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Combining string enums with generics results in stack overflow in Pydantic 1.8 #2436

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janheindejong opened this issue Mar 1, 2021 · 2 comments · Fixed by #2438
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bug V1 Bug related to Pydantic V1.X


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janheindejong commented Mar 1, 2021


  • I added a descriptive title to this issue
  • I have searched (google, github) for similar issues and couldn't find anything
  • I have read and followed the docs and still think this is a bug


Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.7.3
            pydantic compiled: True
                 install path: C:\Soft_Dev\LIVE_tls_application\back_end\.venv\Lib\site-packages\pydantic
               python version: 3.9.1 (tags/v3.9.1:1e5d33e, Dec  7 2020, 17:08:21) [MSC v.1927 64 bit (AMD64)]
                     platform: Windows-10-10.0.18362-SP0
     optional deps. installed: ['typing-extensions']

Love Pydantic, great stuff, etc etc.

I came across a bug in the following code (which works fine in 1.7.3) - the iteratively parsing of the model leads to stack overflow.

from pydantic import BaseModel
from pydantic.generics import GenericModel
from enum import Enum

from typing import TypeVar, Generic

class SomeStringEnum(str, Enum):
    A = "A"
    B = "B"

T = TypeVar("T")

class SomeGenericModel(GenericModel, Generic[T]):
    some_field: T

class MyModel(BaseModel):
    some_field: SomeGenericModel[SomeStringEnum]

print(MyModel.parse_obj({"some_field": {"some_field": "A"}}))
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Hi we have the same use case and the last version broke our code,
I think this is a very common use case, maybe consider releasing a hotfix to pip?

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We will release v1.8.1 in a day or two with a fix for this. You can help by checking all the PRs related to issues since v1.8.

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bug V1 Bug related to Pydantic V1.X
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