Change Unexpected field error message in NestJS

Question

I have this code

@Post('files')
@UseInterceptors(FilesInterceptor("files", 5))
async uploadFiles () {
...
}

When I try to upload more files, I get this error “Unexpected field”, is there any way I can change this error to my custom one?

Answer 1

You can use Exception filters from NestJS like explained in the NestJS doc : Exception Filter NestJS doc

create file like this http-exception.filter.ts

import { ExceptionFilter, Catch, ArgumentsHost, HttpException } from '@nestjs/common';
import { Request, Response } from 'express';

@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    const request = ctx.getRequest<Request>();
    const status = exception.getStatus();

    response
      .status(status)
      .json({
        statusCode: status,
        timestamp: new Date().toISOString(),
        path: request.url,
      });
  }
} 

and use it like this in the controller

 @UseFilters(new HttpExceptionFilter())
 @UseInterceptors(FilesInterceptor('files', 5)

then you can custom the logic of the filter to add your messages.