Handling custom error responses in FastAPI with global exception handlers
I've looked through the documentation and I'm still confused about I'm working on a FastAPI application (version 0.68.0) where I need to implement custom error handling for certain exceptions to return user-friendly error messages. I've created a global exception handler using the `exception_handler` decorator, but I'm running into issues where the response format is not what I expected, especially for validation errors. Here’s my current implementation of the exception handler: ```python from fastapi import FastAPI, Request, HTTPException from fastapi.responses import JSONResponse app = FastAPI() @app.exception_handler(HTTPException) async def http_exception_handler(request: Request, exc: HTTPException) -> JSONResponse: return JSONResponse( status_code=exc.status_code, content={ "detail": exc.detail, "path": request.url.path, "method": request.method } ) ``` When I raise an `HTTPException`, like so: ```python @app.get("/items/{item_id}") async def read_item(item_id: int): if item_id not in range(1, 10): # Simulating an invalid item raise HTTPException(status_code=404, detail="Item not found") return {"item_id": item_id} ``` It correctly returns a JSON response formatted as expected. However, when I run into a validation error due to a query parameter not being convertible to an integer, FastAPI's built-in validation error handler takes over, and I receive a response that looks like this: ```json { "detail": [ { "loc": [ "query", "item_id" ], "msg": "value is not a valid integer", "type": "value_error.integer" } ] } ``` I want to catch this validation error using my global handler and return a more user-friendly message instead. I've tried adding another exception handler for `RequestValidationError`, but it seems like the first one is not being called. Here’s what I attempted: ```python from fastapi.exceptions import RequestValidationError @app.exception_handler(RequestValidationError) async def validation_exception_handler(request: Request, exc: RequestValidationError) -> JSONResponse: return JSONResponse( status_code=422, content={ "detail": "Invalid input provided, please check your parameters." } ) ``` After implementing this, I still get the default error response instead of my custom one. Is there something I'm missing in the setup or a specific order in which these handlers should be defined? Any help would be appreciated! This is part of a larger web app I'm building. Has anyone else encountered this?