python · 1st1 · Sep 3, 2020 · Sep 3, 2020 · Sep 3, 2020
diff --git 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()
    try:
        events.set_event_loop(loop)
-        loop.set_debug(debug)
+        if debug is not None:
+            loop.set_debug(debug)
        return loop.run_until_complete(main)
    finally:
        try:

diff --git 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(False))
        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
@@ -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`.
Original file line number	Diff line number	Diff line change
		@@ -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`.