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: [PATCH] Fix stacktraces when using ObservableDeferred and async/await
(#6836)
---
changelog.d/6836.misc | 1 +
synapse/util/async_helpers.py | 4 ++++
2 files changed, 5 insertions(+)
create mode 100644 changelog.d/6836.misc
diff --git a/changelog.d/6836.misc b/changelog.d/6836.misc
new file mode 100644
index 0000000000..232488e1e5
--- /dev/null
+++ b/changelog.d/6836.misc
@@ -0,0 +1 @@
+Fix stacktraces when using `ObservableDeferred` and async/await.
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)
--
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