venv/lib/python3.11/site-packages/starlette/middleware/exceptions.py

from __future__ import annotations

import typing

from starlette._exception_handler import (
    ExceptionHandlers,
    StatusHandlers,
    wrap_app_handling_exceptions,
)
from starlette.exceptions import HTTPException, WebSocketException
from starlette.requests import Request
from starlette.responses import PlainTextResponse, Response
from starlette.types import ASGIApp, Receive, Scope, Send
from starlette.websockets import WebSocket


class ExceptionMiddleware:
    def __init__(
        self,
        app: ASGIApp,
        handlers: typing.Mapping[typing.Any, typing.Callable[[Request, Exception], Response]] | None = None,
        debug: bool = False,
    ) -> None:
        self.app = app
        self.debug = debug  # TODO: We ought to handle 404 cases if debug is set.
        self._status_handlers: StatusHandlers = {}
        self._exception_handlers: ExceptionHandlers = {
            HTTPException: self.http_exception,
            WebSocketException: self.websocket_exception,
        }
        if handlers is not None:  # pragma: no branch
            for key, value in handlers.items():
                self.add_exception_handler(key, value)

    def add_exception_handler(
        self,
        exc_class_or_status_code: int | type[Exception],
        handler: typing.Callable[[Request, Exception], Response],
    ) -> None:
        if isinstance(exc_class_or_status_code, int):
            self._status_handlers[exc_class_or_status_code] = handler
        else:
            assert issubclass(exc_class_or_status_code, Exception)
            self._exception_handlers[exc_class_or_status_code] = handler

    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
        if scope["type"] not in ("http", "websocket"):
            await self.app(scope, receive, send)
            return

        scope["starlette.exception_handlers"] = (
            self._exception_handlers,
            self._status_handlers,
        )

        conn: Request | WebSocket
        if scope["type"] == "http":
            conn = Request(scope, receive, send)
        else:
            conn = WebSocket(scope, receive, send)

        await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)

    def http_exception(self, request: Request, exc: Exception) -> Response:
        assert isinstance(exc, HTTPException)
        if exc.status_code in {204, 304}:
            return Response(status_code=exc.status_code, headers=exc.headers)
        return PlainTextResponse(exc.detail, status_code=exc.status_code, headers=exc.headers)

    async def websocket_exception(self, websocket: WebSocket, exc: Exception) -> None:
        assert isinstance(exc, WebSocketException)
        await websocket.close(code=exc.code, reason=exc.reason)  # pragma: no cover