nest.js exception filtering

another-exception-filter-example.ts

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

@Catch()
export class GlobalExceptionsFilter implements ExceptionFilter {
    public catch(exception: any, host: ArgumentsHost): void {
        const ctx = host.switchToHttp();
        const response: Response = ctx.getResponse<Response>();
        const clazz = exception.constructor.name;

        if (process.env.DEBUG) {
            console.error(`GlobalExceptionsFilter.catch(): ${JSON.stringify(exception)}`);
            console.error(`GlobalExceptionsFilter.catch(): class name = ${clazz}`);
        }

        if (clazz === 'UnauthorizedException') {
            response.sendStatus(401);
        } else if (clazz === 'BadRequestException') {
            response.sendStatus(400);
        } else if (clazz === 'ResourceNotFoundException') {
            response.sendStatus(exception.status);
        } else if (clazz === 'ResourceForbiddenException') {
            response.sendStatus(exception.status);
        } else if (clazz === 'EntityNotFoundError') {
            response.sendStatus(HttpStatus.NOT_FOUND);
        } else if (clazz === 'ResourceAlreadyExistsException') {
            response.sendStatus(exception.status);
        } else if (clazz === 'QueryFailedError') {
            if (exception.message.indexOf('duplicate key') >= -1) {
                response.sendStatus(HttpStatus.CONFLICT);
            }
        } else if (exception.status) {
            response.sendStatus(exception.status);
        } else {
            response.sendStatus(500);
        }
    }
}

GlobalExceptionHandler.ts

import { ArgumentsHost, Catch, ConflictException, ExceptionFilter } from '@nestjs/common';

@Catch()
export class GlobalExceptionsFilter implements ExceptionFilter {
    public catch(exception: any, host: ArgumentsHost): void {
        // const log = {
        //     date: new Date(),
        //     source: request.ip,
        //     url: request.url,
        //     method: request.method,
        //     headers: request.headers,
        //     body: JSON.stringify(request.body).slice(0, 1000),
        //     exception: exception.message,
        //     status: exception.status,
        //     clazz: clazz
        // };

        // console.log(log);
        // if (process.env.DEBUG) {
        //     console.error(`GlobalExceptionsFilter.catch()`, log);
        // }

        console.log(exception.code);
        if (exception.code === 'P2002') {
            throw new ConflictException();
        }
    }
}

main.ts

require('dotenv').config({ path: `.env.${process.env.ENVIRONMENT || 'local'}` });

import { INestApplication, ValidationPipe } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';
import { GraphQLSchemaFactory } from '@nestjs/graphql';
import * as fs from 'fs';
import { printSchema } from 'graphql/utilities';
import { GlobalExceptionsFilter } from './Lib/GlobalExceptionsFilter';
import { AppModule } from './module';
import { RESOLVERS } from './resolvers';

export let app: INestApplication = null;

async function bootstrap() {
    app = await NestFactory.create(AppModule, {
        snapshot: true
    });
    app.useGlobalFilters(new GlobalExceptionsFilter());
    
    await app.listen(3000);

    const gqlSchemaFactory = app.get(GraphQLSchemaFactory);
    const schema = await gqlSchemaFactory.create(RESOLVERS);
    fs.writeFileSync('schema.graphql', printSchema(schema));
}

void bootstrap();