gh-130145: fix loop.run_forever when loop is already running (#130146)

Author: kumaraditya303

Lib/asyncio/base_events.py

@@ -671,8 +671,8 @@ def _run_forever_cleanup(self):
 
  def run_forever(self):
  """Run until stop() is called."""
+ self._run_forever_setup()
  try:
- self._run_forever_setup()
  while True:
  self._run_once()
  if self._stopping:

Lib/test/test_asyncio/test_events.py

@@ -3004,6 +3004,22 @@ async def main():
  self.loop.run_until_complete(main()),
  'hello')
 
+ def test_get_running_loop_already_running(self):
+ async def main():
+ running_loop = asyncio.get_running_loop()
+ loop = asyncio.new_event_loop()
+ try:
+ loop.run_forever()
+ except RuntimeError:
+ pass
+ else:
+ self.fail("RuntimeError not raised")
+
+ self.assertIs(asyncio.get_running_loop(), running_loop)
+
+ self.loop.run_until_complete(main())
+
+
  def test_get_event_loop_returns_running_loop(self):
  class TestError(Exception):
  pass

Misc/NEWS.d/next/Library/2025-02-15-07-50-37.gh-issue-130145.I0CkV0.rst

@@ -0,0 +1 @@
+Fix :meth:`!asyncio.AbstractEventloop.run_forever` when another loop is already running.