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gh-112182: Replace StopIteration with RuntimeError for future (#113220)
When an `StopIteration` raises into `asyncio.Future`, this will cause a thread to hang. This commit address this by not raising an exception and silently transforming the `StopIteration` with a `RuntimeError`, which the caller can reconstruct from `fut.exception().__cause__`
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@ -269,9 +269,13 @@ def set_exception(self, exception):
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raise exceptions.InvalidStateError(f'{self._state}: {self!r}')
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if isinstance(exception, type):
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exception = exception()
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if type(exception) is StopIteration:
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raise TypeError("StopIteration interacts badly with generators "
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"and cannot be raised into a Future")
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if isinstance(exception, StopIteration):
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new_exc = RuntimeError("StopIteration interacts badly with "
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"generators and cannot be raised into a "
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"Future")
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new_exc.__cause__ = exception
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new_exc.__context__ = exception
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exception = new_exc
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self._exception = exception
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self._exception_tb = exception.__traceback__
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self._state = _FINISHED
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@ -270,10 +270,6 @@ def test_exception(self):
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f = self._new_future(loop=self.loop)
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self.assertRaises(asyncio.InvalidStateError, f.exception)
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# StopIteration cannot be raised into a Future - CPython issue26221
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self.assertRaisesRegex(TypeError, "StopIteration .* cannot be raised",
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f.set_exception, StopIteration)
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f.set_exception(exc)
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self.assertFalse(f.cancelled())
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self.assertTrue(f.done())
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@ -283,6 +279,25 @@ def test_exception(self):
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self.assertRaises(asyncio.InvalidStateError, f.set_exception, None)
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self.assertFalse(f.cancel())
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def test_stop_iteration_exception(self, stop_iteration_class=StopIteration):
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exc = stop_iteration_class()
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f = self._new_future(loop=self.loop)
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f.set_exception(exc)
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self.assertFalse(f.cancelled())
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self.assertTrue(f.done())
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self.assertRaises(RuntimeError, f.result)
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exc = f.exception()
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cause = exc.__cause__
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self.assertIsInstance(exc, RuntimeError)
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self.assertRegex(str(exc), 'StopIteration .* cannot be raised')
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self.assertIsInstance(cause, stop_iteration_class)
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def test_stop_iteration_subclass_exception(self):
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class MyStopIteration(StopIteration):
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pass
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self.test_stop_iteration_exception(MyStopIteration)
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def test_exception_class(self):
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f = self._new_future(loop=self.loop)
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f.set_exception(RuntimeError)
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@ -0,0 +1,3 @@
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:meth:`asyncio.futures.Future.set_exception()` now transforms :exc:`StopIteration`
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into :exc:`RuntimeError` instead of hanging or other misbehavior. Patch
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contributed by Jamie Phan.
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@ -597,13 +597,28 @@ future_set_exception(asyncio_state *state, FutureObj *fut, PyObject *exc)
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PyErr_SetString(PyExc_TypeError, "invalid exception object");
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return NULL;
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}
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if (Py_IS_TYPE(exc_val, (PyTypeObject *)PyExc_StopIteration)) {
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if (PyErr_GivenExceptionMatches(exc_val, PyExc_StopIteration)) {
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const char *msg = "StopIteration interacts badly with "
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"generators and cannot be raised into a "
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"Future";
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PyObject *message = PyUnicode_FromString(msg);
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if (message == NULL) {
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Py_DECREF(exc_val);
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PyErr_SetString(PyExc_TypeError,
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"StopIteration interacts badly with generators "
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"and cannot be raised into a Future");
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return NULL;
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}
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PyObject *err = PyObject_CallOneArg(PyExc_RuntimeError, message);
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Py_DECREF(message);
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if (err == NULL) {
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Py_DECREF(exc_val);
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return NULL;
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}
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assert(PyExceptionInstance_Check(err));
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PyException_SetCause(err, Py_NewRef(exc_val));
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PyException_SetContext(err, Py_NewRef(exc_val));
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Py_DECREF(exc_val);
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exc_val = err;
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}
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assert(!fut->fut_exception);
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assert(!fut->fut_exception_tb);
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