Custom RequestValidationError Handling Overwritten in stac-fastapi

In our FastAPI application using stac-fastapi, we encountered an issue where the RequestValidationError handling gets overwritten if it is registered before the creation of StacApi.

Sample Code Demonstrating the Error:

from fastapi import FastAPI, Request
from stac_fastapi.api.app import StacApi
from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse
from stac_fastapi.types.config import ApiSettings
from stac_fastapi.pgstac.core import CoreCrudClient
from stac_fastapi.extensions.core import (
    FieldsExtension,
    ContextExtension,
    QueryExtension,
    SortExtension,
)

app = FastAPI()

@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request, exc):
    return JSONResponse(
        status_code=400,
        content={"customerrordetail": exc.errors(), "body": exc.body},
    )

extensions = [FieldsExtension(), ContextExtension(), QueryExtension(), SortExtension()]

PCClient = CoreCrudClient()
settings = ApiSettings()

# First initialization of StacApi
stac_api = StacApi(
    app=app,
    settings=settings,
    extensions=extensions,
    client=PCClient,
    exceptions={},
    middlewares=[],
)

# Test route to trigger RequestValidationError
@app.post("/items/")
async def create_item(item: dict):
    return item

Steps to Reproduce:

uvicorn main:app --reload
curl -X POST "http://127.0.0.1:8000/items/" -H "Content-Type: application/json"

Expected Behavior: {"customerrordetail":[{"type":"missing","loc":["body"],"msg":"Field required","input":null}],"body":null}

Actual Behavior: {"code":"RequestValidationError","description":"[{'type': 'missing', 'loc': ('body',), 'msg': 'Field required', 'input': None}]"}

Workaround: To avoid the issue, the RequestValidationError handling must be registered after StacApi creation

stac-utils / stac-fastapi

Custom RequestValidationError Handling Overwritten in stac-fastapi #720