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faph opened this issue Nov 20, 2023 · 2 comments
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Unioned types should be hashable: not documented? #112281

faph opened this issue Nov 20, 2023 · 2 comments
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topic-typing type-bug An unexpected behavior, bug, or error

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@faph
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faph commented Nov 20, 2023 •
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Documentation

It seems that typing.Union[X, Y] as well as X | Y type hints require X and Y to be hashable.

This is not documented as far as I can see.

Considering this example:

@dataclass
class ValueRange:
    lo: int
    hi: int

T1 = Annotated[int, ValueRange(-10, 5)]

This fails when unioned:

>>> Annotated[int, ValueRange(-10, 5)] | None
(...)
  File "/usr/lib64/python3.11/typing.py", line 1375, in __or__
    return Union[self, right]
           ~~~~~^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/typing.py", line 358, in inner
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/typing.py", line 481, in __getitem__
    return self._getitem(self, parameters)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/typing.py", line 695, in Union
    parameters = _remove_dups_flatten(parameters)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/typing.py", line 326, in _remove_dups_flatten
    return tuple(_deduplicate(params))
                 ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/typing.py", line 301, in _deduplicate
    all_params = set(params)
                 ^^^^^^^^^^^
  File "/usr/lib64/python3.11/typing.py", line 2151, in __hash__
    return hash((self.__origin__, self.__metadata__))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: unhashable type: 'ValueRange'

Should this be documented say here: https://docs.python.org/3/library/typing.html?highlight=typing#typing.Annotated ?

And examples here should use frozen dataclasses: https://docs.python.org/3/library/typing.html?highlight=typing#typing.Annotated ?

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@faph faph added the docs Documentation in the Doc dir label Nov 20, 2023
@faph faph mentioned this issue Nov 20, 2023
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sobolevn commented Nov 20, 2023 •
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PEPs https://peps.python.org/pep-0593/#specification and https://peps.python.org/pep-0604/ do not say anything about requirement of items to be hashable. I think that this is a bug: unhashable items must be allowed.

I think that we need to rework our _deduplicate function. I have an idea on how to do it :)

Thanks for the report! 👍

@sobolevn sobolevn added type-bug An unexpected behavior, bug, or error and removed docs Documentation in the Doc dir labels Nov 20, 2023
@sobolevn sobolevn self-assigned this Nov 20, 2023
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This is more complex than I initially thought, because _UnionGenericAlias also uses set to compare results. So, we need a slow way of doing it as well. See

cpython/Lib/typing.py

Line 1536 in ce1096f

return set(self.__args__) == set(other.__args__)

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pythongh-112281: Allow Union with unhashable Annotated metadata
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gh-112281: Allow Union with unhashable Annotated metadata (#112283)
a7549b0 
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Mar 1, 2024
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pythongh-112281: Allow Union with unhashable Annotated metadata (p…
21cad08 
…ythonGH-112283)

(cherry picked from commit a7549b0)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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[3.12] gh-112281: Allow Union with unhashable Annotated metadata (G…
90f75e1 
…H-112283) (#116213)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
sobolevn added a commit to sobolevn/cpython that referenced this issue Mar 3, 2024
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[3.11] pythongh-112281: Allow Union with unhashable Annotated met…
5612315 
…adata (pythonGH-112283)

(cherry picked from commit a7549b0)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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[3.11] gh-112281: Allow Union with unhashable Annotated metadata (G…
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…H-112283) (#116288)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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pythongh-112281: Allow Union with unhashable Annotated metadata (p…
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…ython#112283)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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pythongh-112281: Allow Union with unhashable Annotated metadata (p…
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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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pythongh-112281: Allow Union with unhashable Annotated metadata (p…
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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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