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python.fastapi.exception_handler

Stability Medium

Detects FastAPI apps without proper exception handlers.

Why It Matters

Missing exception handlers:

500 errors exposed — Internal details leak to users
Poor UX — Generic error messages confuse users
No logging — Errors go untracked

Example

# ❌ Before (no exception handler)
app = FastAPI()

@app.get("/users/{id}")
async def get_user(id: int):
    return await db.get_user(id)  # Unhandled errors!

# ✅ After (with exception handlers)
from fastapi import Request
from fastapi.responses import JSONResponse

@app.exception_handler(Exception)
async def general_exception_handler(request: Request, exc: Exception):
    logger.error("Unhandled error", exc_info=exc)
    return JSONResponse(
        status_code=500,
        content={"detail": "Internal server error"}
    )

@app.exception_handler(ValueError)
async def value_error_handler(request: Request, exc: ValueError):
    return JSONResponse(
        status_code=400,
        content={"detail": str(exc)}
    )

What Unfault Detects

Missing @app.exception_handler
No fallback exception handler
Unstructured error responses

python.bare_except