Need to call `attrs.resolve_types` before using `structure_attrs_fromdict`

[danarmak]

With PEP 563 enabled, the attrs field types are string values even if the original type annotation was not a string:

from __future__ import annotations
import attrs, cattrs

@attrs.define
class Foo:
    name: str

assert attrs.fields(Foo).name.type == 'str' # rather than the type str

Calling converter.structure would work, but converter.structure_attrs_fromdict fails:

assert converter.structure_attrs_fromdict({ "name": "foo" }, Foo) == Foo('foo')

Traceback (most recent call last):
  File "/home/danarmak/sb/aoa/agentune-analyze/agentune/playground.py", line 17, in <module>
    assert converter.structure_attrs_fromdict({ "name": "foo" }, Foo) == Foo('foo')
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/danarmak/.cache/pypoetry/virtualenvs/agentune-analyze-y3VXCvbo-py3.12/lib/python3.12/site-packages/cattrs/converters.py", line 779, in structure_attrs_fromdict
    conv_obj[getattr(a, "alias", a.name)] = self._structure_attribute(a, val)
                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/danarmak/.cache/pypoetry/virtualenvs/agentune-analyze-y3VXCvbo-py3.12/lib/python3.12/site-packages/cattrs/converters.py", line 760, in _structure_attribute
    return self._structure_func.dispatch(type_)(value, type_)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/danarmak/.cache/pypoetry/virtualenvs/agentune-analyze-y3VXCvbo-py3.12/lib/python3.12/site-packages/cattrs/dispatch.py", line 134, in dispatch_without_caching
    return res if res is not None else self._fallback_factory(typ)
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/danarmak/.cache/pypoetry/virtualenvs/agentune-analyze-y3VXCvbo-py3.12/lib/python3.12/site-packages/cattrs/converters.py", line 1064, in <lambda>
    structure_fallback_factory: HookFactory[StructureHook] = lambda t: raise_error(
                                                                       ^^^^^^^^^^^^
  File "/home/danarmak/.cache/pypoetry/virtualenvs/agentune-analyze-y3VXCvbo-py3.12/lib/python3.12/site-packages/cattrs/fns.py", line 22, in raise_error
    raise StructureHandlerNotFoundError(msg, type_=cl)
cattrs.errors.StructureHandlerNotFoundError: Unsupported type: 'str'. Register a structure hook for it.

Context: I'm using structure_attrs_fromdict from a custom hook factory which manipulates the dict before passing it to the builtin logic. I can't call structure because that recurses into my hook, and I can't precache the default converter hooks because I don't know all the concrete types I will need to handle ahead of time.

I'm not sure how this can be improved in cattrs, other than calling resolve_types in structure_attrs_fromdict as well as the other places that call it, which may have downsides I'm not aware of.

[danarmak]

Addendum: I'm not sure in which situations it's best to call structure_attrs_fromdict vs gen_structure_attrs_fromdict (and cache the latter).

In my case, gen_structure_attrs_fromdict fails because the class is generic; the generic type param doesn't affect any attrs fields, only some method signatures. (I'm passing the result of typing.get_origin.) This is a weird edge case where it's reasonable for cattrs to fail, so ignoring that for the moment, should I be using gen_structure_attrs_fromdict?

[Tinche]

structure_attrs_fromdict is very legacy, so I didn't update it to resolve the types. I almost always recommend using the cattrs.gen.make_dict_structure_fn hook factory instead.

If you need assistance with it I'm happy to help debug a minimal reproducible example.