Allow structuring union types of primitives that don't need any conversion #278
Description
- cattrs version: current master
- Python version: 3.10
- Operating System: Linux
- Let me know when you get annoyed by my issues ;)
Description
cattrs supports passing through primitives as well as the type Literal["foo", "bar"]
I have three examples of types that cattrs currently does not support:
Union[int, typing.Literal["foo"]]Union[Literal["a", "b"], Literal["c", "d"]]T2 = NewType("T2", str)thenLiteral["train", "test"] | T2)
I think cattrs should pass through all forms of combinations of primitives, literals, and primitive newtypes.
Here's an implementation that works for me:
def is_primitive_or_primitive_union(t: Any) -> bool:
"""returns true if given type is something that doesn't need ser/deser"""
if t in (str, bytes, int, float, bool):
return True
origin = typing.get_origin(t)
if origin is typing.Literal:
return True
if (basetype := cattrs._compat.get_newtype_base(t)) is not None:
return is_primitive_or_primitive_union(basetype)
if origin in (types.UnionType, typing.Union):
return all(is_primitive_or_primitive_union(ty) for ty in typing.get_args(t))
[...]
_converter.register_structure_hook_func(
is_primitive_or_primitive_union, lambda v, ty: v
)
if __name__ == "__main__":
T2 = NewType("T2", str)
print(is_primitive_or_primitive_union(Union[int, typing.Literal["silu"]]))
print(is_primitive_or_primitive_union(Union[Literal["a", "b"], Literal["c", "d"]]))
print(is_primitive_or_primitive_union(Literal["train", "val", "test"] | T2))