https://github.com/python/cpython/commit/2c42e13e80610a9dedcb15b57d142602e8143481
commit: 2c42e13e80610a9dedcb15b57d142602e8143481
branch: main
author: Mark Shannon <[email protected]>
committer: markshannon <[email protected]>
date: 2024-07-26T14:37:35+01:00
summary:
GH-116090: Fix test and clarify behavior for exception events when exhausting a
generator. (GH-120697)
files:
M Doc/library/sys.monitoring.rst
M Lib/test/test_monitoring.py
diff --git a/Doc/library/sys.monitoring.rst b/Doc/library/sys.monitoring.rst
index 0fa06da522049f..3ead20815fa30e 100644
--- a/Doc/library/sys.monitoring.rst
+++ b/Doc/library/sys.monitoring.rst
@@ -226,6 +226,10 @@ To allow tools to monitor for real exceptions without
slowing down generators
and coroutines, the :monitoring-event:`STOP_ITERATION` event is provided.
:monitoring-event:`STOP_ITERATION` can be locally disabled, unlike
:monitoring-event:`RAISE`.
+Note that the :monitoring-event:`STOP_ITERATION` event and the
:monitoring-event:`RAISE`
+event for a :exc:`StopIteration` exception are equivalent, and are treated as
interchangeable
+when generating events. Implementations will favor
:monitoring-event:`STOP_ITERATION` for
+performance reasons, but may generate a :monitoring-event:`RAISE` event with a
:exc:`StopIteration`.
Turning events on and off
-------------------------
diff --git a/Lib/test/test_monitoring.py b/Lib/test/test_monitoring.py
index 1a129b9432e72d..d7043cd4866a1c 100644
--- a/Lib/test/test_monitoring.py
+++ b/Lib/test/test_monitoring.py
@@ -832,20 +832,43 @@ def func1():
self.check_events(func1, [("raise", KeyError)])
- # gh-116090: This test doesn't really require specialization, but running
- # it without specialization exposes a monitoring bug.
- @requires_specialization
def test_implicit_stop_iteration(self):
+ """Generators are documented as raising a StopIteration
+ when they terminate.
+ However, we don't do that if we can avoid it, for speed.
+ sys.monitoring handles that by injecting a STOP_ITERATION
+ event when we would otherwise have skip the RAISE event.
+ This test checks that both paths record an equivalent event.
+ """
def gen():
yield 1
return 2
- def implicit_stop_iteration():
- for _ in gen():
+ def implicit_stop_iteration(iterator=None):
+ if iterator is None:
+ iterator = gen()
+ for _ in iterator:
pass
- self.check_events(implicit_stop_iteration, [("raise", StopIteration)],
recorders=(StopiterationRecorder,))
+ recorders=(ExceptionRecorder, StopiterationRecorder,)
+ expected = [("raise", StopIteration)]
+
+ # Make sure that the loop is unspecialized, and that it will not
+ # re-specialize immediately, so that we can we can test the
+ # unspecialized version of the loop first.
+ # Note: this assumes that we don't specialize loops over sets.
+ implicit_stop_iteration(set(range(100)))
+
+ # This will record a RAISE event for the StopIteration.
+ self.check_events(implicit_stop_iteration, expected,
recorders=recorders)
+
+ # Now specialize, so that we see a STOP_ITERATION event.
+ for _ in range(100):
+ implicit_stop_iteration()
+
+ # This will record a STOP_ITERATION event for the StopIteration.
+ self.check_events(implicit_stop_iteration, expected,
recorders=recorders)
initial = [
("raise", ZeroDivisionError),
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