New submission from Mehdi2277 <[email protected]>:
This is two closely related issues with get_type_hints on an optional annotated
member. I'm testing with Annotated/get_type_hints from typing extensions on 3.8
and assuming they're backport equivalent to current behavior.
The first issue is get_type_hints has inconsistent behavior depending on
whether annotation comes from a function with a None default or an attribute
with a None default.
class Foo:
def __init__(
self,
x:
Annotated[Optional[str], "doc string"] = None,
):
...
class Foo2:
x: Annotated[Optional[str], "doc string"] = None
get_type_hints(Foo.__init__)
# {'x': typing.Union[typing_extensions.Annotated[typing.Union[str, NoneType],
'doc string'], NoneType]}
get_type_hints(Foo2)
# {'x': typing_extensions.Annotated[typing.Union[str, NoneType], 'doc string']}
Attributes with a None default are not wrapped by get_type_hints, but function
parameters. Which of the two behaviors is correct I don't know, but I'd expect
the two to be equivalent annotations.
The second issue is for function arguments with a None default the optional
wrapper happens even if the type inside annotated already has optional. Example,
from typing_extensions import Annotated, get_type_hints
class Foo:
def __init__(
self,
x:
Annotated[Optional[str], "doc string"] = None,
):
...
get_type_hints(Foo.__init__, include_extras=True)
# {'x': typing.Union[typing_extensions.Annotated[typing.Union[str, NoneType],
'doc string'], NoneType]}
For Annotated types I would expect any type rules like wrapping to apply only
to the first argument and not the entire annotation. I mainly ran into this for
a runtime type introspection library (similar in spirit to pydantic).
As a note include_extras being True or False while it changes type is an issue
in either case. With include_extras as False the Annotated goes away, but the
type still gets double wrapped as an Optional.
----------
messages: 409319
nosy: gvanrossum, kj, med2277
priority: normal
severity: normal
status: open
title: Annotated and Optional get_type_hints buggy interaction
versions: Python 3.8
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Python tracker <[email protected]>
<https://bugs.python.org/issue46195>
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