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[3.14] GH-135171: Revert async generator expressions behavior #135352

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[3.14] GH-135171: Revert async generator expressions behavior #135352

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d04629b
[3.14] GH-135171: Revert async generator expressions behavior
efimov-mikhail Jun 10, 2025
53bd362
[3.14] GH-135171: Bug fix, test improved
efimov-mikhail Jun 10, 2025
75e6184
[3.14] GH-135171: Bug fix 2, all related changes in codegen.c are rev…
efimov-mikhail Jun 10, 2025
549cd11
Test for async generator is added
efimov-mikhail Jun 11, 2025
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7 changes: 7 additions & 0 deletions Lib/test/test_asyncgen.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1835,6 +1835,13 @@ async def run():
res = self.loop.run_until_complete(run())
self.assertEqual(res, [i * 2 for i in range(1, 10)])

def test_async_gen_expression_incorrect(self):
err_msg_async = "'async for' requires an object with " \
"__aiter__ method, got .*"

with self.assertRaisesRegex(TypeError, err_msg_async):
(x async for x in None)

def test_asyncgen_nonstarted_hooks_are_cancellable(self):
# See https://bugs.python.org/issue38013
messages = []
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-06-10-17-37-11.gh-issue-135171.P9UDfS.rst
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@@ -0,0 +1,2 @@
Reverts the behavior of async generator expressions when created with object
w/o __aiter__ method to the pre-3.13 behavior of raising a TypeError.
12 changes: 8 additions & 4 deletions Python/codegen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4544,9 +4544,9 @@ codegen_async_comprehension_generator(compiler *c, location loc,
else {
/* Sub-iter - calculate on the fly */
VISIT(c, expr, gen->iter);
ADDOP(c, LOC(gen->iter), GET_AITER);
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Hm, is this change necessary? I think the test passes without it.

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I think so. There was a bug in previous commit. I've reverted related logic in codegen.c.

}
}
ADDOP(c, LOC(gen->iter), GET_AITER);

USE_LABEL(c, start);
/* Runtime will push a block here, so we need to account for that */
Expand Down Expand Up @@ -4776,7 +4776,6 @@ codegen_comprehension(compiler *c, expr_ty e, int type,
location loc = LOC(e);

outermost = (comprehension_ty) asdl_seq_GET(generators, 0);
int is_sync_genexpr = type == COMP_GENEXP && !outermost->is_async;
if (is_inlined) {
VISIT(c, expr, outermost->iter);
if (push_inlined_comprehension_state(c, loc, entry, &inline_state)) {
Expand Down Expand Up @@ -4853,8 +4852,13 @@ codegen_comprehension(compiler *c, expr_ty e, int type,
Py_CLEAR(co);

VISIT(c, expr, outermost->iter);
if (is_sync_genexpr) {
ADDOP(c, loc, GET_ITER);
if (type == COMP_GENEXP) {
if (outermost->is_async) {
ADDOP(c, loc, GET_AITER);
}
else {
ADDOP(c, loc, GET_ITER);
}
}
ADDOP_I(c, loc, CALL, 0);

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