[BUG] from_json of class with attribute of list of types which inherit basic types results in wrong result

[nirh-cye]

Description

I have a dataclass that holds an attribute of list (if names was type of name and not list of Name, issue would not reproduce) of a class that inherits the basic type: string. When creating an instance of this class, converting it into json, writing said json to a file and later reading it and re-creating the object from it, the object structure is not identical to the previous object structure. The attribute of list that contains objects which inherit the basic type creates the list objects as the basic type instead of their expected type.

Code snippet that reproduces the issue

import json

from dataclasses import dataclass
from dataclasses_json import DataClassJsonMixin

class Name(str):
    ...

@dataclass
class Person(DataClassJsonMixin):
    names: list[Name]

if __name__ == '__main__':
    johnny = Person(names=[Name('John Doe')])
    with open('storage.json', 'w') as f:
        json.dump(johnny.to_json(), f)

    ...

    with open('storage.json', 'r') as f:
        johnny_again = Person.from_json(json.load(f))

    print(isinstance(johnny_again.names[0], Name))  # prints: False

Describe the results you expected

As the original type was indeed Name (before being written into the file) I expected the object after reading the json to also be Name

Python version you are using

3.10

Environment description

Standard clean env. only used pip install dataclasses-json

[george-zubrienko]

I am not sure what is happening here:

with open('storage.json', 'w') as f:
        json.dump(johnny.to_json(), f)

johnny.to_json already returns a string. If you do f.write(johnny.to_json()), do you still have an issue?

[nirh-cye]

johnny.to_json already returns a string. If you do f.write(johnny.to_json()), do you still have an issue?

Yes, the reason I am writing to a file in this example is that Person.from_json(johnny.to_json()) would indeed work as expected, the reason being that johnny.to_json would not change the names inner elements to string, it would leave them as they are and therefore would not convert them back in the from_json function.

When this is written to a file, the text: '{"names": ["John Doe"]}' is dumped into it. when attempting to convert that into Person via the Person.from_json function, the type of the names elements will indeed be incorrect.

In short, the writing into a file is not required and the following will also reproduce this bug:

from dataclasses import dataclass
from dataclasses_json import DataClassJsonMixin

class Name(str):
    ...

@dataclass
class Person(DataClassJsonMixin):
    names: list[Name]

if __name__ == '__main__':
    js = '{"names": ["John Doe"]}'
    print(isinstance(Person.from_json(js).names[0], Name))  # prints: False

[george-zubrienko]

I'll retest this on latest commit tomorrow to see if this is some similar issue with 3.10 as with self-types