[Bug]: Error: Cannot set headers after they are sent to the client

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

I have an endpoint in my NestJS application that responds with image instead of json:

@Get('/og/:hash')
async getOpenGraphImage(@Param('hash') hash: string, @Res() response: Response): Promise<Response<Buffer>> {
  const imageBuffer = await this.ogImageService.getImageBuffer(hash);

  return response.setHeader('Content-Type', 'image/png').send(imageBuffer);
}

But whenever I try to hit this endpoint I see the following error in the terminal:

This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason:
Error: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:371:5)
    at ServerResponse.setHeader (node:_http_outgoing:576:11)
    at ServerResponse.header (/home/goodwin/flaut-nestjs/node_modules/express/lib/response.js:776:10)
    at ServerResponse.send (/home/goodwin/flaut-nestjs/node_modules/express/lib/response.js:170:12)
    at ServerResponse.json (/home/goodwin/flaut-nestjs/node_modules/express/lib/response.js:267:15)
    at ExpressAdapter.reply (/home/goodwin/flaut-nestjs/node_modules/@nestjs/platform-express/adapters/express-adapter.js:36:57)
    at ExceptionsHandler.handleUnknownError (/home/goodwin/flaut-nestjs/node_modules/@nestjs/core/exceptions/base-exception-filter.js:38:24)
    at ExceptionsHandler.catch (/home/goodwin/flaut-nestjs/node_modules/@nestjs/core/exceptions/base-exception-filter.js:17:25)
    at ExceptionsHandler.next (/home/goodwin/flaut-nestjs/node_modules/@nestjs/core/exceptions/exceptions-handler.js:16:20)
    at /home/goodwin/flaut-nestjs/node_modules/@nestjs/core/router/router-proxy.js:13:35

Minimum reproduction code

Private repo with copyrighted codebase

Steps to reproduce

No response

Expected behavior

Ogma should verify if the response has already been sent by checking out the value of res.headersSent

Package(s) version

• @ogma/nestjs-module: 3.1.1
• @ogma/platform-express: 3.0.1

Node.js version

16.13.2

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[abriginets]

Oh, I didn’t mention in the docs that StreamableFile can accept not only a stream but also a buffer. I was able to achieve full compatibility with Ogma for both simple and more complex endpoints:

@Get('/location/code/:code/width/:width/height/:height/extension/:extension')
@Header('Content-Disposition', 'inline')
async getLocationImage(
  @Param('code') code: string,
  @Param('width', new ParseIntPipe()) width: number,
  @Param('height', new ParseIntPipe()) height: number,
  @Param('extension', new LocationImageExtensionValidationPipe()) extension: LocationImageFormatEnum,
  @Res({ passthrough: true }) response: Response,
): Promise<StreamableFile> {
  const imageBuffer = await this.imageLocationService.getLocationImage(code, width, height, extension);

  response.setHeader('Content-Type', mime.contentType(extension) as string);

  return new StreamableFile(imageBuffer);
}

@Get('/og/:hash')
@Header('Content-Disposition', 'inline')
@Header('Content-Type', 'image/png')
async getOpenGraphImage(@Param('hash') hash: string): Promise<StreamableFile> {
  const imageBuffer = await this.ogImageService.getImageBuffer(hash);

  return new StreamableFile(imageBuffer);
}

To summarize:

• @Header('Content-Type', 'image/png') decorator can be used to set image format declarative way
• To set image type imperatively response.setHeader('Content-Type', imageFormat); notation can be used for cases when image format depends on request parameters, but @Res decorator must be used with passthrough option set to true.
• Also I’m using @Header('Content-Disposition', 'inline') to disable “download the file” behavior in the browser because Nest appends Content-Disposition: null header by default when StreamableFile is returned.

All of the above helped me to achieve the absolute same behavior decleratively compared to what I had before imperatively. Thank you!

[jmcdo29]

You can also pass a second parameter to the StreamableFile’s constructor for setting content dispositions and such. Glad you were able to make it work. I’ll go ahead and close out the issue, as it’s something at Nest’s level, but I’ll keep an eye on this if you need anything else