_value, *curexc_traceback;
+    PyErr_Fetch(&curexc_type, &curexc_value, &curexc_traceback);
+
     // Get the CancelledError that asyncio uses, too.
 #if PY_VERSION_HEX >= 0x03080000
     PyObject *module = PyImport_ImportModule("asyncio.exceptions");
@@ -408,9 +412,6 @@ get_cancelled_error_type() {
       exc_type = PyObject_GetAttrString(module, "CancelledError");
       Py_DECREF(module);
     }
-    else {
-      PyErr_Clear();
-    }
 
     // If we can't get that, we should pretend and make our own.
     if (exc_type == nullptr) {
@@ -424,6 +425,8 @@ get_cancelled_error_type() {
                                             nullptr, nullptr);
 #endif
     }
+
+    PyErr_Restore(curexc_type, curexc_value, curexc_traceback);
   }
   return exc_type;
 }