bpo-37703: improve asyncio.gather documentation regarding cancellation (GH-15312)
These changes updates the doc to comprehensively mention the behaviour of gather.cancel()
Automerge-Triggered-By: @asvetlov
diff --git a/Doc/library/asyncio-task.rst b/Doc/library/asyncio-task.rst
index bac99b7..99f0125 100644
--- a/Doc/library/asyncio-task.rst
+++ b/Doc/library/asyncio-task.rst
@@ -387,6 +387,14 @@
# Task C: Compute factorial(4)...
# Task C: factorial(4) = 24
+ .. note::
+ If *return_exceptions* is False, cancelling gather() after it
+ has been marked done won't cancel any submitted awaitables.
+ For instance, gather can be marked done after propagating an
+ exception to the caller, therefore, calling ``gather.cancel()``
+ after catching an exception (raised by one of the awaitables) from
+ gather won't cancel any other awaitables.
+
.. versionchanged:: 3.7
If the *gather* itself is cancelled, the cancellation is
propagated regardless of *return_exceptions*.