flashcards-api/src/settings/pipes-setup.ts

import { BadRequestException, INestApplication, ValidationPipe } from '@nestjs/common'
import { ValidationError } from 'class-validator'

export const validationErrorsMapper = {
  mapValidationErrorArrayToValidationPipeErrorTypeArray(
    errors: ValidationError[]
  ): ValidationPipeErrorType[] {
    return errors.flatMap(error => {
      const constraints = error.constraints ?? []
      return Object.entries(constraints).map(([_, value]) => ({
        field: error.property,
        message: value,
      }))
    })
  },
}

export function pipesSetup(app: INestApplication) {
  app.useGlobalPipes(
    new ValidationPipe({
      whitelist: true,
      transform: true,

      stopAtFirstError: true,
      exceptionFactory: (errors: ValidationError[]) => {
        const err =
          validationErrorsMapper.mapValidationErrorArrayToValidationPipeErrorTypeArray(errors)
        throw new BadRequestException(err)
      },
    })
  )
}

export type ValidationPipeErrorType = {
  field: string
  message: string
}