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.