RequestValidationError is **not** a sub-class of Pydantic's ValidationError

[Kludex]

Discussed in #10421

^{Originally posted by valentinoli October 10, 2023}

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Example Code

@app.exception_handler(ValidationError)
async def validation_exception_handler(request: Request, exc: ValidationError):
    return PlainTextResponse(
        str(exc), status_code=status.HTTP_500_INTERNAL_SERVER_ERROR
    )

Description

I was trying to handle both RequestValidationError and ValidationError by writing a custom handler for ValidationError but that doesn't work.

The docs state that

RequestValidationError is a sub-class of Pydantic's ValidationError

However, looking at FastAPI source code reveals that this is not the case.

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.101.0

Pydantic Version

2.1.1

Python Version

3.11.3

Additional Context

No response

[Kludex]

The documentation needs to be fixed. The RequestValidationError was a subclass of ValidationError before 0.100.0 - it's not the case anymore.

[sanzoghenzo]

Duplicate of #10424 😉

[Kludex]

Ah. I forgot. Thanks.