[Bug] from __future__ import annotations

[jmolinski]

Hello!

from __future__ import annotations literally destroys the library.

Quick example:

foo.py

from __future__ import annotations

from dataclasses import dataclass


@dataclass
class Spam:
    eggs: int


@dataclass
class Baz:
    qux: int
    spam: Spam

bar.py

from typing import List

import jsons

from foo import Baz

data = [{"qux": 0, "spam": {"eggs": 1}}]

x = jsons.load(data, List[Baz])

Expected result: [Baz(qux=0, spam=Spam(eggs=1))]
Result:

>>> import bar
Traceback (most recent call last):
  File "/home/glen/traktpy/venv/lib/python3.7/site-packages/jsons/_main_impl.py", line 146, in load
    return deserializer(json_obj, cls, **kwargs_)
TypeError: 'NoneType' object is not callable

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

...

  File "/home/glen/traktpy/venv/lib/python3.7/site-packages/jsons/_main_impl.py", line 150, in load
    raise DeserializationError(str(err), json_obj, cls)
jsons.exceptions.DeserializationError: 'NoneType' object is not callable
>>> 

If you remove from __future__ import annotations from foo.py everything works as expected.

https://www.python.org/dev/peps/pep-0563/
from __future__ import annotations stops the interpreter from executing type annotations, they are stored as str instead. Types may be revealed during runtime using typing.get_type_hints(). This is going to be the default behavior in python4.

[ramonhagenaars]

Hello jmolinsky. This looks serious, thank you for reporting it.

[ramonhagenaars]

This has been solved in 0.8.4.