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bpo-33346: Allow async comprehensions inside implicit async comprehensions (GH-6766) 

Co-authored-by: Pablo Galindo <pablogsal@gmail.com>
This commit is contained in:
Serhiy Storchaka 2021-07-14 00:27:50 +03:00 committed by GitHub
parent 0ee0a740e1
commit 054e9c84ac
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 109 additions and 17 deletions
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11
Doc/reference/expressions.rst
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@ -218,9 +218,9 @@ A comprehension in an :keyword:`!async def` function may consist of either a
:keyword:`!for` or :keyword:`!async for` clause following the leading
expression, may contain additional :keyword:`!for` or :keyword:`!async for`
clauses, and may also use :keyword:`await` expressions.
If a comprehension contains either :keyword:`!async for` clauses
or :keyword:`!await` expressions it is called an
:dfn:`asynchronous comprehension`. An asynchronous comprehension may
If a comprehension contains either :keyword:`!async for` clauses or
:keyword:`!await` expressions or other asynchronous comprehensions it is called
an :dfn:`asynchronous comprehension`. An asynchronous comprehension may
suspend the execution of the coroutine function in which it appears.
See also :pep:`530`.
@ -230,6 +230,11 @@ See also :pep:`530`.
.. versionchanged:: 3.8
``yield`` and ``yield from`` prohibited in the implicitly nested scope.
.. versionchanged:: 3.11
Asynchronous comprehensions are now allowed inside comprehensions in
asynchronous functions. Outer comprehensions implicitly become
asynchronous.
.. _lists:

17
Doc/whatsnew/3.11.rst
View File

@ -148,16 +148,19 @@ See :pep:`657` for more details. (Contributed by Pablo Galindo, Batuhan Taskaya
and Ammar Askar in :issue:`43950`.)
Other Language Changes
======================
A :exc:`TypeError` is now raised instead of an :exc:`AttributeError` in
:meth:`contextlib.ExitStack.enter_context` and
:meth:`contextlib.AsyncExitStack.enter_async_context` for objects which do not
support the :term:`context manager` or :term:`asynchronous context manager`
protocols correspondingly.
(Contributed by Serhiy Storchaka in :issue:`44471`.)
* Asynchronous comprehensions are now allowed inside comprehensions in
asynchronous functions. Outer comprehensions implicitly become
asynchronous. (Contributed by Serhiy Storchaka in :issue:`33346`.)
* A :exc:`TypeError` is now raised instead of an :exc:`AttributeError` in
:meth:`contextlib.ExitStack.enter_context` and
:meth:`contextlib.AsyncExitStack.enter_async_context` for objects which do not
support the :term:`context manager` or :term:`asynchronous context manager`
protocols correspondingly.
(Contributed by Serhiy Storchaka in :issue:`44471`.)
* A :exc:`TypeError` is now raised instead of an :exc:`AttributeError` in
:keyword:`with` and :keyword:`async with` statements for objects which do not

72
Lib/test/test_coroutines.py
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@ -28,6 +28,12 @@ class AsyncYield:
yield self.value
async def asynciter(iterable):
"""Convert an iterable to an asynchronous iterator."""
for x in iterable:
yield x
def run_async(coro):
assert coro.__class__ in {types.GeneratorType, types.CoroutineType}
@ -125,6 +131,11 @@ class AsyncBadSyntaxTest(unittest.TestCase):
for c in b]
""",
"""async def foo():
def bar():
[[async for i in b] for b in els]
""",
"""async def foo():
def bar():
[i for i in els
@ -200,6 +211,13 @@ class AsyncBadSyntaxTest(unittest.TestCase):
[i for i in els if await i]
""",
"""def bar():
[[i async for i in a] for a in elts]
""",
"""[[i async for i in a] for a in elts]
""",
"""async def foo():
await
""",
@ -2011,6 +2029,60 @@ class CoroutineTest(unittest.TestCase):
run_async(f()),
([], {1: 1, 2: 2, 3: 3}))
def test_nested_comp(self):
async def run_list_inside_list():
return [[i + j async for i in asynciter([1, 2])] for j in [10, 20]]
self.assertEqual(
run_async(run_list_inside_list()),
([], [[11, 12], [21, 22]]))
async def run_set_inside_list():
return [{i + j async for i in asynciter([1, 2])} for j in [10, 20]]
self.assertEqual(
run_async(run_set_inside_list()),
([], [{11, 12}, {21, 22}]))
async def run_list_inside_set():
return {sum([i async for i in asynciter(range(j))]) for j in [3, 5]}
self.assertEqual(
run_async(run_list_inside_set()),
([], {3, 10}))
async def run_dict_inside_dict():
return {j: {i: i + j async for i in asynciter([1, 2])} for j in [10, 20]}
self.assertEqual(
run_async(run_dict_inside_dict()),
([], {10: {1: 11, 2: 12}, 20: {1: 21, 2: 22}}))
async def run_list_inside_gen():
gen = ([i + j async for i in asynciter([1, 2])] for j in [10, 20])
return [x async for x in gen]
self.assertEqual(
run_async(run_list_inside_gen()),
([], [[11, 12], [21, 22]]))
async def run_gen_inside_list():
gens = [(i async for i in asynciter(range(j))) for j in [3, 5]]
return [x for g in gens async for x in g]
self.assertEqual(
run_async(run_gen_inside_list()),
([], [0, 1, 2, 0, 1, 2, 3, 4]))
async def run_gen_inside_gen():
gens = ((i async for i in asynciter(range(j))) for j in [3, 5])
return [x for g in gens async for x in g]
self.assertEqual(
run_async(run_gen_inside_gen()),
([], [0, 1, 2, 0, 1, 2, 3, 4]))
async def run_list_inside_list_inside_list():
return [[[i + j + k async for i in asynciter([1, 2])]
for j in [10, 20]]
for k in [100, 200]]
self.assertEqual(
run_async(run_list_inside_list_inside_list()),
([], [[[111, 112], [121, 122]], [[211, 212], [221, 222]]]))
def test_copy(self):
async def func(): pass
coro = func()

3
Misc/NEWS.d/next/Core and Builtins/2018-05-11-12-44-03.bpo-33346.ZgBkvB.rst Normal file
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@ -0,0 +1,3 @@
Asynchronous comprehensions are now allowed inside comprehensions in
asynchronous functions. Outer comprehensions implicitly become
asynchronous.

14
Python/compile.c
View File

@ -4947,11 +4947,9 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
PyCodeObject *co = NULL;
comprehension_ty outermost;
PyObject *qualname = NULL;
int scope_type = c->u->u_scope_type;
int is_async_generator = 0;
int top_level_await = IS_TOP_LEVEL_AWAIT(c);
int is_async_function = c->u->u_ste->ste_coroutine;
int is_top_level_await = IS_TOP_LEVEL_AWAIT(c);
outermost = (comprehension_ty) asdl_seq_GET(generators, 0);
if (!compiler_enter_scope(c, name, COMPILER_SCOPE_COMPREHENSION,
@ -4963,7 +4961,11 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
is_async_generator = c->u->u_ste->ste_coroutine;
if (is_async_generator && !is_async_function && type != COMP_GENEXP && !top_level_await) {
if (is_async_generator && type != COMP_GENEXP &&
scope_type != COMPILER_SCOPE_ASYNC_FUNCTION &&
scope_type != COMPILER_SCOPE_COMPREHENSION &&
!is_top_level_await)
{
compiler_error(c, "asynchronous comprehension outside of "
"an asynchronous function");
goto error_in_scope;
@ -5002,7 +5004,7 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
qualname = c->u->u_qualname;
Py_INCREF(qualname);
compiler_exit_scope(c);
if (top_level_await && is_async_generator){
if (is_top_level_await && is_async_generator){
c->u->u_ste->ste_coroutine = 1;
}
if (co == NULL)

9
Python/symtable.c
View File

@ -2056,7 +2056,14 @@ symtable_handle_comprehension(struct symtable *st, expr_ty e,
return 0;
}
st->st_cur->ste_generator = is_generator;
return symtable_exit_block(st);
int is_async = st->st_cur->ste_coroutine && !is_generator;
if (!symtable_exit_block(st)) {
return 0;
}
if (is_async) {
st->st_cur->ste_coroutine = 1;
}
return 1;
}
static int