RootModel with Generics with self-referencing fails to compile #11748
Description
Initial Checks
- I confirm that I'm using Pydantic V2
Description
Hi Pydantic team, absolutely love your work!
Hopefully this isn't too gnarly of an issue to debug 😅
When I run the code below it works for pydantic v2.10.6 but with v2.11.3 it results in this error
AttributeError: __pydantic_fields__. Did you mean: '__pydantic_fields_set__'?
Full stack trace:
Traceback (most recent call last):
File "/Users/first.last/Downloads/tmp/./tmp.py", line 16, in <module>
class Branch(BaseModel):
...<2 lines>...
children: "PydList[Leaf|Branch]"
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_model_construction.py", line 221, in __new__
set_model_fields(cls, config_wrapper=config_wrapper, ns_resolver=ns_resolver)
~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_model_construction.py", line 544, in set_model_fields
fields, class_vars = collect_model_fields(cls, config_wrapper, ns_resolver, typevars_map=typevars_map)
~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_fields.py", line 118, in collect_model_fields
type_hints = _typing_extra.get_model_type_hints(cls, ns_resolver=ns_resolver)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_typing_extra.py", line 329, in get_model_type_hints
hints[name] = try_eval_type(value, globalns, localns)
~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_typing_extra.py", line 378, in try_eval_type
return eval_type_backport(value, globalns, localns), True
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_typing_extra.py", line 429, in eval_type_backport
return _eval_type_backport(value, globalns, localns, type_params)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_typing_extra.py", line 466, in _eval_type_backport
return _eval_type(value, globalns, localns, type_params)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_typing_extra.py", line 496, in _eval_type
return typing._eval_type( # type: ignore
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
value, globalns, localns, type_params=type_params
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/Users/first.last/.pyenv/versions/3.13.1/lib/python3.13/typing.py", line 474, in _eval_type
return t._evaluate(globalns, localns, type_params, recursive_guard=recursive_guard)
~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/.pyenv/versions/3.13.1/lib/python3.13/typing.py", line 1081, in _evaluate
eval(self.__forward_code__, globalns, localns),
~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "<string>", line 1, in <module>
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/main.py", line 909, in __class_getitem__
submodel = _generics.create_generic_submodel(model_name, origin, args, params)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generics.py", line 128, in create_generic_submodel
created_model = meta(
model_name,
...<8 lines>...
**kwds,
)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_model_construction.py", line 237, in __new__
complete_model_class(
~~~~~~~~~~~~~~~~~~~~^
cls,
^^^^
...<3 lines>...
create_model_module=_create_model_module,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_model_construction.py", line 597, in complete_model_class
schema = gen_schema.generate_schema(cls)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 706, in generate_schema
schema = self._generate_schema_inner(obj)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 984, in _generate_schema_inner
return self._model_schema(obj)
~~~~~~~~~~~~~~~~~~^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 802, in _model_schema
root_field = self._common_field_schema('root', fields['root'], decorators)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 1352, in _common_field_schema
schema = self._apply_annotations(
source_type,
annotations + validators_from_decorators,
)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 2264, in _apply_annotations
schema = get_inner_schema(source_type)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_schema_generation_shared.py", line 83, in __call__
schema = self._handler(source_type)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 2246, in inner_handler
schema = self._generate_schema_inner(obj)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 989, in _generate_schema_inner
return self.match_type(obj)
~~~~~~~~~~~~~~~^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 1103, in match_type
return self._match_generic_type(obj, origin)
~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 1130, in _match_generic_type
return self._list_schema(self._get_first_arg_or_any(obj))
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 367, in _list_schema
return core_schema.list_schema(self.generate_schema(items_type))
~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 706, in generate_schema
schema = self._generate_schema_inner(obj)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 989, in _generate_schema_inner
return self.match_type(obj)
~~~~~~~~~~~~~~~^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 1103, in match_type
return self._match_generic_type(obj, origin)
~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 1126, in _match_generic_type
return self._union_schema(obj)
~~~~~~~~~~~~~~~~~~^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 1414, in _union_schema
choices.append(self.generate_schema(arg))
~~~~~~~~~~~~~~~~~~~~^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 706, in generate_schema
schema = self._generate_schema_inner(obj)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 984, in _generate_schema_inner
return self._model_schema(obj)
~~~~~~~~~~~~~~~~~~^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_generate_schema.py", line 745, in _model_schema
fields = rebuild_model_fields(
cls,
ns_resolver=self._ns_resolver,
typevars_map=self._typevars_map or {},
)
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_fields.py", line 318, in rebuild_model_fields
for f_name, field_info in cls.__pydantic_fields__.items():
^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic/_internal/_model_construction.py", line 271, in __getattr__
raise AttributeError(item)
AttributeError: __pydantic_fields__. Did you mean: '__pydantic_fields_set__'?
Example Code
"""Works for pydantic 2.10.6 but not for 2.11.3"""
from typing import TypeVar
from pydantic import BaseModel, RootModel
T = TypeVar('T')
class PydList(RootModel[list[T]]):
"""Pydantic List Model that supports .model_dump()"""
class Leaf(BaseModel):
"""Leaf Model"""
text: str
class Branch(BaseModel):
"""Branch Model"""
val: str # using `val` instead of `text` like `Leaf` model to hopefully help debug / avoid red herring
children: "PydList[Leaf|Branch]" # <- self reference
a = {
"val": "asdf",
"children": [
{
"text": "asdf"
},
{
"val": "asdf",
"children": [
{
"text": "asdf"
}
]
}
]
}
b = Branch.model_validate(a)Python, Pydantic & OS Version
pydantic version: 2.11.3
pydantic-core version: 2.33.1
pydantic-core build: profile=release pgo=false
install path: /Users/first.last/Downloads/tmp/env/lib/python3.13/site-packages/pydantic
python version: 3.13.1 (main, Jan 28 2025, 14:38:43) [Clang 16.0.0 (clang-1600.0.26.6)]
platform: macOS-15.4-arm64-arm-64bit-Mach-O
related packages: typing_extensions-4.13.2
commit: unknown