Docs for "Separate OpenAPI schemas for input and output" should be updated because of a Pydantic change

[RomeoDespres]

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Example Code

# This code is taken from the documentation but is incomplete.
# See fix in the description

from pydantic import BaseModel


class Item(BaseModel):   
    name: str
    description: str | None = None

Description

In the docs on separate OpenAPI schemas for input and output (here) it is implied that using pydantic v2 will by default enable the separate schema behavior.

However since pydantic v2.4.0, defaults values are serialized as non-required by default (see release notes).

To enable the schema separation behavior, the following configuration must now be added:

from pydantic import BaseModel, ConfigDict


class Item(BaseModel):
    model_config = ConfigDict(json_schema_serialization_defaults_required=True)

    name: str
    description: str | None = None

Shouldn't this be mentioned in FastAPI docs? I've just spent half a day trying to understand why my schemas were not separate for input and output, thought others may face that too

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.103.2

Pydantic Version

2.4.2

Python Version

3.11.1

Additional Context

No response

[CroMarmot]

fastapi 0.111.0
pydantic 2.7.1
python3 3.10.12

maybe relative: hey-api/openapi-ts#597