From ae5b3104f0023171b2bb89f08a066e5974ee7666 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Mon, 3 Feb 2020 17:10:54 +0000
Subject: Fix stacktraces when using ObservableDeferred and async/await (#6836)

---
 synapse/util/async_helpers.py | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'synapse/util/async_helpers.py')

diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 04b6abdc24..581dffd8a0 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -73,6 +73,10 @@ class ObservableDeferred(object):
         def errback(f):
             object.__setattr__(self, "_result", (False, f))
             while self._observers:
+                # This is a little bit of magic to correctly propagate stack
+                # traces when we `await` on one of the observer deferreds.
+                f.value.__failure__ = f
+
                 try:
                     # TODO: Handle errors here.
                     self._observers.pop().errback(f)
-- 
cgit 1.5.1