Обробка Validation Errors

{
  "email": "invalid",
  "name": 42,
  "age": 15
}

{
  "statusCode": 400,
  "message": [
    "email must be an email",
    "name must be a string",
    "age must not be less than 18"
  ],
  "error": "Bad Request"
}

{
  property: 'email',
  value: 'invalid',
  constraints: {
    isEmail: 'email must be an email'
  },
  children: []
}

import { ValidationError } from 'class-validator';

export interface ValidationErrorDetail {
  field: string;
  code: string;
  message: string;
}

export function flattenValidationErrors(
  errors: ValidationError[],
  parentPath = '',
): ValidationErrorDetail[] {
  const details: ValidationErrorDetail[] = [];

  for (const error of errors) {
    const field = parentPath
      ? `${parentPath}.${error.property}`
      : error.property;

    if (error.constraints) {
      for (const [code, message] of Object.entries(error.constraints)) {
        details.push({
          field,
          code,
          message,
        });
      }
    }

    if (error.children?.length) {
      details.push(...flattenValidationErrors(error.children, field));
    }
  }

  return details;
}

{
  "field": "profile.address.city",
  "code": "isString",
  "message": "city must be a string"
}

import {
  BadRequestException,
  HttpStatus,
  ValidationPipe,
} from '@nestjs/common';
import { flattenValidationErrors } from './flatten-validation-errors';

export const validationPipe = new ValidationPipe({
  transform: true,
  whitelist: true,
  forbidNonWhitelisted: true,

  exceptionFactory: (errors) => {
    const details = flattenValidationErrors(errors);

    return new BadRequestException({
      statusCode: HttpStatus.BAD_REQUEST,
      code: 'VALIDATION_ERROR',
      message: 'Дані запиту не пройшли валідацію',
      details,
    });
  },
});

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { validationPipe } from './validation.pipe';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  app.useGlobalPipes(validationPipe);

  await app.listen(3000);
}

bootstrap();

{
  "statusCode": 400,
  "code": "VALIDATION_ERROR",
  "message": "Дані запиту не пройшли валідацію",
  "details": [
    {
      "field": "email",
      "code": "isEmail",
      "message": "email must be an email"
    },
    {
      "field": "name",
      "code": "isString",
      "message": "name must be a string"
    },
    {
      "field": "age",
      "code": "min",
      "message": "age must not be less than 18"
    }
  ]
}

for (const error of response.details) {
  form.setError(error.field, {
    message: error.message,
  });
}

import { IsEmail, IsInt, IsString, Min } from 'class-validator';

export class CreateUserDto {
  @IsEmail()
  email: string;

  @IsString()
  name: string;

  @IsInt()
  @Min(18)
  age: number;
}

import { Body, Controller, Post } from '@nestjs/common';
import { CreateUserDto } from './create-user.dto';

@Controller('users')
export class UsersController {
  @Post()
  create(@Body() dto: CreateUserDto) {
    return {
      id: 1,
      email: dto.email,
      name: dto.name,
      age: dto.age,
    };
  }
}

import { ValidationError } from 'class-validator';

export function flattenValidationErrors(
  errors: ValidationError[],
  parentPath = '',
) {
  const details: Array<{
    field: string;
    code: string;
    message: string;
  }> = [];

  for (const error of errors) {
    const field = parentPath
      ? `${parentPath}.${error.property}`
      : error.property;

    for (const [code, message] of Object.entries(
      error.constraints ?? {},
    )) {
      details.push({
        field,
        code,
        message,
      });
    }

    if (error.children?.length) {
      details.push(...flattenValidationErrors(error.children, field));
    }
  }

  return details;
}

import {
  BadRequestException,
  HttpStatus,
  ValidationPipe,
} from '@nestjs/common';
import { flattenValidationErrors } from './flatten-validation-errors';

export const appValidationPipe = new ValidationPipe({
  transform: true,
  whitelist: true,
  forbidNonWhitelisted: true,

  exceptionFactory: (errors) => {
    const details = flattenValidationErrors(errors);

    return new BadRequestException({
      statusCode: HttpStatus.BAD_REQUEST,
      code: 'VALIDATION_ERROR',
      message: 'Дані запиту не пройшли валідацію',
      details,
    });
  },
});

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { appValidationPipe } from './app-validation.pipe';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  app.useGlobalPipes(appValidationPipe);

  await app.listen(3000);
}

bootstrap();

new ValidationPipe({
  whitelist: true,
});

new ValidationPipe({
  whitelist: true,
  forbidNonWhitelisted: true,
});

{
  "email": "user@example.com",
  "name": "Anna",
  "age": 25,
  "isAdmin": true
}

{
  "field": "isAdmin",
  "code": "whitelistValidation",
  "message": "property isAdmin should not exist"
}

import { IsEmail, IsString, MinLength } from 'class-validator';

export class CreateUserDto {
  @IsEmail({}, { message: 'Вкажіть коректну електронну адресу' })
  email: string;

  @IsString({ message: 'Ім’я має бути текстом' })
  @MinLength(2, { message: 'Ім’я має містити щонайменше 2 символи' })
  name: string;
}

{
  "field": "name",
  "code": "minLength",
  "message": "Ім’я має містити щонайменше 2 символи"
}

exceptionFactory: (errors) => {
  const fields = flattenValidationErrors(errors).map(({ field, code }) => ({
    field,
    code,
  }));

  return new BadRequestException({
    statusCode: 400,
    code: 'VALIDATION_ERROR',
    message: 'Некоректні дані запиту',
    details: fields,
  });
},

{
  "statusCode": 400,
  "code": "VALIDATION_ERROR",
  "message": "Некоректні дані запиту",
  "details": [
    {
      "field": "email",
      "code": "isEmail"
    }
  ]
}

import { IsInt, IsOptional, IsString, Min } from 'class-validator';

export class ListUsersQueryDto {
  @IsOptional()
  @IsString()
  search?: string;

  @IsOptional()
  @IsInt()
  @Min(1)
  page?: number;
}

import { Controller, Get, Query } from '@nestjs/common';
import { ListUsersQueryDto } from './list-users-query.dto';

@Controller('users')
export class UsersController {
  @Get()
  findAll(@Query() query: ListUsersQueryDto) {
    return {
      query,
    };
  }
}

{
  "statusCode": 404,
  "code": "USER_NOT_FOUND",
  "message": "Користувача не знайдено"
}

{
  "statusCode": 400,
  "code": "VALIDATION_ERROR",
  "message": "Дані запиту не пройшли валідацію",
  "details": []
}

if (error.code === 'VALIDATION_ERROR') {
  // Показати помилки біля полів форми
}

if (error.code === 'USER_NOT_FOUND') {
  // Показати повідомлення про відсутнього користувача
}

exceptionFactory: (errors) => {
  return new BadRequestException(errors);
};

for (const error of errors) {
  // Обробляються тільки constraints поточного рівня
}

if (message === 'email must be an email') {
  // ...
}