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Thus, get_type_hints is unable to resolve the types for annotations that are only imported in foo.py.
I ran this example using typing_extensions 3.7.4.2 (released via #709) and Python 3.7.3, but it seems like this would be an issue using the current main branches of both repositories as well.
I'm wondering what the right approach is to tackling this issue. It is of course solvable by defining Bar in foo.py instead, but it isn't ideal or intuitive to always need to inherit from a TypedDict in the same module.
I was thinking that similarly to __required_keys__ and __optional_keys__, the TypedDict could preserve its original bases in a new dunder attribute, and get_type_hints could work off of that instead of MRO when it is dealing with a TypedDict. I would be willing to contribute the PRs to implement this if the design is acceptable, but am open to other ideas as well.
The text was updated successfully, but these errors were encountered:
Hi @keithblaha, can you also file this on bugs.python.org? It is relevant for Python 3.10 which will turn on this behavior by default. (In fact it probably isn't going to be fixed anywhere except in the 3.9 and 3.10 stdlib versions of typing.py -- and maybe 3.8.)
I came across this issue while using inheritance to express required keys in a
TypedDict
, as is recommended by the docs.It's most easily explained by a minimal example I cooked up. Let's say we have a module
foo.py
:And another module
bar.py
:Note that both
foo.py
andbar.py
have adopted postponed evaluation of annotations (PEP 563) by using the__future__
import.If we execute
bar.py
, we get the error messageNameError: name 'Optional' is not defined
.This is due to the combination of:
get_type_hints
relies on the MRO to resolve types: https://github.com/python/cpython/blob/3.7/Lib/typing.py#L970TypedDict
does not preserve the original bases, soFoo
is not in the MRO forBar
:typing/typing_extensions/src_py3/typing_extensions.py
Line 1652 in d79edde
Thus,
get_type_hints
is unable to resolve the types for annotations that are only imported infoo.py
.I ran this example using typing_extensions 3.7.4.2 (released via #709) and Python 3.7.3, but it seems like this would be an issue using the current main branches of both repositories as well.
I'm wondering what the right approach is to tackling this issue. It is of course solvable by defining
Bar
infoo.py
instead, but it isn't ideal or intuitive to always need to inherit from aTypedDict
in the same module.I was thinking that similarly to
__required_keys__
and__optional_keys__
, theTypedDict
could preserve its original bases in a new dunder attribute, andget_type_hints
could work off of that instead of MRO when it is dealing with aTypedDict
. I would be willing to contribute the PRs to implement this if the design is acceptable, but am open to other ideas as well.The text was updated successfully, but these errors were encountered: