[3.8] bpo-39191: Don't spawn a task before failing (GH-17796) (GH-17820)
(cherry picked from commit 3a5de511596f17575de082dcb8d43d63b2bd2da9)
Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index bfd4011..aedf0c5 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -547,14 +547,17 @@
'asyncgen': agen
})
- def run_forever(self):
- """Run until stop() is called."""
- self._check_closed()
+ def _check_runnung(self):
if self.is_running():
raise RuntimeError('This event loop is already running')
if events._get_running_loop() is not None:
raise RuntimeError(
'Cannot run the event loop while another loop is running')
+
+ def run_forever(self):
+ """Run until stop() is called."""
+ self._check_closed()
+ self._check_runnung()
self._set_coroutine_origin_tracking(self._debug)
self._thread_id = threading.get_ident()
@@ -586,6 +589,7 @@
Return the Future's result, or raise its exception.
"""
self._check_closed()
+ self._check_runnung()
new_task = not futures.isfuture(future)
future = tasks.ensure_future(future, loop=self)
diff --git a/Misc/NEWS.d/next/Library/2020-01-02-17-28-03.bpo-39191.ur_scy.rst b/Misc/NEWS.d/next/Library/2020-01-02-17-28-03.bpo-39191.ur_scy.rst
new file mode 100644
index 0000000..138c93c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-01-02-17-28-03.bpo-39191.ur_scy.rst
@@ -0,0 +1,3 @@
+Perform a check for running loop before starting a new task in
+``loop.run_until_complete()`` to fail fast; it prevents the side effect of
+new task spawning before exception raising.