Traceback
File {frame_filename}, line {frame_lineno}, in {frame_name} {collapse_button}
{lineno}. {line}
""" CENTER_LINE = """{lineno}. {line}
""" class ServerErrorMiddleware: """ Handles returning 500 responses when a server error occurs. If 'debug' is set, then traceback responses will be returned, otherwise the designated 'handler' will be called. This middleware class should generally be used to wrap *everything* else up, so that unhandled exceptions anywhere in the stack always result in an appropriate 500 response. """ def __init__( self, app: ASGIApp, handler: typing.Callable[[Request, Exception], typing.Any] | None = None, debug: bool = False, ) -> None: self.app = app self.handler = handler self.debug = debug async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None: if scope["type"] != "http": await self.app(scope, receive, send) return response_started = False async def _send(message: Message) -> None: nonlocal response_started, send if message["type"] == "http.response.start": response_started = True await send(message) try: await self.app(scope, receive, _send) except Exception as exc: request = Request(scope) if self.debug: # In debug mode, return traceback responses. response = self.debug_response(request, exc) elif self.handler is None: # Use our default 500 error handler. response = self.error_response(request, exc) else: # Use an installed 500 error handler. if is_async_callable(self.handler): response = await self.handler(request, exc) else: response = await run_in_threadpool(self.handler, request, exc) if not response_started: await response(scope, receive, send) # We always continue to raise the exception. # This allows servers to log the error, or allows test clients # to optionally raise the error within the test case. raise exc def format_line( self, index: int, line: str, frame_lineno: int, frame_index: int ) -> str: values = { # HTML escape - line could contain < or > "line": html.escape(line).replace(" ", " "), "lineno": (frame_lineno - frame_index) + index, } if index != frame_index: return LINE.format(**values) return CENTER_LINE.format(**values) def generate_frame_html(self, frame: inspect.FrameInfo, is_collapsed: bool) -> str: code_context = "".join( self.format_line( index, line, frame.lineno, frame.index, # type: ignore[arg-type] ) for index, line in enumerate(frame.code_context or []) ) values = { # HTML escape - filename could contain < or >, especially if it's a virtual # file e.g.