Deserialization issues with dataclasses in dictionaries

[camilanovaes]

• Dataclass Wizard version: 0.32.0
• Python version: 3.10.12
• Operating System: Ubuntu 22.04.5 LTS

Description

The code provided worked in version 0.30.1 but stopped working in versions 0.31.0 and 0.32.0. The issue happens when using a dataclass in a dictionary (i.e., dict[str, Test]).

What I Did

Code example:

from dataclasses import dataclass
from dataclass_wizard import fromdict

config = {"tests": {"test_a": {"field": "a"}, "test_b": {"field": "b"}}}

@dataclass
class Test:
    field: str
    
@dataclass
class Config:
    tests: dict[str, Test]

test_config = fromdict(Config, config)
print(test_config)

Traceback:

Traceback (most recent call last):
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/loaders.py", line 592, in fromdict
    load = CLASS_TO_LOAD_FUNC[cls]
KeyError: <class '__main__.Config'>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/camila/work/test_datawizard.py", line 18, in <module>
    test_config = fromdict(Config, config)
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/loaders.py", line 594, in fromdict
    load = load_func_for_dataclass(cls)
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/loaders.py", line 650, in load_func_for_dataclass
    field_to_parser = dataclass_field_to_load_parser(cls_loader, cls, config)
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/class_helper.py", line 131, in dataclass_field_to_load_parser
    return _setup_load_config_for_cls(cls_loader, cls, config, save)
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/class_helper.py", line 211, in _setup_load_config_for_cls
    name_to_parser[f.name] = getattr(p := cls_loader.get_parser_for_annotation(
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/loaders.py", line 416, in get_parser_for_annotation
    return MappingParser(
  File "<string>", line 5, in __init__
  File "/home/camila/.virtualenvs/gn/lib/python3.10/site-packages/dataclass_wizard/parsers.py", line 559, in __post_init__
    self.val_base_type = val_parser.base_type
AttributeError: 'function' object has no attribute 'base_type'

Expected:

Config(tests={'test_a': Test(field='a'), 'test_b': Test(field='b')})

[rnag]

Hi @camilanovaes 👋,

Thank you for opening this issue and providing a minimal example!

I’ve confirmed it’s a bug and identified the cause. While I initially thought all uses of base_type were confined to UnionParser, it seems I missed one 😅.

I’ll be working on a bugfix patch for this shortly — stay tuned!

[rnag]

I forgot to link the PR, but this is now fixed in v0.32.1, as part of #162 🙌 . Also added a test case to confirm intended functionality.

[camilanovaes]

Amazing, @rnag !
Thanks!! 😃