resolve_types doesn't resolve types in our methods

[hynek]

While working on #716 I noticed an inconsistency: the type annotations of our methods (notably __attrs__) aren't resolved. It's especially jarring, if a type was passed via the type= parameter because then some are resolved and some aren't.

I think we should fix this, what do y'all (especially @ambv & @euresti) think?

[euresti]

I guess you're suggesting adding to attr.resolve_types? That should be possible.

[hynek]

Yes, and (mainly) asking if it makes sense or whether I'm missing something.

[euresti]

Actually now that I think about it more. I don't think we need to do this. This is what type.get_type_hints is for. And it's what PEP 563 says to use.

Oh. Now I see you mention __attrs__ specifically. Though I can't seem to find this method in the codebase. What did you mean?

[hynek]

Eh I meant __init__ – sorry!

[euresti]

Does typing.get_type_hints(A.__init__) work for this purpose?

[hynek]

I think it should, but looks like we're breaking something. :( This is from my attempt to fix test_annotations for Python 3.10:

__________________________________________________________ TestAnnotations.test_typing_annotations ___________________________________________________________

self = <tests.test_annotations.TestAnnotations object at 0x10d52f520>

    def test_typing_annotations(self):
        """
        Sets the `Attribute.type` attr from typing annotations.
        """

        @attr.s
        class C:
            x: typing.List[int] = attr.ib()
            y = attr.ib(type=typing.Optional[str])

        attr.resolve_types(C)

        assert typing.List[int] is attr.fields(C).x.type
        assert typing.Optional[str] is attr.fields(C).y.type
>       assert typing.get_type_hints(C.__init__) == {
            "x": typing.List[int],
            "y": typing.Optional[str],
            "return": type(None),
        }

tests/test_annotations.py:74:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../../.asdf/installs/python/3.10-dev/Python.framework/Versions/3.10/lib/python3.10/typing.py:1491: in get_type_hints
    value = _eval_type(value, globalns, localns)
../../.asdf/installs/python/3.10-dev/Python.framework/Versions/3.10/lib/python3.10/typing.py:279: in _eval_type
    return t._evaluate(globalns, localns, recursive_guard)
../../.asdf/installs/python/3.10-dev/Python.framework/Versions/3.10/lib/python3.10/typing.py:557: in _evaluate
    eval(self.__forward_code__, globalns, localns),
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

>   ???
E   NameError: name 'typing' is not defined

<string>:1: NameError
================================================================== short test summary info ===================================================================
FAILED tests/test_annotations.py::TestAnnotations::test_typing_annotations - NameError: name 'typing' is not defined

How bad did I screw up? 😬

[euresti]

Oh right. I remember seeing this problem before.
When you do typing.get_type_hints(C) get_type_hints will look in the entire module automatically.
https://github.com/python/cpython/blob/master/Lib/typing.py#L1454

But when you pass in a method it doesn't do that. So you have to specify the globalns yourself.

        assert typing.get_type_hints(C.__init__, globalns=sys.modules[C.__module__].__dict__) == {
            "x": typing.List[int],
            "y": typing.Optional[str],
            "return": type(None),
        }

or more succintly:

        assert typing.get_type_hints(C.__init__, globalns=globals()) == {
            "x": typing.List[int],
            "y": typing.Optional[str],
            "return": type(None),
        }

[euresti]

Ah ha!. This is #593

[hynek]

That was my big fear. 😭

[hynek]

Closing now, guess we'll have to tackle #593. 😬