No 'response_model_' routing option available to pass 'serialize_as_any=True' to pydantic

[ostefano]

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.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• 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.
• I already checked if it is not related to FastAPI but to ReDoc.

Commit to Help

• I commit to help with one of those options 👆

Example Code

@self.get(
    "/method",
    response_model_serialize_as_any=True,
)
async def get_method(

Description

When specifying response model options there is no way to pass the serialize_as_any option to pydantic.

Note: it is possible to pass other pydantic options (e.g., by_alias=True by using response_model_by_alias=True)
I guess this is because this options has been added in pydantic 2.7.1 which has been released just a few weeks ago.

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.110.0

Pydantic Version

2.7.1

Python Version

Python 3.12.3

Additional Context

No response

[MrPranav101]

came here to say the same :) Please support this :)

[lean-zone]

FastAPI developers, please support this as soon as possible.

[florianabel]

Any news here already?

[YuriiMotov]

I believe this shouldn't be added to FastAPI.
If you want to bypass the response validation, just return JSONResponse directly from the endpoint.

from fastapi.responses import JSONResponse
from pydantic import BaseModel
from fastapi import FastAPI

app = FastAPI()

class User(BaseModel):
    name: str

class UserLogin(User):
    password: str

@app.get("/", response_model=User)
async def get_user():
    user = UserLogin(name="John Doe", password="secret123")
    return JSONResponse(content=user.model_dump())