First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
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• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
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Example Code

from fastapi import FastAPI
from pydantic import BaseModel
from fastapi import Request


class ResponseInfo(BaseModel):
    status: str | None = None
    entry_id: int


app = FastAPI()

@app.post("/info", response_model=ResponseInfo)
async def read_item(request: Request):
    return ResponseInfo(entry_id=10)

Description

After running server i expect to see response model to have optional status, but swagger show it as required.

I checked app.openapi() it returns ... 'required': ['status', 'entry_id']
And check pydantic:
{'properties': {'status': {'anyOf': [{'type': 'string'}, {'type': 'null'}], 'default': None, 'title': 'Status'}, 'entry_id': {'title': 'Entry Id', 'type': 'integer'}}, 'required': ['entry_id'], 'title': 'ResponseInfo', 'type': 'object'}

This takes place only in response_model; in request works as expected

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.101.0

Pydantic Version

2.1.1

Python Version

3.11.0

Additional Context

No response