gh-111353: GenericAlias support and TypeVarLike resolution for typing.get_type_hints
#111515
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NCPlayz
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gvanrossum,
Fidget-Spinner,
JelleZijlstra and
AlexWaygood
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Wow thank you for this large improvement! I'm sorry I'm not able to review this as it's been some time since I touched that specific code (I wrote some of it but I no longer remember its intricacies). I'll defer to the rest. Thanks again. Your efforts are much appreciated! |
…ld ever hit that codepath
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I think there is a lack of tests and implementation for handling |
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Thanks @zhPavel! I've implemented some preliminary support for TypeVarTuple, which seemed to work with the test cases I added. Though, I haven't really used TypeVarTuple too much so there may be some bits that are buggy, please let me know if you find anything! |
NCPlayz
changed the title
typing.get_type_hintstyping.get_type_hints
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Thank you so much for your work on this. It's truly an essential addition that's been missing from the standard library. While testing this PR, I stumbled upon a scenario where get_type_hints throws an error when used with def test_get_type_hints_annotated_generic_typeddict(self):
class Foo(TypedDict, Generic[T]):
a: T
b: Annotated[str, 'annotation']
self.assertEqual(get_type_hints(Foo[bool]), {'a': bool, 'b': str})The error I encountered is as follows: Traceback (most recent call last):
File "/Users/.../cpython/Lib/test/test_typing.py", line 6482, in test_get_type_hints_annotated_generic_typeddict
self.assertEqual(get_type_hints(Foo[bool]), {'a': bool, 'b': str})
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/.../cpython/Lib/typing.py", line 2220, in get_type_hints
to_sub = _substitute_type_hints(param_tracking[obj], hints)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/.../cpython/Lib/typing.py", line 2414, in _substitute_type_hints
sub = _copy_with(value, new_args)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/.../cpython/Lib/typing.py", line 387, in _copy_with
return t.copy_with(new_args)
^^^^^^^^^^^^^^^^^^^^^
File "/Users/.../cpython/Lib/typing.py", line 1969, in copy_with
assert len(params) == 1
^^^^^^^^^^^^^^^^
AssertionError |
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And one more example with an error: def test_get_type_hints_unbound_typevar(self):
class Foo(Generic[T]):
x: list[T]
y: KT
self.assertEqual(gth(Foo), {'x': list[T], 'y': KT}) # ok
self.assertEqual(gth(Foo[int]), {'x': list[int], 'y': KT}) # errorError: Traceback (most recent call last):
File "/Users/.../cpython/Lib/test/test_typing.py", line 6571, in test_get_type_hints_extended_generic_rules_subclassing_with_generic
self.assertEqual(gth(Foo[int]), {'x': list[int], 'y': KT}) # error
^^^^^^^^^^^^^
File "/Users/.../cpython/Lib/typing.py", line 2220, in get_type_hints
to_sub = _substitute_type_hints(param_tracking[obj], hints)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/.../cpython/Lib/typing.py", line 2416, in _substitute_type_hints
sub = mapping[value]
~~~~~~~^^^^^^^
KeyError: ~KT |
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Thanks, but I think this doesn't need to go into CPython.
I'd prefer to limit CPython's introspection support to the minimum required for third-party packages to access typing metadata in a safe, portable way. This limits the surface area we have to maintain and enables third-party tools to provide support across many Python versions.
get_type_hintscan now resolve TypeVarLikes correctly for all generic classes, including TypedDicts.There were a lot of edge cases that I tested and subsequently wrote unit tests for.
I've also split some pre-existing code in the typing library into their own utility functions (
_copy_withto work for copying any generic type with new params and_make_substitutionfrom_GenericAlias._make_substitution).I've tried my hardest to document each step but please let me know if there are any steps that don't make sense or could be written another way.
typing.get_type_hintsdoesn't support GenericAliases #111353