How to handle TypeORM entity field unique validation error in NestJS? - typeorm

Question

I've set a custom unique validator decorator on my TypeORM entity field email. NestJS has dependency injection, but the service is not injected.
The error is:
TypeError: Cannot read property 'findByEmail' of undefined
Any help on implementing a custom email validator?
user.entity.ts:
#Column()
#Validate(CustomEmail, {
message: "Title is too short or long!"
})
#IsEmail()
email: string;
My CustomEmail validator is
import {ValidatorConstraint, ValidatorConstraintInterface,
ValidationArguments} from "class-validator";
import {UserService} from "./user.service";
#ValidatorConstraint({ name: "customText", async: true })
export class CustomEmail implements ValidatorConstraintInterface {
constructor(private userService: UserService) {}
async validate(text: string, args: ValidationArguments) {
const user = await this.userService.findByEmail(text);
return !user;
}
defaultMessage(args: ValidationArguments) {
return "Text ($value) is too short or too long!";
}
}
I know I could set unique in the Column options
#Column({
unique: true
})
but this throws a mysql error and the ExceptionsHandler that crashes my app, so I can't handle it myself...
Thankx!

Answer 1

I can propose 2 different approaches here, the first one catches the constraint violation error locally without additional request, and the second one uses a global error filter, catching such errors in the entire application. I personally use the latter.
Local no-db request solution
No need to make additional database request. You can catch the error violating the unique constraint and throw any HttpException you want to the client. In users.service.ts:
public create(newUser: Partial<UserEntity>): Promise<UserEntity> {
return this.usersRepository.save(newUser).catch((e) => {
if (/(email)[\s\S]+(already exists)/.test(e.detail)) {
throw new BadRequestException(
'Account with this email already exists.',
);
}
return e;
});
}
Which will return:
Global error filter solution
Or even create a global QueryErrorFilter:
#Catch(QueryFailedError)
export class QueryErrorFilter extends BaseExceptionFilter {
public catch(exception: any, host: ArgumentsHost): any {
const detail = exception.detail;
if (typeof detail === 'string' && detail.includes('already exists')) {
const messageStart = exception.table.split('_').join(' ') + ' with';
throw new BadRequestException(
exception.detail.replace('Key', messageStart),
);
}
return super.catch(exception, host);
}
}
Then in main.ts:
async function bootstrap() {
const app = await NestFactory.create(/**/);
/* ... */
const { httpAdapter } = app.get(HttpAdapterHost);
app.useGlobalFilters(new QueryErrorFilter(httpAdapter));
/* ... */
await app.listen(3000);
}
bootstrap();
This will give generic $table entity with ($field)=($value) already exists. error message. Example:

Answer 2

I have modified my code. I am checking the uniqueness of username/email in the user service (instead of a custom validator) and return an HttpExcetion in case the user is already inserted in the DB.

Answer 3

The easiest solution!
#Entity()
export class MyEntity extends BaseEntity{
#Column({unique:true}) name:string;
}
export abstract class BaseDataService<T> {
constructor(protected readonly repo: Repository<T>) {}
private async isUnique(t: any) {
const uniqueColumns = this.repo.metadata.uniques.map(
(e) => e.givenColumnNames[0]
);
for (const u of uniqueColumns) {
const count = await this.repo.count({ where: { [u]: ILike(t[u]) } });
if (count > 0) {
throw new UnprocessableEntityException(`${u} must be unique!`);
}
}
}
async save(body: DeepPartial<T>) {
await this.isUnique(body);
try {
return await this.repo.save(body);
} catch (err) {
throw new UnprocessableEntityException(err.message);
}
}
async update(id: number, updated: QueryDeepPartialEntity<T>) {
await this.isUnique(updated)
try {
return await this.repo.update(id, updated);
} catch (err) {
throw new UnprocessableEntityException(err.message);
}
}
}

Answer 4

An approach that works for modern version of NestJS which is based in Daniel Kucal's answer and actually returns the error to the frontend when calling the JSON API is the following:
import {
Catch,
ArgumentsHost,
BadRequestException,
HttpException,
} from '#nestjs/common';
import { BaseExceptionFilter } from '#nestjs/core';
import { QueryFailedError } from 'typeorm';
type ExceptionType = { detail: string; table: string };
#Catch(QueryFailedError)
export class QueryErrorFilter extends BaseExceptionFilter<
HttpException | ExceptionType
> {
public catch(exception: ExceptionType, host: ArgumentsHost): void {
const { detail = null } = exception || {};
if (
!detail ||
typeof detail !== 'string' ||
// deepcode ignore AttrAccessOnNull: <False positive>
!detail.includes('already exists')
) {
return super.catch(exception, host);
} // else
/**
* this regex transform the message `(phone)=(123)` to a more intuitive `with phone: "123"` one,
* the regex is long to prevent mistakes if the value itself is ()=(), for example, (phone)=(()=())
*/
const extractMessageRegex =
/\((.*?)(?:(?:\)=\()(?!.*(\))(?!.*\))=\()(.*?)\)(?!.*\)))(?!.*(?:\)=\()(?!.*\)=\()((.*?)\))(?!.*\)))/;
const messageStart = `${exception.table.split('_').join(' ')} with`;
/** prevent Regex DoS, doesn't treat messages longer than 200 characters */
const exceptionDetail =
exception.detail.length <= 200
? exception.detail.replace(extractMessageRegex, 'with $1: "$3"')
: exception.detail;
super.catch(
new BadRequestException(exceptionDetail.replace('Key', messageStart)),
host,
);
}
}
Also, not forgetting main.ts:
async function bootstrap() {
const app = await NestFactory.create(/**/);
/* ... */
const { httpAdapter } = app.get(HttpAdapterHost);
app.useGlobalFilters(new QueryErrorFilter(httpAdapter));
/* ... */
await app.listen(3000);
}
bootstrap();