Merge target response¶

When a route already declares a response at the target code, the validation error is merged into it with anyOf instead of replacing it:

class OutOfStock(BaseModel):
    item_name: str


@app.post(
    "/items",
    responses={400: {"model": OutOfStock, "description": "Out of stock"}},
)
def create_item(item: Item) -> Item:
    return item


override_validation_error(app)

The 400 of POST /items documents anyOf: [HTTPValidationError, OutOfStock], and its description becomes Out of stock / Validation Error. At runtime nothing changes: a request that fails validation gets the validation error, and OutOfStock is for errors you raise yourself.

The merge happens within one content type. With a media_type other than application/json, a response declared under application/json is kept next to the validation error instead.

Leave the response untouched¶

With merge_target_response=False, a response the route declares at the target code is left as it is:

override_validation_error(app, merge_target_response=False)

The 400 of POST /items then documents only OutOfStock, described as Out of stock. Routes that don't declare a 400 still get the validation error.

A response declared as a $ref at the target code is always left untouched, whatever merge_target_response says.