Update Version 2.5.3 to 2.6.0 error -> LookupError: Could not find a ref for #/components/schemas/xpto . Maybe you tried to call resolve_ref_schema from within a recursive model?

[MatheusVp2]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

After updating from pydantic 2.5.3 > 2.6.0, updating in my project, it broke all tests, with the problem of LookupError: Could not find a ref for #/components/schemas/xpto . Maybe you tried to call resolve_ref_schema from within a recursive model?

Example Code

import typing
from enum import Enum

from fastapi import FastAPI
from fastapi.openapi.utils import get_openapi
from pydantic import BaseModel, Field


class AllowedValues(str, Enum):
    VAL1 = 'Val1'
    VAL2 = 'Val2'


class ModelA(BaseModel):
    # Removing the max_length from the Field definition will make the code work
    modelA_1: AllowedValues = Field(..., max_length=60)


class ModelB(ModelA):
    modelB_1: typing.List[ModelA]


class ModelC(BaseModel):
    # Removing modelC_1 or modelC_2 and keeping only one of them will make the code work
    modelC_1: ModelB
    modelC_2: ModelB


class ModelD(BaseModel):
    modelD_1: typing.List[ModelC]


app = FastAPI(version='1.0.0')


@app.post('/route1', response_model=ModelD)
async def route1():
    raise NotImplementedError


schema = get_openapi(
    title='test',
    servers=[{"url": "https://test.com", "description": "desc"}],
    description='description',
    version='1.0.0',
    routes=app.routes)
print(schema)

No response

Python, Pydantic & OS Version

pydantic version: 2.6.0
        pydantic-core version: 2.16.1
          pydantic-core build: profile=release pgo=true
                 install path: /home/myuser/.pyenv/versions/3.9.14/envs/project/lib/python3.9/site-packages/pydantic
               python version: 3.9.14 (main, Dec  9 2022, 17:08:14)  [GCC 9.4.0]
                     platform: Linux-5.15.0-92-generic-x86_64-with-glibc2.31
             related packages: typing_extensions-4.9.0 fastapi-0.109.0
                       commit: unknown

[sydney-runkle]

@MatheusVp2,

Could you please provide a code snippet from which we can reproduce this error? Thanks!

[MatheusVp2]

@sydney-runkle

I managed to debug the application here and found that when I call the function, get_openapi from from fastapi.openapi.utils import get_openapi, it breaks and throws the error

[Kludex]

We need a minimal reproducible example that we can run. Would you mind providing that? 🙏

[MatheusVp2]

@Kludex @sydney-runkle
Added the minimum code example there to simulate the error. Emphasizing that it works in version 2.5.3.

[Kludex]

I can reproduce the issue on 2.6.

[dmontagu]

Somewhat simplified pure-pydantic reproduction of the issue:

import typing
from enum import Enum

from pydantic import BaseModel, Field


class AllowedValues(str, Enum):
    VAL1 = 'Val1'
    VAL2 = 'Val2'


class ModelA(BaseModel):
    # Removing the max_length from the Field definition will make the code work
    modelA_1: AllowedValues = Field(..., max_length=60)


class ModelB(ModelA):
    modelB_1: typing.List[ModelA]


class ModelC(BaseModel):
    modelC_1: ModelB


class Model(BaseModel):
    b: ModelB
    c: ModelC


Model.model_json_schema()

I had feared this was also introduced by #8526 but that doesn't seem to be the case.

[sydney-runkle]

I've traced the source of this issue to here: b2aa36a