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bpo-31709: Drop support for asynchronous __aiter__. (#3903)

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Yury Selivanov 2017-10-06 02:08:57 -04:00 committed by GitHub
parent 86566702f3
commit faa135acbf
9 changed files with 47 additions and 300 deletions
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53
Doc/reference/datamodel.rst
View file

@ -2520,9 +2520,8 @@ generators, coroutines do not directly support iteration.
Asynchronous Iterators
----------------------
An *asynchronous iterable* is able to call asynchronous code in its
``__aiter__`` implementation, and an *asynchronous iterator* can call
asynchronous code in its ``__anext__`` method.
An *asynchronous iterator* can call asynchronous code in
its ``__anext__`` method.
Asynchronous iterators can be used in an :keyword:`async for` statement.
@ -2552,48 +2551,14 @@ An example of an asynchronous iterable object::
.. versionadded:: 3.5
.. note::
.. versionchanged:: 3.7
Prior to Python 3.7, ``__aiter__`` could return an *awaitable*
that would resolve to an
:term:`asynchronous iterator <asynchronous iterator>`.
.. versionchanged:: 3.5.2
Starting with CPython 3.5.2, ``__aiter__`` can directly return
:term:`asynchronous iterators <asynchronous iterator>`. Returning
an :term:`awaitable` object will result in a
:exc:`PendingDeprecationWarning`.
The recommended way of writing backwards compatible code in
CPython 3.5.x is to continue returning awaitables from
``__aiter__``. If you want to avoid the PendingDeprecationWarning
and keep the code backwards compatible, the following decorator
can be used::
import functools
import sys
if sys.version_info < (3, 5, 2):
def aiter_compat(func):
@functools.wraps(func)
async def wrapper(self):
return func(self)
return wrapper
else:
def aiter_compat(func):
return func
Example::
class AsyncIterator:
@aiter_compat
def __aiter__(self):
return self
async def __anext__(self):
...
Starting with CPython 3.6, the :exc:`PendingDeprecationWarning`
will be replaced with the :exc:`DeprecationWarning`.
In CPython 3.7, returning an awaitable from ``__aiter__`` will
result in a :exc:`RuntimeError`.
Starting with Python 3.7, ``__aiter__`` must return an
asynchronous iterator object. Returning anything else
will result in a :exc:`TypeError` error.
.. _async-context-managers:

1
Include/genobject.h
View file

@ -56,7 +56,6 @@ PyAPI_DATA(PyTypeObject) PyCoro_Type;
PyAPI_DATA(PyTypeObject) _PyCoroWrapper_Type;
PyAPI_DATA(PyTypeObject) _PyAIterWrapper_Type;
PyObject *_PyAIterWrapper_New(PyObject *aiter);
#define PyCoro_CheckExact(op) (Py_TYPE(op) == &PyCoro_Type)
PyObject *_PyCoro_GetAwaitableIter(PyObject *o);

24
Lib/asyncio/streams.py
View file

@ -676,20 +676,12 @@ def readexactly(self, n):
self._maybe_resume_transport()
return data
if compat.PY35:
@coroutine
def __aiter__(self):
return self
def __aiter__(self):
return self
@coroutine
def __anext__(self):
val = yield from self.readline()
if val == b'':
raise StopAsyncIteration
return val
if compat.PY352:
# In Python 3.5.2 and greater, __aiter__ should return
# the asynchronous iterator directly.
def __aiter__(self):
return self
@coroutine
def __anext__(self):
val = yield from self.readline()
if val == b'':
raise StopAsyncIteration
return val

4
Lib/test/test_collections.py
View file

@ -660,7 +660,7 @@ def __hash__(self):
def test_AsyncIterable(self):
class AI:
async def __aiter__(self):
def __aiter__(self):
return self
self.assertTrue(isinstance(AI(), AsyncIterable))
self.assertTrue(issubclass(AI, AsyncIterable))
@ -674,7 +674,7 @@ async def __aiter__(self):
def test_AsyncIterator(self):
class AI:
async def __aiter__(self):
def __aiter__(self):
return self
async def __anext__(self):
raise StopAsyncIteration

110
Lib/test/test_coroutines.py
View file

@ -1382,7 +1382,7 @@ class AsyncIter:
def __init__(self):
self.i = 0
async def __aiter__(self):
def __aiter__(self):
nonlocal aiter_calls
aiter_calls += 1
return self
@ -1401,9 +1401,8 @@ async def __anext__(self):
buffer = []
async def test1():
with self.assertWarnsRegex(DeprecationWarning, "legacy"):
async for i1, i2 in AsyncIter():
buffer.append(i1 + i2)
async for i1, i2 in AsyncIter():
buffer.append(i1 + i2)
yielded, _ = run_async(test1())
# Make sure that __aiter__ was called only once
@ -1415,13 +1414,12 @@ async def test1():
buffer = []
async def test2():
nonlocal buffer
with self.assertWarnsRegex(DeprecationWarning, "legacy"):
async for i in AsyncIter():
buffer.append(i[0])
if i[0] == 20:
break
else:
buffer.append('what?')
async for i in AsyncIter():
buffer.append(i[0])
if i[0] == 20:
break
else:
buffer.append('what?')
buffer.append('end')
yielded, _ = run_async(test2())
@ -1434,13 +1432,12 @@ async def test2():
buffer = []
async def test3():
nonlocal buffer
with self.assertWarnsRegex(DeprecationWarning, "legacy"):
async for i in AsyncIter():
if i[0] > 20:
continue
buffer.append(i[0])
else:
buffer.append('what?')
async for i in AsyncIter():
if i[0] > 20:
continue
buffer.append(i[0])
else:
buffer.append('what?')
buffer.append('end')
yielded, _ = run_async(test3())
@ -1479,7 +1476,7 @@ async def foo():
with self.assertRaisesRegex(
TypeError,
r"async for' received an invalid object.*__aiter.*\: I"):
r"that does not implement __anext__"):
run_async(foo())
@ -1508,25 +1505,6 @@ async def foo():
self.assertEqual(sys.getrefcount(aiter), refs_before)
def test_for_5(self):
class I:
async def __aiter__(self):
return self
def __anext__(self):
return 123
async def foo():
with self.assertWarnsRegex(DeprecationWarning, "legacy"):
async for i in I():
print('never going to happen')
with self.assertRaisesRegex(
TypeError,
"async for' received an invalid object.*__anext.*int"):
run_async(foo())
def test_for_6(self):
I = 0
@ -1622,13 +1600,12 @@ async def main():
def test_for_7(self):
CNT = 0
class AI:
async def __aiter__(self):
def __aiter__(self):
1/0
async def foo():
nonlocal CNT
with self.assertWarnsRegex(DeprecationWarning, "legacy"):
async for i in AI():
CNT += 1
async for i in AI():
CNT += 1
CNT += 10
with self.assertRaises(ZeroDivisionError):
run_async(foo())
@ -1652,37 +1629,6 @@ async def foo():
run_async(foo())
self.assertEqual(CNT, 0)
def test_for_9(self):
# Test that DeprecationWarning can safely be converted into
# an exception (__aiter__ should not have a chance to raise
# a ZeroDivisionError.)
class AI:
async def __aiter__(self):
1/0
async def foo():
async for i in AI():
pass
with self.assertRaises(DeprecationWarning):
with warnings.catch_warnings():
warnings.simplefilter("error")
run_async(foo())
def test_for_10(self):
# Test that DeprecationWarning can safely be converted into
# an exception.
class AI:
async def __aiter__(self):
pass
async def foo():
async for i in AI():
pass
with self.assertRaises(DeprecationWarning):
with warnings.catch_warnings():
warnings.simplefilter("error")
run_async(foo())
def test_for_11(self):
class F:
def __aiter__(self):
@ -1703,24 +1649,6 @@ async def main():
err = c.exception
self.assertIsInstance(err.__cause__, ZeroDivisionError)
def test_for_12(self):
class F:
def __aiter__(self):
return self
def __await__(self):
1 / 0
async def main():
async for _ in F():
pass
with self.assertRaisesRegex(TypeError,
'an invalid object from __aiter__') as c:
main().send(None)
err = c.exception
self.assertIsInstance(err.__cause__, ZeroDivisionError)
def test_for_tuple(self):
class Done(Exception): pass

1
Misc/NEWS.d/next/Core and Builtins/2017-10-06-00-27-04.bpo-31709._PmU51.rst Normal file
View file

@ -0,0 +1 @@
Drop support of asynchronous __aiter__.

94
Objects/genobject.c
View file

@ -1141,100 +1141,6 @@ PyCoro_New(PyFrameObject *f, PyObject *name, PyObject *qualname)
}
/* __aiter__ wrapper; see http://bugs.python.org/issue27243 for details. */
typedef struct {
PyObject_HEAD
PyObject *ags_aiter;
} PyAIterWrapper;
static PyObject *
aiter_wrapper_iternext(PyAIterWrapper *aw)
{
_PyGen_SetStopIterationValue(aw->ags_aiter);
return NULL;
}
static int
aiter_wrapper_traverse(PyAIterWrapper *aw, visitproc visit, void *arg)
{
Py_VISIT((PyObject *)aw->ags_aiter);
return 0;
}
static void
aiter_wrapper_dealloc(PyAIterWrapper *aw)
{
_PyObject_GC_UNTRACK((PyObject *)aw);
Py_CLEAR(aw->ags_aiter);
PyObject_GC_Del(aw);
}
static PyAsyncMethods aiter_wrapper_as_async = {
PyObject_SelfIter, /* am_await */
0, /* am_aiter */
0 /* am_anext */
};
PyTypeObject _PyAIterWrapper_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"aiter_wrapper",
sizeof(PyAIterWrapper), /* tp_basicsize */
0, /* tp_itemsize */
(destructor)aiter_wrapper_dealloc, /* destructor tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
&aiter_wrapper_as_async, /* tp_as_async */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
"A wrapper object for __aiter__ bakwards compatibility.",
(traverseproc)aiter_wrapper_traverse, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
PyObject_SelfIter, /* tp_iter */
(iternextfunc)aiter_wrapper_iternext, /* tp_iternext */
0, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
};
PyObject *
_PyAIterWrapper_New(PyObject *aiter)
{
PyAIterWrapper *aw = PyObject_GC_New(PyAIterWrapper,
&_PyAIterWrapper_Type);
if (aw == NULL) {
return NULL;
}
Py_INCREF(aiter);
aw->ags_aiter = aiter;
_PyObject_GC_TRACK(aw);
return (PyObject *)aw;
}
/* ========= Asynchronous Generators ========= */

54
Python/ceval.c
View file

@ -1708,7 +1708,6 @@ _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
TARGET(GET_AITER) {
unaryfunc getter = NULL;
PyObject *iter = NULL;
PyObject *awaitable = NULL;
PyObject *obj = TOP();
PyTypeObject *type = Py_TYPE(obj);
@ -1735,57 +1734,20 @@ _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
goto error;
}
if (Py_TYPE(iter)->tp_as_async != NULL &&
Py_TYPE(iter)->tp_as_async->am_anext != NULL) {
/* Starting with CPython 3.5.2 __aiter__ should return
asynchronous iterators directly (not awaitables that
resolve to asynchronous iterators.)
Therefore, we check if the object that was returned
from __aiter__ has an __anext__ method. If it does,
we wrap it in an awaitable that resolves to `iter`.
See http://bugs.python.org/issue27243 for more
details.
*/
PyObject *wrapper = _PyAIterWrapper_New(iter);
Py_DECREF(iter);
SET_TOP(wrapper);
DISPATCH();
}
awaitable = _PyCoro_GetAwaitableIter(iter);
if (awaitable == NULL) {
_PyErr_FormatFromCause(
PyExc_TypeError,
"'async for' received an invalid object "
"from __aiter__: %.100s",
Py_TYPE(iter)->tp_name);
if (Py_TYPE(iter)->tp_as_async == NULL ||
Py_TYPE(iter)->tp_as_async->am_anext == NULL) {
SET_TOP(NULL);
PyErr_Format(
PyExc_TypeError,
"'async for' received an object from __aiter__ "
"that does not implement __anext__: %.100s",
Py_TYPE(iter)->tp_name);
Py_DECREF(iter);
goto error;
} else {
Py_DECREF(iter);
if (PyErr_WarnFormat(
PyExc_DeprecationWarning, 1,
"'%.100s' implements legacy __aiter__ protocol; "
"__aiter__ should return an asynchronous "
"iterator, not awaitable",
type->tp_name))
{
/* Warning was converted to an error. */
Py_DECREF(awaitable);
SET_TOP(NULL);
goto error;
}
}
SET_TOP(awaitable);
PREDICT(LOAD_CONST);
SET_TOP(iter);
DISPATCH();
}

6
Python/compile.c
View file

@ -2298,8 +2298,6 @@ compiler_async_for(struct compiler *c, stmt_ty s)
VISIT(c, expr, s->v.AsyncFor.iter);
ADDOP(c, GET_AITER);
ADDOP_O(c, LOAD_CONST, Py_None, consts);
ADDOP(c, YIELD_FROM);
compiler_use_next_block(c, try);
@ -3867,8 +3865,6 @@ compiler_async_comprehension_generator(struct compiler *c,
/* Sub-iter - calculate on the fly */
VISIT(c, expr, gen->iter);
ADDOP(c, GET_AITER);
ADDOP_O(c, LOAD_CONST, Py_None, consts);
ADDOP(c, YIELD_FROM);
}
compiler_use_next_block(c, try);
@ -4033,8 +4029,6 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
if (outermost->is_async) {
ADDOP(c, GET_AITER);
ADDOP_O(c, LOAD_CONST, Py_None, consts);
ADDOP(c, YIELD_FROM);
} else {
ADDOP(c, GET_ITER);
}