Custom RequestValidationError but Swagger not update the schema

[bfss]

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• I already checked if it is not related to FastAPI but to Swagger UI.
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Example Code

@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request, exc):
    errors = exc.errors()
    custom_error = []
    for error in errors:
        custom_error.append(error['msg'])
    return JSONResponse(status_code=422, content=jsonable_encoder({'detail': custom_error}))

Description

After I custom the RequestValidationError above, the swagger's schema is still the original one.

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.79.0

Python Version

3.9.13

Additional Context

No response

[iudeen]

Not sure if adding it this way changes OpenAPI doc.

[JarroVGIT]

@iudeen is correct, adding a handler does not automagically add that to the generated openapi.json. You would have to add those to the endpoints themselves in order for them to show up in the spec, otherwise it will use the default definition:

validation_error_definition = {
    "title": "ValidationError",
    "type": "object",
    "properties": {
        "loc": {
            "title": "Location",
            "type": "array",
            "items": {"anyOf": [{"type": "string"}, {"type": "integer"}]},
        },
        "msg": {"title": "Message", "type": "string"},
        "type": {"title": "Error Type", "type": "string"},
    },
    "required": ["loc", "msg", "type"],
}

validation_error_response_definition = {
    "title": "HTTPValidationError",
    "type": "object",
    "properties": {
        "detail": {
            "title": "Detail",
            "type": "array",
            "items": {"$ref": REF_PREFIX + "ValidationError"},
        }
    },
}

[bfss]

@JarroVGIT Thanks, but how could I add them to endpoints?

[JarroVGIT]

It’s described here in the docs . You can add a 422 response in the responses parameter of the decorator and that will override the default.

[bfss]

@JarroVGIT Thanks again! I'll close this issue~