8000 gh-118168: Fix Unpack interaction with builtin aliases by JelleZijlstra · Pull Request #118169 · python/cpython · GitHub
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gh-118168: Fix Unpack interaction with builtin aliases #118169

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Merged
merged 2 commits into from
Apr 23, 2024
Merged

gh-118168: Fix Unpack interaction with builtin aliases #118169

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gh-118168: Fix Unpack interaction with builtin aliases
JelleZijlstra Apr 23, 2024
5e82806
Update Lib/test/test_typing.py
JelleZijlstra Apr 23, 2024
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32 changes: 32 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -978,6 +978,38 @@ def foo(**kwargs: Unpack[Movie]): ...
self.assertEqual(repr(foo.__annotations__['kwargs']),
f"typing.Unpack[{__name__}.Movie]")

def test_builtin_tuple(self):
Ts = TypeVarTuple("Ts")

class Old(Generic[*Ts]): ...
class New[*Ts]: ...

PartOld = Old[int, *Ts]
self.assertEqual(PartOld[str].__args__, (int, str))
self.assertEqual(PartOld[*tuple[str]].__args__, (int, str))
self.assertEqual(PartOld[*Tuple[str]].__args__, (int, str))
self.assertEqual(PartOld[Unpack[tuple[str]]].__args__, (int, str))
self.assertEqual(PartOld[Unpack[Tuple[str]]].__args__, (int, str))

PartNew = New[int, *Ts]
self.assertEqual(PartNew[str].__args__, (int, str))
self.assertEqual(PartNew[*tuple[str]].__args__, (int, str))
self.assertEqual(PartNew[*Tuple[str]].__args__, (int, str))
self.assertEqual(PartNew[Unpack[tuple[str]]].__args__, (int, str))
self.assertEqual(PartNew[Unpack[Tuple[str]]].__args__, (int, str))

def test_unpack_wrong_type(self):
Ts = TypeVarTuple("Ts")
class Gen[*Ts]: ...
PartGen = Gen[int, *Ts]

bad_unpack_param = re.escape("Unpack[...] must be used with a tuple type")
with self.assertRaisesRegex(TypeError, bad_unpack_param):
PartGen[Unpack[list[int]]]
with self.assertRaisesRegex(TypeError, bad_unpack_param):
PartGen[Unpack[List[int]]]


class TypeVarTupleTests(BaseTestCase):

def assertEndsWith(self, string, tail):
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5 changes: 3 additions & 2 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1786,8 +1786,9 @@ def __typing_unpacked_tuple_args__(self):
assert self.__origin__ is Unpack
assert len(self.__args__) == 1
arg, = self.__args__
if isinstance(arg, _GenericAlias):
assert arg.__origin__ is tuple
if isinstance(arg, (_GenericAlias, types.GenericAlias)):
if arg.__origin__ is not tuple:
raise TypeError("Unpack[...] must be used with a tuple type")
Comment on lines +1789 to +1791
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@AlexWaygood AlexWaygood Apr 23, 2024 •
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It feels weirdly inconsistent that we allow nonsensical things with the new syntax, but not with the "backwards-compatible syntax":

>>> from typing import TypeVarTuple, Unpack
>>> class Foo[*Ts]: ...
...
>>> Ts = TypeVarTuple("Ts")
>>> Bar = Foo[int, *Ts]
>>> Bar[*list[str]]
__main__.Foo[int, *list[str]]
>>> Bar[Unpack[list[str]]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    Bar[Unpack[list[str]]]
    ~~~^^^^^^^^^^^^^^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 394, in inner
    return func(*args, **kwds)
           ~~~~^^^^^^^^^^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 1394, in __getitem__
    args = _unpack_args(args)
           ~~~~~~~~~~~~^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 306, in _unpack_args
    subargs = getattr(arg, '__typing_unpacked_tuple_args__', None)
              ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 1791, in __typing_unpacked_tuple_args__
    raise TypeError("Unpack[...] must be used with a tuple type")
TypeError: Unpack[...] must be used with a tuple type

But I guess that's a preexisting problem, not new to this PR. We previously discussed the issue of "all generic aliases being unpackable" in #103450.

return arg.__args__
return None

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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2024-04-22-20-42-29.gh-issue-118168.Igni7h.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix incorrect argument substitution when :data:`typing.Unpack` is used with
the builtin :class:`tuple`. :data:`!typing.Unpack` now raises
:exc:`TypeError` when used with certain invalid types. Patch by Jelle
Zijlstra.
0