dataclass decorator not working as expected

[rafi-cohen]

Hi,

I seem to be running into a couple of issues when using the decorator that was recently added in #9:

1. It does not work with optional keyword arguments:

from argparse_dataclass import dataclass

@dataclass(frozen=True)
class Opt:
    x: int = 42
    y: bool = False

Error: TypeError: cls must be a dataclass
It seems that cls here is actually real_dataclass.wrap.

2. It does not behave like a regular dataclass:

from argparse_dataclass import dataclass

@dataclass
class Opt:
    x: int = 42
    y: bool = False

opt = Opt()
print(opt.x)

Error: AttributeError: 'Inner' object has no attribute 'x'
Looks like Opt was "replaced" with Inner, which is defined in argparse_dataclass.dataclass.

[rafi-cohen]

I think 1 can be fixed by doing something similar to real_dataclass - the return value depends on whether it was called with parentheses or not.
And 2 can probably be fixed by not defining a new class, but rather modifying the class we're decorating.

I'll try it out soon.