1, catch exception and rewrite response

def register_exception(app)
    @app.exception_handler(ValidationError)
    async def db_validation_exception_handle(request: Request, exc: ValidationError):

        exc_str = '|'.join(exc.args)
        content = {'code': 0, 'msg': exc_str, 'data': None}
        return JSONResponse(content=content, status_code=status.HTTP_422_UNPROCESSABLE_ENTITY)

2, router, api

class ValidatorError(BaseModel):
    code: int = 0
    msg: str = ''
    data: Any = None

error_response = {
    ...
    422: {
        'model': ValidatorError,
        'description': '参数验证错误的返回值 data=null',
    }
}

@router.get('', response_model=YourSchema, status_code=YourCode, responses=error_response)
def func():
    ...

@panla
Thank you. I think your idea can disable default 422 doc and left custom 422 response. But I wanna remove 422 response. My interfaces only support 200 http code, no 422.

My solution is inheriting FastAPI class and rewrite openapi method.

I want disable 200 http code, because my api never return this code, is a post request.

@DionVitor what do you mean ? Regardless of the method you need to send an http status code back

@DionVitor what do you mean ? Regardless of the method you need to send an http status code back

Yes, but a post endpoint don't need 200 in my swagger. The solution, customize the openapi dict.

@DionVitor what do you mean ? Regardless of the method you need to send an http status code back
Yes, but a post endpoint don't need 200 in my swagger. The solution, customize the openapi dict.

The purpose of the swagger api definition is to include all the possible responses for an endpoint

@DionVitor what do you mean ? Regardless of the method you need to send an http status code back

Yes, but a post endpoint don't need 200 in my swagger. The solution, customize the openapi dict.

The purpose of the swagger api definition is to include all the possible responses for an endpoint

Exactly!! 200 status it's not possible in my post endpoint.

@DionVitor what do you mean ? Regardless of the method you need to send an http status code back

Yes, but a post endpoint don't need 200 in my swagger. The solution, customize the openapi dict.

The purpose of the swagger api definition is to include all the possible responses for an endpoint

Exactly!! 200 status it's not possible in my post endpoint.

If your endpoint returns a diffferent code you can configure your response code with response_code=<YOUR_CODE>. But by default any operation should return a valid HTTP code to let the client know how to close the communication

https://restfulapi.net/http-status-codes/#:~:text=It%20indicates%20that%20the%20REST,should%20include%20a%20response%20body.

@kounelios13 I think you misunderstood what @DionVitor meant. I have probably a similar problem. I need to return the validation error with a different status code, but 422 is still in the OpenAPI if I override the ValidationError in FastAPI exception_handlers. Any tips how to remove the entry for 422 in the OpenAPI?

My newest solution:

app = FastAPI()

def custom_openapi():
    if not app.openapi_schema:
        app.openapi_schema = get_openapi(
            title=app.title,
            version=app.version,
            openapi_version=app.openapi_version,
            description=app.description,
            terms_of_service=app.terms_of_service,
            contact=app.contact,
            license_info=app.license_info,
            routes=app.routes,
            tags=app.openapi_tags,
            servers=app.servers,
        )
        for _, method_item in app.openapi_schema.get('paths').items():
            for _, param in method_item.items():
                responses = param.get('responses')
                # remove 422 response, also can remove other status code
                if '422' in responses:
                    del responses['422']
    return app.openapi_schema

app.openapi = custom_openapi

Hope this is useful. @vanntile @kounelios13

thank you

Thanks for the help and discussion all! ☕

I made a decorator and decorate the openapi method in runtime. Please note, I only remove the 422 response if the schema ends with HTTPValidationError so it won't remove my custom 422 errors.

from typing import Callable


def customize_openapi(func: Callable[..., dict]) -> Callable[..., dict]:
    """Customize OpenAPI schema."""

    def wrapper(*args, **kwargs) -> dict:
        """Wrapper."""
        res = func(*args, **kwargs)
        for _, method_item in res.get("paths", {}).items():
            for _, param in method_item.items():
                responses = param.get("responses")
                # remove default 422 - the default 422 schema is HTTPValidationError
                if "422" in responses and responses["422"]["content"][
                    "application/json"
                ]["schema"]["$ref"].endswith("HTTPValidationError"):
                    del responses["422"]
        return res

    return wrapper

Usage:

# Create the application
app = FastAPI()
app.openapi = customize_openapi(app.openapi)

Thinking that it should be an option to turn off the default 422 response. @tiangolo What do you think about this? There are cases in an API Request that there will be no scenario that returns a 422 response if your route controller is correctly setup.

What others say?

I use

app = FastAPI(
    responses={'default': {'description': 'Error response', 'content': {'application/json': {'example': {'detail': 'Error message'}}}}},
)