class-validator doesn't appear to do anything in NestJS application - nestjs

Question

I'm setting up a new NestJS application, and I've just added class-validator in order to validate controller input, but it seems to be completely ignored. This is the DTO:
import {IsString} from 'class-validator';
export class CreateCompanyDto {
#IsString()
name: string | undefined;
}
This is the controller:
import {
Body,
Controller,
InternalServerErrorException,
Post,
Request,
UseGuards, ValidationPipe
} from '#nestjs/common';
import * as admin from 'firebase-admin';
import {User} from 'firebase';
import {AuthGuard} from '../auth/auth.guard';
import {CurrentUser} from '../auth/current-user.decorator';
import {CreateCompanyDto} from './dto/create-company.dto';
#Controller('vendor')
export class VendorController {
#Post()
#UseGuards(AuthGuard)
async create(#CurrentUser() user: User, #Request() req: any, #Body(new ValidationPipe({ transform: true })) company: CreateCompanyDto) {
console.log(JSON.stringify(company));
throw new InternalServerErrorException('meh?');
// irrelevant code
}
}
I would expect the code to throw a validation error and never hit the method itself, but instead it runs into the exception, and the object is logged exactly as it came in.
package.json:
{
"name": "functions",
"scripts": {
"lint": "tslint --project tsconfig.json",
"prebuild": "(cd src && rm settings.json && ln -s ../configs/prod.json settings.json)",
"build": "tsc",
"prebuild:dev": "(cd src && rm settings.json && ln -s ../configs/dev.json settings.json)",
"build:dev": "tsc",
"serve": "concurrently \"npm run build:dev -- --watch\" \"firebase emulators:start --only functions\"",
"shell": "npm run build && firebase functions:shell",
"start": "npm run shell",
"deploy": "firebase deploy --only functions",
"logs": "firebase functions:log"
},
"engines": {
"node": "8"
},
"main": "lib/functions/src/index.js",
"dependencies": {
"#elastic/elasticsearch": "^7.6.0",
"#nestjs/common": "^6.11.11",
"#nestjs/core": "^6.11.11",
"#nestjs/platform-express": "^6.11.11",
"#types/airtable": "^0.5.7",
"#types/nodemailer": "^6.4.0",
"airtable": "^0.8.1",
"class-transformer": "^0.2.3",
"class-validator": "^0.11.0",
"cors": "^2.8.5",
"express": "^4.17.1",
"firebase": "^7.10.0",
"firebase-admin": "^8.9.2",
"firebase-functions": "^3.3.0",
"nodemailer": "^6.4.4",
"reflect-metadata": "^0.1.13",
"rxjs": "^6.5.4",
"slugify": "^1.4.0"
},
"devDependencies": {
"concurrently": "^5.1.0",
"tslint": "^6.0.0",
"typescript": "~3.7.5"
},
"private": true
}
What am I missing here?
Update
I did a little debugging, and I can tell where it's going wrong, even though I still don't know why.
In the ValidationPipe.transform method, it returns the raw input, because metatype is undefined:
async transform(value, metadata) {
const { metatype } = metadata;
if (!metatype || !this.toValidate(metadata)) {
return value;
}
// ...
}

Answer 1

in main.ts add app.useGlobalPipes(new ValidationPipe());:
import { ValidationPipe } from '#nestjs/common';
import { NestFactory } from '#nestjs/core';
import { AppModule } from './app.module';
async function bootstrap() {
const app = await NestFactory.create(AppModule);
app.enableCors();
app.useGlobalPipes(new ValidationPipe());
await app.listen(process.env.PORT || 3000);
}
bootstrap();

Answer 2

Ok, the debugging gave me enough info to find the issue on Google, where I found this Github issue: https://github.com/nestjs/nest/issues/690
You need to enable "emitDecoratorMetadata": true in your tsconfig.json file for this to work.

Answer 3

In my case the validations did not work as I did not have the class-transformer dependency in my application. Hope this helps someone.
You need both class-validator and class-transformer
$ npm i --save class-validator class-transformer