Why does the framework raise a 500 instead of a 400

[trashdid]

I have this route that I am building with query parameters, but there is are difference services that will be invoked based on the query parameter selected. I have it functioning correctly, but when conflicting query parameters are used, the pydantic model raises a value error, but litestar returns a 500 instead of 400. for context, this is what the controller function looks like:

    @get(
        operation_id="GetDataByQueryParameters",
        path="/data",
        media_type=MediaType.JSON,
        status_code=status_codes.HTTP_200_OK,
        dependencies={"filters": Provide(DataQuery, sync_to_thread=False)},
        raises=[ValidationException],
    )
    async def get_data(
        self,
        data_service: DataService,
        filters: DataQuery
    ) -> list[Data]:
        if filters.has_user_id:
            return await data_service.get_data(
                user_id=filters.user_id,
            )
        else:
            return await data_service.get_data_by_source(
                source=filters.source
            )

The Pydantic model looks like this:

class DataQuery(BaseModel):
    source: Annotated[
        str | None,
        Parameter(description="Source", examples=[Example(value="500MNY")]),
    ] = None
    user_id: Annotated[
        str | None,
        Parameter(description="User Id", examples=[Example(value="DS2943")]),
    ] = None

    @property
    def has_source(self) -> bool:
        return self.source is not None

    @property
    def has_user_id(self) -> bool:
        return self.user_id is not None

    @model_validator(mode="after")
    def validate_exclusivity(self) -> "DataQuery":
        if self.has_source and self.has_user_id:
            raise ValueError("Query Parameters cannot include both Source and User Id")
        return self

    @field_validator("user_id", mode="before")
    @classmethod
    def lower_case_user_id(cls, value:str ) -> str | None:
        if isinstance(value, str):
            return value.lower()
        else:
            return None

My issue is that the Value error is raised, but it is just mapped as 500, I would like to find a way to have it return a 400 Bad Request Error instead.

Any help would be greatly appreciated.

[provinzkraut]

Because the ValueError is just a regular exception. Litestar doesn't know about it. How could Litestar infer that this ValueError has to do with input data validation and should map to a 400 response?

You can either raise ValidationError, raise a ClientError directly, or create your own exception class and register an error handler for it.

[trashdid]

I had the same issue occur when I was using a validation error, but I didn't try a client error. I will try that and see if that fixes it. Otherwise I will try the custom exception approach. Thank you for the insight.