Exception handler with Fastify leaks internals if content type is set

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Current behavior

import { Controller, Get, Header } from '@nestjs/common';

@Controller()
export class AppController {
  @Get()
  @Header('Content-Type', 'text/xml')
  get(): string {
    throw new Error();
    // return 'ok';
  }
}

Throw an error:

[1635460397235] ERROR (6802 on MacBook-Pro.fritz.box): Promise errored, but reply.sent = true was set
    reqId: "req-1"
    err: {
      "type": "FastifyError",
      "message": "Attempted to send payload of invalid type 'object'. Expected a string or Buffer.",
      "stack":
          FastifyError: Attempted to send payload of invalid type 'object'. Expected a string or Buffer.
              at onSendEnd (/Users/thomaschaaf/develop/x/x-api/node_modules/fastify/lib/reply.js:430:11)
              at onSendHook (/Users/thomaschaaf/develop/x/x-api/node_modules/fastify/lib/reply.js:390:5)
              at _Reply.Reply.send (/Users/thomaschaaf/develop/x/x-api/node_modules/fastify/lib/reply.js:193:3)
              at FastifyAdapter.reply (/Users/thomaschaaf/develop/x/x-api/node_modules/@nestjs/platform-fastify/adapters/fastify-adapter.js:46:29)
              at ExceptionsHandler.handleUnknownError (/Users/thomaschaaf/develop/x/x-api/node_modules/@nestjs/core/exceptions/base-exception-filter.js:38:24)
              at ExceptionsHandler.catch (/Users/thomaschaaf/develop/x/x-api/node_modules/@nestjs/core/exceptions/base-exception-filter.js:17:25)
              at ExceptionsHandler.next (/Users/thomaschaaf/develop/x/x-api/node_modules/@nestjs/core/exceptions/exceptions-handler.js:16:20)
              at Object.<anonymous> (/Users/thomaschaaf/develop/x/x-api/node_modules/@nestjs/core/router/router-proxy.js:13:35)
              at processTicksAndRejections (internal/process/task_queues.js:93:5)
      "name": "FastifyError",
      "code": "FST_ERR_REP_INVALID_PAYLOAD_TYPE",
      "statusCode": 500
    }

and results in a response like this:

{
  "statusCode": 500,
  "code": "FST_ERR_REP_INVALID_PAYLOAD_TYPE",
  "error": "Internal Server Error",
  "message": "Attempted to send payload of invalid type 'object'. Expected a string or Buffer."
}

Minimum reproduction code

See above

Steps to reproduce

No response

Expected behavior

Should not pass fastify error to the enduser

Package

Other package

No response

NestJS version

8.1.2

Packages versions

Node.js version

No response

In which operating systems have you tested?

macOS
Windows
Linux

Other

No response

Issue Analytics

State:
Created 2 years ago
Reactions:4
Comments:6 (4 by maintainers)

Top GitHub Comments

1reaction

kamilmysliwieccommented, Dec 23, 2021

Well, so this one is problematic. The default, built-in exception filter automatically converts all errors to a JSON-compatible format (to respond with the “Internal server error” in case it received an unexpected error it cannot recognize/classify).

Now, if you change the content type to, let’s say, application/pdf (or XML), Fastify throws an exception because the exception filter automatically tries to respond with the JSON object. However, we can’t really add checks for all possible content types (because that wasn’t the goal from the early beginning) you could potentially use in your app to the exception filter. I’m not even sure if we should classify this as a “bug”, instead, I think we should just add a warning (within the filter) that the default response format is JSON and if you want to auto-react to errors thrown from within handlers that support xml/etc you should attach a custom filter (to format the error accordingly).

0reactions

kamilmysliwieccommented, Oct 31, 2022

Let’s track this here https://github.com/nestjs/nest/pull/10474