[Python-checkins] bpo-41696: Fix handling of debug mode in asyncio.run (GH-22069) (#22072)

Miss Islington (bot) webhook-mailer at python.org
Thu Sep 3 16:54:16 EDT 2020

commit: 1f5f12737755f246fee83a54c600779ad76934a4
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-09-03T13:54:06-07:00

bpo-41696: Fix handling of debug mode in asyncio.run (GH-22069) (#22072)

* bpo-41696: Fix handling of debug mode in asyncio.run

This allows PYTHONASYNCIODEBUG or -X dev to enable asyncio debug mode
when using asyncio.run

* 📜🤖 Added by blurb_it.

Co-authored-by: hauntsaninja <>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
(cherry picked from commit 0770ad948cb6d9f7f6c4002efd83e27c27069808)

Co-authored-by: Shantanu <12621235+hauntsaninja at users.noreply.github.com>

Co-authored-by: Shantanu <12621235+hauntsaninja at users.noreply.github.com>

A Misc/NEWS.d/next/Library/2020-09-03-01-35-32.bpo-41696.zkYGre.rst
M Lib/asyncio/runners.py
M Lib/test/test_asyncio/test_runners.py

diff --git a/Lib/asyncio/runners.py b/Lib/asyncio/runners.py
index 2e37e18b45fc1..d2fa8b7f13861 100644
--- a/Lib/asyncio/runners.py
+++ b/Lib/asyncio/runners.py
@@ -5,7 +5,7 @@
 from . import tasks
-def run(main, *, debug=False):
+def run(main, *, debug=None):
     """Execute the coroutine and return the result.
     This function runs the passed coroutine, taking care of
@@ -39,7 +39,8 @@ async def main():
     loop = events.new_event_loop()
-        loop.set_debug(debug)
+        if debug is not None:
+            loop.set_debug(debug)
         return loop.run_until_complete(main)
diff --git a/Lib/test/test_asyncio/test_runners.py b/Lib/test/test_asyncio/test_runners.py
index 3b58ddee443ad..b9ae02dc3c04e 100644
--- a/Lib/test/test_asyncio/test_runners.py
+++ b/Lib/test/test_asyncio/test_runners.py
@@ -87,6 +87,9 @@ async def main(expected):
         asyncio.run(main(True), debug=True)
+        with mock.patch('asyncio.coroutines._is_debug_mode', lambda: True):
+            asyncio.run(main(True))
+            asyncio.run(main(False), debug=False)
     def test_asyncio_run_from_running_loop(self):
         async def main():
diff --git a/Misc/NEWS.d/next/Library/2020-09-03-01-35-32.bpo-41696.zkYGre.rst b/Misc/NEWS.d/next/Library/2020-09-03-01-35-32.bpo-41696.zkYGre.rst
new file mode 100644
index 0000000000000..67bbbb857f18c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-03-01-35-32.bpo-41696.zkYGre.rst
@@ -0,0 +1 @@
+Fix handling of debug mode in :func:`asyncio.run`. This allows setting ``PYTHONASYNCIODEBUG`` or ``-X dev`` to enable asyncio debug mode when using :func:`asyncio.run`.
\ No newline at end of file

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