Option to error on unused arguments in config/parsing?

[dlwh]

Hi @lebrice

I'm migrating over from pyrallis.

One difference I'm noticing is that :

1. there's no convenience method for decoding a type from a "json/serialized value"
2. get_decoding_fn returns a Callable[[C], C] which isn't really right (i imagine it should be Callable[[some serialized type union], C])
3. the dataclass decoding function that exists does not error out if there are unused entries in the dict.

Is there any way to support (3)? (1) and (2) are minor and I'm happy to send a PR

[dlwh]

That is, I'd expect this test to pass, or have an option to pass:

def test_unused_args_errors():
    @dataclasses.dataclass
    class Person:
        name: str
        age: int

    with pytest.raises(ValueError):
        get_decoding_fn(Person)({"name": "bob", "age": 10, "id": 42})  # type: ignore

[dlwh]

oh i see, you have to use from_dict(Person, {"name": "bob", "age": 10, "id": 42}, drop_extra_fields=False)