Does not work when from __future__ import annotations is in scope

[ykrasik]

Hi,

The following example will not work

from __future__ import annotations
from dataclasses import dataclass
import dataconf

@dataclass
class Test:
    my_var: str

conf = """
my_var = test
"""

print(dataconf.string(conf, Test))

Getting this error:

  File "...\.venv\Lib\site-packages\dataconf\main.py", line 108, in string
    return multi.string(s, **kwargs).on(clazz)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "...\.venv\Lib\site-packages\dataconf\main.py", line 93, in on
    return parse(conf, clazz, self.strict, **self.kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "...\.venv\Lib\site-packages\dataconf\main.py", line 26, in parse
    return utils.__parse(conf, clazz, "", strict, ignore_unexpected)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "...\.venv\Lib\site-packages\dataconf\utils.py", line 91, in __parse
    fs[f.name] = __parse(
                 ^^^^^^^^
  File "...\.venv\Lib\site-packages\dataconf\utils.py", line 269, in __parse
    subtype = value.pop("_type", default=None)
              ^^^^^^^^^
AttributeError: 'str' object has no attribute 'pop'

This line does not pass because when from __future__ import annotations, dataclass.fields returns the type as a string whose value is "str" rather then the class str. There are some more details about this here: https://stackoverflow.com/a/55938344

According to the above StackOverflow, the way to fix it is to not rely on the type from the field, but get it from typing.get_type_hints:

resolved = typing.get_type_hints(C)
f = dataclasses.fields(C)[0]
ftype = resolved[f.name]

[ykrasik]

Woops, duplicate of #43

[zifeo]

See indeed #43 (comment).