how to handle errors in exception filters with Fastify NestJs?

Question

Im using the following code to catch error in fastify, however my error is that "response.send" is not a function:

What's the right way to send the error on my global exception filters using that structure in Fastify?

    import {
      ArgumentsHost,
      Catch,
      ExceptionFilter,
      HttpException,
      HttpStatus,
      Injectable,
    } from '@nestjs/common';
    import dotenv from 'dotenv';
    import { FastifyReply, FastifyRequest } from 'fastify';
    
    
    @Catch()
    @Injectable()
    export class HttpExceptionFilter implements ExceptionFilter {
     
      catch(exception: any, host: ArgumentsHost) {
        const context = host.switchToHttp();
        const response: FastifyReply<any> = context.getResponse<FastifyReply>();
        const request: FastifyRequest = context.getRequest<FastifyRequest>();
        let status =
          exception instanceof HttpException
            ? exception.getStatus()
            : HttpStatus.INTERNAL_SERVER_ERROR;
    
        const message =
          exception instanceof Error ? exception.message : exception.message.error;
    
        response.send({"test":"test"})
      }
    
    }

Answer 1

You should add the exception at catch decorator, ie @Catch(HttpException),and without injectable decorator. My snippet for custom http-exception-filter is like below and it works. Hope this help.

@Catch(HttpException)
export class HttpExceptionFilter<T extends HttpException> implements ExceptionFilter
    {
      catch(exception: T, host: ArgumentsHost) {
        const ctx = host.switchToHttp();
        const response: FastifyReply<any> = ctx.getResponse<FastifyReply>();
    
        const status = exception.getStatus();
        const exceptionResponse = exception.getResponse();
    
        const error =
          typeof response === 'string'
            ? { message: exceptionResponse }
            : (exceptionResponse as object);
    
        response
          .status(status)
          .send({ ...error, timestamp: new Date().toISOString() });
      }
    }