Root model classes are considered as an union type by mypy #11657
Description
Initial Checks
- I confirm that I'm using Pydantic V2
Description
After upgrading to pydantic 2.11.0, our mypy pre-commit check started considering root models as union type instead of just a root model instance.
After checking release notes, I think this is related to #11212, but not sure.
This only happens when using mypy with the pydantic plugin. In our mypy.ini config we have:
[mypy]
plugins = pydantic.mypy, mypy_django_plugin.main
Downgrading to pydantic 2.10.6 fixes the issue.
Example Code
class FieldName(RootModel[str]):
def __str__(self) -> str:
return self.root
def __hash__(self) -> int:
return hash(self.root)
field_name = FieldName("value")
print(field_name.root) # error: Item "str" of "FieldName | str" has no attribute "root" [union-attr]Python, Pydantic & OS Version
pydantic version: 2.10.6
pydantic-core version: 2.27.2
pydantic-core build: profile=release pgo=false
install path: /Users/antoniogamizdelgado/Library/Caches/pypoetry/virtualenvs/badger-go-p6YDoiKT-py3.12/lib/python3.12/site-packages/pydantic
python version: 3.12.4 (main, Jul 1 2024, 14:55:58) [Clang 15.0.0 (clang-1500.3.9.4)]
platform: macOS-15.3.2-arm64-arm-64bit
related packages: mypy-1.11.2 typing_extensions-4.13.0
commit: unknown
We had to downgrade to 2.10.6 to avoid the error.