get_origin difference between Python 3.6 and Python 3.7

I was hoping that using this package would make it easier to migrate between Python versions as it changes typing implementation. So I started using it with Python 3.6 but now that I tried to use working code on Python 3.6 with Python 3.7 it seems there are differences. For example, the following code:

import typing
import typing_inspect

A = typing.TypeVar('A')
B = typing.TypeVar('B')
C = typing.TypeVar('C')

class Base(typing.Generic[A, B]):
    pass

class Foo(Base[A, None]):
    pass

class Bar(Foo[A], typing.Generic[A, C]):
    pass

class Baz(Bar[float, int]):
    pass

print("Bar", typing_inspect.get_origin(Bar))
print("Baz", typing_inspect.get_origin(Baz))
print("Base", typing_inspect.get_origin(Base))
print("Base[float, int]", typing_inspect.get_origin(Base[float, int]))
print("Foo", typing_inspect.get_origin(Foo))
print("Foo[float]", typing_inspect.get_origin(Foo[float]))

In Python 3.6 outputs:

Bar __main__.Bar
Baz __main__.Baz
Base __main__.Base
Base[float, int] __main__.Base
Foo __main__.Foo
Foo[float] __main__.Foo

While in Python 3.7:

Bar None
Baz None
Base None
Base[float, int] <class '__main__.Base'>
Foo None
Foo[float] <class '__main__.Foo'>

I think ideally they should behave the same.

[jph00]

I was always think about this, but it may be a breaking change, so I’m not 100% sure.

I suspect there are a lot more people that aren’t able to use this (or need hacky workarounds) because of the inconsistency with 3.6, than there are people relying on the existing behavior (if any). So I think fixing it would be best.

Just my $0.02 😃

[ilevkivskyi]

Yea, it would be great if then get_origin from this package would work on 3.6 the same as it does on 3.7 and 3.8.

I was always think about this, but it may be a breaking change, so I’m not 100% sure.