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bpo-32670: Enforce PEP 479. (#5327)

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Yury Selivanov 2018-01-26 15:24:24 -05:00 committed by GitHub
parent dba976b8a2
commit 43c47fe096
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7 changed files with 38 additions and 80 deletions
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14
Doc/library/exceptions.rst
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@ -367,17 +367,21 @@ The following exceptions are the exceptions that are usually raised.
raised, and the value returned by the function is used as the
:attr:`value` parameter to the constructor of the exception.
If a generator function defined in the presence of a ``from __future__
import generator_stop`` directive raises :exc:`StopIteration`, it will be
converted into a :exc:`RuntimeError` (retaining the :exc:`StopIteration`
as the new exception's cause).
If a generator code directly or indirectly raises :exc:`StopIteration`,
it is converted into a :exc:`RuntimeError` (retaining the
:exc:`StopIteration` as the new exception's cause).
.. versionchanged:: 3.3
Added ``value`` attribute and the ability for generator functions to
use it to return a value.
.. versionchanged:: 3.5
Introduced the RuntimeError transformation.
Introduced the RuntimeError transformation via
``from __future__ import generator_stop``, see :pep:`479`.
.. versionchanged:: 3.7
Enable :pep:`479` for all code by default: a :exc:`StopIteration`
error raised in a generator is transformed into a :exc:`RuntimeError`.
.. exception:: StopAsyncIteration

6
Doc/whatsnew/3.7.rst
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@ -935,6 +935,12 @@ that may require changes to your code.
Changes in Python behavior
--------------------------
* :pep:`479` is enabled for all code in Python 3.7, meaning that
:exc:`StopIteration` exceptions raised directly or indirectly in
coroutines and generators are transformed into :exc:`RuntimeError`
exceptions.
(Contributed by Yury Selivanov in :issue:`32670`.)
* Due to an oversight, earlier Python versions erroneously accepted the
following syntax::

22
Lib/test/test_generators.py
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@ -265,26 +265,16 @@ class ExceptionTest(unittest.TestCase):
self.assertEqual(next(g), "done")
self.assertEqual(sys.exc_info(), (None, None, None))
def test_stopiteration_warning(self):
def test_stopiteration_error(self):
# See also PEP 479.
def gen():
raise StopIteration
yield
with self.assertRaises(StopIteration), \
self.assertWarnsRegex(DeprecationWarning, "StopIteration"):
with self.assertRaisesRegex(RuntimeError, 'raised StopIteration'):
next(gen())
with self.assertRaisesRegex(DeprecationWarning,
"generator .* raised StopIteration"), \
warnings.catch_warnings():
warnings.simplefilter('error')
next(gen())
def test_tutorial_stopiteration(self):
# Raise StopIteration" stops the generator too:
@ -296,13 +286,7 @@ class ExceptionTest(unittest.TestCase):
g = f()
self.assertEqual(next(g), 1)
with self.assertWarnsRegex(DeprecationWarning, "StopIteration"):
with self.assertRaises(StopIteration):
next(g)
with self.assertRaises(StopIteration):
# This time StopIteration isn't raised from the generator's body,
# hence no warning.
with self.assertRaisesRegex(RuntimeError, 'raised StopIteration'):
next(g)
def test_return_tuple(self):

11
Lib/test/test_with.py
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@ -458,8 +458,8 @@ class ExceptionalTestCase(ContextmanagerAssertionMixin, unittest.TestCase):
with cm():
raise StopIteration("from with")
with self.assertWarnsRegex(DeprecationWarning, "StopIteration"):
self.assertRaises(StopIteration, shouldThrow)
with self.assertRaisesRegex(StopIteration, 'from with'):
shouldThrow()
def testRaisedStopIteration2(self):
# From bug 1462485
@ -473,7 +473,8 @@ class ExceptionalTestCase(ContextmanagerAssertionMixin, unittest.TestCase):
with cm():
raise StopIteration("from with")
self.assertRaises(StopIteration, shouldThrow)
with self.assertRaisesRegex(StopIteration, 'from with'):
shouldThrow()
def testRaisedStopIteration3(self):
# Another variant where the exception hasn't been instantiated
@ -486,8 +487,8 @@ class ExceptionalTestCase(ContextmanagerAssertionMixin, unittest.TestCase):
with cm():
raise next(iter([]))
with self.assertWarnsRegex(DeprecationWarning, "StopIteration"):
self.assertRaises(StopIteration, shouldThrow)
with self.assertRaises(StopIteration):
shouldThrow()
def testRaisedGeneratorExit1(self):
# From bug 1462485

5
Misc/NEWS.d/next/Core and Builtins/2018-01-25-17-03-46.bpo-32670.YsqJUC.rst Normal file
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@ -0,0 +1,5 @@
Enforce PEP 479 for all code.
This means that manually raising a StopIteration exception from a generator
is prohibited for all code, regardless of whether 'from __future__ import
generator_stop' was used or not.

58
Objects/genobject.c
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@ -248,59 +248,17 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
Py_CLEAR(result);
}
else if (!result && PyErr_ExceptionMatches(PyExc_StopIteration)) {
/* Check for __future__ generator_stop and conditionally turn
* a leaking StopIteration into RuntimeError (with its cause
* set appropriately). */
const int check_stop_iter_error_flags = CO_FUTURE_GENERATOR_STOP |
CO_COROUTINE |
CO_ITERABLE_COROUTINE |
CO_ASYNC_GENERATOR;
if (gen->gi_code != NULL &&
((PyCodeObject *)gen->gi_code)->co_flags &
check_stop_iter_error_flags)
{
/* `gen` is either:
* a generator with CO_FUTURE_GENERATOR_STOP flag;
* a coroutine;
* a generator with CO_ITERABLE_COROUTINE flag
(decorated with types.coroutine decorator);
* an async generator.
*/
const char *msg = "generator raised StopIteration";
if (PyCoro_CheckExact(gen)) {
msg = "coroutine raised StopIteration";
}
else if PyAsyncGen_CheckExact(gen) {
msg = "async generator raised StopIteration";
}
_PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
const char *msg = "generator raised StopIteration";
if (PyCoro_CheckExact(gen)) {
msg = "coroutine raised StopIteration";
}
else {
/* `gen` is an ordinary generator without
CO_FUTURE_GENERATOR_STOP flag.
*/
PyObject *exc, *val, *tb;
/* Pop the exception before issuing a warning. */
PyErr_Fetch(&exc, &val, &tb);
if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
"generator '%.50S' raised StopIteration",
gen->gi_qualname)) {
/* Warning was converted to an error. */
Py_XDECREF(exc);
Py_XDECREF(val);
Py_XDECREF(tb);
}
else {
PyErr_Restore(exc, val, tb);
}
else if PyAsyncGen_CheckExact(gen) {
msg = "async generator raised StopIteration";
}
_PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
}
else if (PyAsyncGen_CheckExact(gen) && !result &&
else if (!result && PyAsyncGen_CheckExact(gen) &&
PyErr_ExceptionMatches(PyExc_StopAsyncIteration))
{
/* code in `gen` raised a StopAsyncIteration error:

2
Python/future.c
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@ -41,7 +41,7 @@ future_check_features(PyFutureFeatures *ff, stmt_ty s, PyObject *filename)
} else if (strcmp(feature, FUTURE_BARRY_AS_BDFL) == 0) {
ff->ff_features |= CO_FUTURE_BARRY_AS_BDFL;
} else if (strcmp(feature, FUTURE_GENERATOR_STOP) == 0) {
ff->ff_features |= CO_FUTURE_GENERATOR_STOP;
continue;
} else if (strcmp(feature, FUTURE_ANNOTATIONS) == 0) {
ff->ff_features |= CO_FUTURE_ANNOTATIONS;
} else if (strcmp(feature, "braces") == 0) {