Issues that NestJS docs don't solve

OpenAPI

Hiding schema section

There is no special switch to turn off and turn on schema section module in OpenAPI implementation for NestJS. You can simply set defaultModelsExpandDepth param in swaggerOptions, while setting up SwaggerModule.

const options = new DocumentBuilder()
  .setTitle('Docs without schema section')
  .build();
const document = SwaggerModule.createDocument(app, options);
SwaggerModule.setup('api', app, document, {
  swaggerOptions: { defaultModelsExpandDepth: -1 },
});

Sorting tags and endpoints

OpenAPI allows handy grouping with tags. You just need to use @ApiTags() or @ApiOperational({ tags: ['YourTag']}) decorators. If you wish to sort tags or endpoints alphabetically, you need to pass tagsSorter and operationsSorter as option in swaggerOptions.

const options = new DocumentBuilder()
  .setTitle('Docs with sorted tags and endpoints')
  .build();
const document = SwaggerModule.createDocument(app, options);

SwaggerModule.setup('api', app, document, {
  swaggerOptions: { tagsSorter: 'alpha', operationsSorter: 'alpha' },
});

Validation

Validation of nested objects with class-validator

If you want to validate nested object in your DTO with class-validator, use @ValidateNested() decorator and specify typing with @Type() decorator.

export class Message {
  @ValidateNested()
  @Type(() => Author)
  author: Author;
}

If you need to validate array of objects, use each: true option for @ValidateNested() decorator.

export class User {
  @ValidateNested({ each: true })
  @Type(() => Message)
  messages: Message[];
}

You can also read more about it in my article.

Dependency Injection in custom validation class

If you want to create your own validation class and inject into it your dependencies, you need to:

1. Create custom validation class as official class-validator documentation says. E.g.:

@ValidatorConstraint({ name: 'userName', async: true })
@Injectable()
export class UserExists implements ValidatorConstraintInterface {
  constructor(private usersRepository: UsersRepository) {}

  async validate(value: number, arg: ValidationArguments) {
    try {
      await this.userRepository.find({id});
    } catch (e) {
      return false;
    }

    return true;
  }

  defaultMessage(args: ValidationArguments) {
    return `User doesn't exist!`;
  }
}

2. Then you must add your validation class as provider in the module, where you want to use it. E.g.:

@Module({
  imports: [
    TypeOrmModule.forFeature([
      UsersRepository
    ]),
  ],
  controllers: [UsersController],
  providers: [UserExists],
})
export class UserModule {}

3. Last but not least, you must set Nest container for class-validator library in your main.ts file:

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  useContainer(app.select(AppModule), { fallbackOnErrors: true });

  await app.listen(3000);
}

Now you can use your services and repository in custom validation classes. I don't need to say how useful this is!

You can also read more about it in my article.

TypeOrm

How to get SQL query with filled parameters?

Even it isn't NestJS related case only, but it can be useful for many developers. Many times you need to print out SQL query, to check it manually in your database. Although TypeORM provides getSql() method, it isn't handy for developers because it doesn't fill parameter placeholders. And you get something like this:

SELECT *
FROM users
WHERE id = ?
AND name = ?
ORDER BY ?

You must admit it isn't very helpful because you need to replace each ? with proper value. Here is a quick snippet, which will help you:

let [sql, params] = query.getQueryAndParameters(); 
params.forEach((value) => { 
  if (typeof value === 'string') { 
    sql = sql.replace(`?`, `"value"`); 
  } else { 
    sql = sql.replace(`?`, value); 
  } 
}); 

console.log(sql);

query variable is SelectQueryBuilder type.

If you're using Visual Studio Code as your IDE, you can try the snippet below:

"Print to console SQL query with filled params": {
  "prefix": "sqldump",
  "body": [
    "let [sql, params] = query.getQueryAndParameters(); \nparams.forEach((value) => { \n  if (typeof value === 'string') { \n    sql = sql.replace(`?`, `\"\\${value}\"`); \n  } else { \n    sql = sql.replace(`?`, value); \n  } \n}); \n\nconsole.log(sql);\n"
  ]
}