[3.14] Address invalid inputs of TypeAliasType #477
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Also draft for others
- compatibility tests have their own test - skip tests for appropriate python versions
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I merged the upstream PR but did not backport it to 3.12 and 3.13, so this should now be ready to go. I'll push some buttons to do so and then review the code. |
src/test_typing_extensions.py
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| for case, msg in invalid_cases: | ||
| with self.subTest(type_params=case): | ||
| if TYPING_3_12_0 and sys.version_info < (3, 14): | ||
| self.skipTest("No backport for 3.12 and 3.13 requires cpython PR #124795") |
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We decided not to backport in CPython. This test should be changed so that typing_extensions does provide the backport.
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As TypeAliasType cannot be subclassed, I tried to do a minimal invasive workaround with __new__ to return the typing variant but this fails the pickling check.
Do you know a workaround or is this __new__ method not something to pursue further?
At the moment the <3.12 backport would pass the test and would work as a full backport for 3.12 & 3.13.
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I think we can just use the pre-3.12 variant on 3.12 and 3.13.
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Guess with annotationlib (likely?) comming it needs a backport anyway.
src/typing_extensions.py
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| parameters = [] | ||
| for type_param in type_params: | ||
| if not isinstance(type_param, (TypeVar, TypeVarTuple, ParamSpec)): |
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This needs to accept both the typing and typing_extensions versions of these classes, which are different on some versions. Test this.
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Yes, I saw this too, but realized that _TypeVarLikeMeta handles isinstance check. test_type_params_compatibilitytest_type_var_compatibility and the other methods test this.
…' into TypeAliasType/invalid_param_spec
Daraan
changed the title
src/test_typing_extensions.py
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| ((1,), "Expected a type param, got 1"), | ||
| ((str,), f"Expected a type param, got {str!r}"), | ||
| # Unpack backport behaves like TypeVar in some cases |
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What "some cases" exactly? Ideally this should be accepted.
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Updated the comment for more clarity. As isinstance(Unpack[Ts], TypeVar) is True in Python < 3.12 Unpack would not raise here without the additional check and would be accepted as a type parameter.
for type_param in type_params:
if (not isinstance(type_param, (TypeVar, TypeVarTuple, ParamSpec))
or _is_unpack(type_param)
):
raise TypeError(f"Expected a type param, got {type_param!r}")
I've prepared this draft which contains two changes:
typing_extensions.TypeAliasTypenot raising TypeError if a non-tuple is passed compared to thetypingvariant.backport of
gh-124787: Fix
TypeAliasTypeand incorrecttype_paramscpython#124795 for <=3.11 (needs to be accepted first)Await merge and change if necessary
Afterwards fix correct python versions. I currently assume the backport is valid in 3.14.
Should backport for 3.12-13 be made? Yes.
It should maybe noted that for 3.12.0-3.12.7 the
typing.TypeAliasTypevariant does not contain this stricter backport.I do not think that there is a necessity to do a backport for 3.12 and it will likely do more harm (I did not test it).