can't structure dataclass with PEP563 postponed annotations or forward references #195
Description
- cattrs version: 1.8.0
- Python version: 3.10.0
- Operating System: macOS 12.0.1
Description
I would like to use cattrs with dataclasses (for this project I can't use attrs classes). I get the following errors when I try to structure a dataclass with circular, nested definitions that contain string literals to be post-evaluated (e.g. via typing.get_type_hints).
It seems that this currently only works with attrs classes, but not dataclasses.
What I Did
from __future__ import annotations
from typing import List
from dataclasses import dataclass, field
from cattr import Converter, GenConverter
@dataclass
class Node:
children: List[Node] = field(default_factory=list)
tree = Node([Node([Node(), Node()]), Node()])
c = GenConverter()
data = c.unstructure(tree)
# Raises: NotAnAttrsClassError: <class '__main__.Node'> is not an attrs-decorated class.
c.structure(data, Node)
c = Converter()
data = c.unstructure(tree)
# Raises: StructureHandlerNotFoundError: Unsupported type: List[Node]. Register a structure hook for it.
c.structure(data, Node)If I remove from __future__ import annotations and type the nested children: List["Node"] I get this other error:
StructureHandlerNotFoundError: Unsupported type: ForwardRef('Node'). Register a structure hook for it.