bpo-31556: asyncio.wait_for can cancel futures faster with timeout <= 0 (#3703)

1 files changed, 9 insertions, 0 deletions

diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 575d205..52fef18 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -334,6 +334,15 @@ def wait_for(fut, timeout, *, loop=None):
     if timeout is None:
         return (yield from fut)
 
+    if timeout <= 0:
+        fut = ensure_future(fut, loop=loop)
+
+        if fut.done():
+            return fut.result()
+
+        fut.cancel()
+        raise futures.TimeoutError()
+
     waiter = loop.create_future()
     timeout_handle = loop.call_later(timeout, _release_waiter, waiter)
     cb = functools.partial(_release_waiter, waiter)