Skip to content

configure_tagged_union fails on recursive structures #678

@adament

Description

@adament
from __future__ import annotations

from attrs import define
from cattrs import Converter
from cattrs.strategies import configure_tagged_union

@define
class Add:
    left: Expr
    right: Expr

type Expr = Add | float

conv = Converter()
configure_tagged_union(Expr, conv)
conv.unstructure(Add(2.0, Add(3.0, Add(4.0, 1.0))), Expr)

fails with

Traceback (most recent call last):
  File "C:\Code\repos\arp_strategies\risk_target\cattrs_exp.py", line 15, in <module>
    configure_tagged_union(Expr, conv)
    ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\strategies\_unions.py", line 59, in configure_tagged_union
    struct_handler = converter.get_structure_hook(cl)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\converters.py", line 592, in get_structure_hook
    self._structure_func.dispatch(type)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\dispatch.py", line 133, in dispatch_without_caching
    res = self._function_dispatch.dispatch(typ)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\dispatch.py", line 76, in dispatch
    return handler(typ)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\converters.py", line 1296, in gen_structure_attrs_fromdict
    return make_dict_structure_fn(
        cl,
    ...<4 lines>...
        **attrib_overrides,
    )
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\gen\__init__.py", line 747, in make_dict_structure_fn
    return make_dict_structure_fn_from_attrs(
        attrs,
    ...<9 lines>...
        **kwargs,
    )
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\gen\__init__.py", line 388, in make_dict_structure_fn_from_attrs
    handler = find_structure_handler(
        a, t, converter, _cattrs_prefer_attrib_converters
    )
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\gen\_shared.py", line 58, in find_structure_handler
    handler = c.get_structure_hook(type, cache_result=False)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\converters.py", line 594, in get_structure_hook
    else self._structure_func.dispatch_without_caching(type)
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\dispatch.py", line 133, in dispatch_without_caching
    res = self._function_dispatch.dispatch(typ)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\dispatch.py", line 75, in dispatch
    return handler(typ, self._converter)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\typealiases.py", line 53, in type_alias_structure_factory
    res = converter.get_structure_hook(base)
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\converters.py", line 592, in get_structure_hook
    self._structure_func.dispatch(type)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\dispatch.py", line 134, in dispatch_without_caching
    return res if res is not None else self._fallback_factory(typ)
                                       ~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\converters.py", line 1050, in <lambda>
    structure_fallback_factory: HookFactory[StructureHook] = lambda t: raise_error(
                                                                       ~~~~~~~~~~~^
        None, t
        ^^^^^^^
    ),
    ^
  File "C:\Code\cache\rattler\cached-envs-v0\python-c8bda09852e34bf9\Lib\site-packages\cattrs\fns.py", line 22, in raise_error
    raise StructureHandlerNotFoundError(msg, type_=cl)
cattrs.errors.StructureHandlerNotFoundError: Unsupported type: __main__.Add | float. Register a structure hook for it.

Metadata

Metadata

Assignees

No one assigned

    Labels

    No labels
    No labels

    Type

    No type

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions