[Python-checkins] bpo-33110: Catch errors raised when running add_done_callback on already completed futures (GH-13141)
Antoine Pitrou
webhook-mailer at python.org
Wed May 22 17:29:06 EDT 2019
https://github.com/python/cpython/commit/2a3a2ece502c05ea33c95dd0db497189e0354bfd
commit: 2a3a2ece502c05ea33c95dd0db497189e0354bfd
branch: master
author: Sam Martin <ABitMoreDepth at users.noreply.github.com>
committer: Antoine Pitrou <antoine at python.org>
date: 2019-05-22T23:29:02+02:00
summary:
bpo-33110: Catch errors raised when running add_done_callback on already completed futures (GH-13141)
Wrap the callback call within the `add_done_callback` function within concurrent.futures, in order to behave in an identical manner to callbacks added to a running future are triggered once it has completed.
files:
A Misc/NEWS.d/next/Library/2019-05-06-22-34-47.bpo-33110.rSJSCh.rst
M Lib/concurrent/futures/_base.py
M Lib/test/test_concurrent_futures.py
diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py
index 8f155f0ea82b..6001e3bdb81b 100644
--- a/Lib/concurrent/futures/_base.py
+++ b/Lib/concurrent/futures/_base.py
@@ -404,7 +404,10 @@ def add_done_callback(self, fn):
if self._state not in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]:
self._done_callbacks.append(fn)
return
- fn(self)
+ try:
+ fn(self)
+ except Exception:
+ LOGGER.exception('exception calling callback for %r', self)
def result(self, timeout=None):
"""Return the result of the call that the future represents.
diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py
index 3c963dff1db2..212ccd8d5320 100644
--- a/Lib/test/test_concurrent_futures.py
+++ b/Lib/test/test_concurrent_futures.py
@@ -1087,6 +1087,22 @@ def fn(callback_future):
f.add_done_callback(fn)
self.assertTrue(was_cancelled)
+ def test_done_callback_raises_already_succeeded(self):
+ with test.support.captured_stderr() as stderr:
+ def raising_fn(callback_future):
+ raise Exception('doh!')
+
+ f = Future()
+
+ # Set the result first to simulate a future that runs instantly,
+ # effectively allowing the callback to be run immediately.
+ f.set_result(5)
+ f.add_done_callback(raising_fn)
+
+ self.assertIn('exception calling callback for', stderr.getvalue())
+ self.assertIn('doh!', stderr.getvalue())
+
+
def test_repr(self):
self.assertRegex(repr(PENDING_FUTURE),
'<Future at 0x[0-9a-f]+ state=pending>')
diff --git a/Misc/NEWS.d/next/Library/2019-05-06-22-34-47.bpo-33110.rSJSCh.rst b/Misc/NEWS.d/next/Library/2019-05-06-22-34-47.bpo-33110.rSJSCh.rst
new file mode 100644
index 000000000000..f1e2460c4927
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-06-22-34-47.bpo-33110.rSJSCh.rst
@@ -0,0 +1 @@
+Handle exceptions raised by functions added by concurrent.futures add_done_callback correctly when the Future has already completed.
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