X | Y union syntax breaks GenericModel #4146
Comments
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Same thing with subscriptable types, with somehow simpler example: # 1.py
from __future__ import annotations
from pydantic import BaseModel
class Model(BaseModel):
foo: list[str]Obviously, python3.8 cannot evaluate |
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While i believe #4146 (comment) is answered in #2314 (comment), I'd love to bump the original issue with a slightly reduced example. Output of from typing import Generic, TypeVar
import pydantic
from pydantic import generics
DataT = TypeVar("DataT")
class MyGenericModel(generics.GenericModel, Generic[DataT]):
generic: list[DataT] | None
class A(pydantic.BaseModel):
wrapper: MyGenericModel[int]results in The same with Union from typing import Generic, TypeVar, Union
import pydantic
from pydantic import generics
DataT = TypeVar("DataT")
class MyGenericModel(generics.GenericModel, Generic[DataT]):
generic: Union[list[DataT], None]
class A(pydantic.BaseModel):
wrapper: MyGenericModel[int]seems to be working without the issue. |
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A slightly more reduced example would be: from pydantic import generics
generics.replace_types(list[str] | None, {str: int})I guess the problem is that |
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For what it's worth, on the #4970 PR, I checked that the following code runs without issue (on Python 3.11 anyway): from typing import Generic, TypeVar
import pydantic
DataT = TypeVar("DataT")
class MyGenericModel(pydantic.BaseModel, Generic[DataT]):
generic: list[DataT] | None
class A(pydantic.BaseModel):
wrapper: MyGenericModel[int]
m = MyGenericModel[int](generic=None)
print(A(wrapper=m))
# wrapper=MyGenericModel[int](generic=None) |
* Fix X | Y union syntax breaks GenericModel (#4146) * Update changes/4146-thenx.md Co-authored-by: ⬢ Samuel Colvin <s@muelcolvin.com> * Improve tests * Recreate newstyle union via typing._UnionGenericAlias * Add basic pep-604 union args order caching detection test --------- Co-authored-by: ⬢ Samuel Colvin <s@muelcolvin.com>
weird pydantic bug? issue: pydantic/pydantic#4146
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Since this is working on V2, I'll be closing this issue. 🙏 |
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I can reproduce it on Mac and windows with Python 3.9 pydantic.version.VERSION =2.2.1 from __future__ import annotations
from pydantic import BaseModel
class Model(BaseModel):
foo: list[str]
boo: int | strTypeError: unsupported operand type(s) for |: 'type' and 'type'
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PEP604-syntax requires python>=3.10 |
With Maybe catch this error and return a more meaningful message? |
Bug
Output of
python -c "import pydantic.utils; print(pydantic.utils.version_info())":Python 3.10 incorporated PEP 604, which added syntax for writing Unions as
X | Y, instead oftyping.Union[X, Y]. It seems that when this syntax is used in combination with TypeVars as part of aGenericModel, the binding of TypeVars to their types fails.Below is first a working example using
typing.Union, followed by a non-working example using|syntax, with the stack trace. The example seeks to construct aRelationshipGenericModel, and aBidirectionalMultiRelationshipmodel which contains a list of eitherRelationship[A, B]orRelationship[B, A]models:On inspection I found that at the point that the exception is thrown,
origin_typeistypes.UnionType, where it should beRelationship.Apologies if I missed an existing issue for this. I couldn't find anything in my search.
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