bpo-35125: remove inner callback on outer cancellation in asyncio shield (GH-10340)
When the future returned by shield is cancelled, its completion callback of the
inner future is not removed. This makes the callback list of inner inner future
grow each time a shield is created and cancelled.
This change unregisters the callback from the inner future when the outer
future is cancelled.
https://bugs.python.org/issue35125
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index b007b74..211b912 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -818,7 +818,7 @@
loop = futures._get_loop(inner)
outer = loop.create_future()
- def _done_callback(inner):
+ def _inner_done_callback(inner):
if outer.cancelled():
if not inner.cancelled():
# Mark inner's result as retrieved.
@@ -834,7 +834,13 @@
else:
outer.set_result(inner.result())
- inner.add_done_callback(_done_callback)
+
+ def _outer_done_callback(outer):
+ if not inner.done():
+ inner.remove_done_callback(_inner_done_callback)
+
+ inner.add_done_callback(_inner_done_callback)
+ outer.add_done_callback(_outer_done_callback)
return outer
diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py
index c4f6d70..fa9783f 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -1777,7 +1777,7 @@
test_utils.run_briefly(self.loop)
self.assertIs(outer.exception(), exc)
- def test_shield_cancel(self):
+ def test_shield_cancel_inner(self):
inner = self.new_future(self.loop)
outer = asyncio.shield(inner)
test_utils.run_briefly(self.loop)
@@ -1785,6 +1785,15 @@
test_utils.run_briefly(self.loop)
self.assertTrue(outer.cancelled())
+ def test_shield_cancel_outer(self):
+ inner = self.new_future(self.loop)
+ outer = asyncio.shield(inner)
+ test_utils.run_briefly(self.loop)
+ outer.cancel()
+ test_utils.run_briefly(self.loop)
+ self.assertTrue(outer.cancelled())
+ self.assertEqual(0, 0 if outer._callbacks is None else len(outer._callbacks))
+
def test_shield_shortcut(self):
fut = self.new_future(self.loop)
fut.set_result(42)
diff --git a/Misc/NEWS.d/next/Library/2019-02-15-17-18-50.bpo-35125.h0xk0f.rst b/Misc/NEWS.d/next/Library/2019-02-15-17-18-50.bpo-35125.h0xk0f.rst
new file mode 100644
index 0000000..2e28a25
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-02-15-17-18-50.bpo-35125.h0xk0f.rst
@@ -0,0 +1 @@
+Asyncio: Remove inner callback on outer cancellation in shield