Nest: ValidationPipe cannot validate Arrays

Created on 21 Jun 2018 · 6Comments · Source: nestjs/nest

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[ ] Regression 
[ ] Bug report
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

I need to validate the body of a request, that is an array of createCatDto, but inside the ValidationPipe, the metatype comes out as Array but the createCatDto gets lost and cannot validate the type.

Expected behavior

Passing the metatype externally so I can validate every entry of the array with the proper class.

Minimal reproduction of the problem with instructions

@Patch()
editCats(@Body() editCatDto: EditCatDto[]) {
  return this.cat.updateBatch(editCatDto);
}

Environment


Nest version: 5.0.1


For Tooling issues:
- Node version: 8.11.1  
- Platform:  Mac

Source

kikar

Most helpful comment

Following the example of AuthGuard, I implemented an ArrayValidationPipe that could be useful to anyone trying to validate plain arrays in HTTP body. At the moment I am not sure how to make it work as a singleton, but I use a memoize function for that performance.

Code:

import { ArgumentMetadata, mixin, PipeTransform, Type, ValidationPipe } from '@nestjs/common';
import { memoize } from 'lodash';

export const ArrayValidationPipe: <T>(itemType: Type<T>) => Type<PipeTransform> = memoize(createArrayValidationPipe);

function createArrayValidationPipe<T>(itemType: Type<T>): Type<PipeTransform> {
  class MixinArrayValidationPipe extends ValidationPipe implements PipeTransform {

    transform(values: T[], metadata: ArgumentMetadata): Promise<any[]> {
      if (!Array.isArray(values)) {
        return values;
      }

      return Promise.all(values.map(value => super.transform(value, { ...metadata, metatype: itemType })));
    }
  }

  return mixin(MixinArrayValidationPipe);
}

Usage:
@Body(ArrayValidationPipe(User)) users: User[]

Nosfistis on 5 Jun 2019

❤2 👍1

All 6 comments

That is impossible through reflection: https://github.com/nestjs/nest/issues/335#issuecomment-365617027. I'd suggest creating your own validation pipe that extends existing one.

kamilmysliwiec on 21 Jun 2018

It is ok that it does not work out of the box, but would it be possible to type hint an array of mydto somehow?

chartinger on 13 Nov 2018

How can I make ValidationPipe to throw validation error when incoming body is array, but I'm waiting SomeKindDto?
Now it breaks my service if someone sends me an array in API.

evilive3000 on 15 Apr 2019

Code:

import { ArgumentMetadata, mixin, PipeTransform, Type, ValidationPipe } from '@nestjs/common';
import { memoize } from 'lodash';

export const ArrayValidationPipe: <T>(itemType: Type<T>) => Type<PipeTransform> = memoize(createArrayValidationPipe);

function createArrayValidationPipe<T>(itemType: Type<T>): Type<PipeTransform> {
  class MixinArrayValidationPipe extends ValidationPipe implements PipeTransform {

    transform(values: T[], metadata: ArgumentMetadata): Promise<any[]> {
      if (!Array.isArray(values)) {
        return values;
      }

      return Promise.all(values.map(value => super.transform(value, { ...metadata, metatype: itemType })));
    }
  }

  return mixin(MixinArrayValidationPipe);
}

Usage:
@Body(ArrayValidationPipe(User)) users: User[]

Nosfistis on 5 Jun 2019

❤2 👍1

Following the example of AuthGuard, I implemented an ArrayValidationPipe that could be useful to anyone trying to validate plain arrays in HTTP body. At the moment I am not sure how to make it work as a singleton, but I use a memoize function for that performance.

Code:
import { ArgumentMetadata, mixin, PipeTransform, Type, ValidationPipe } from '@nestjs/common';
import { memoize } from 'lodash';

export const ArrayValidationPipe: <T>(itemType: Type<T>) => Type<PipeTransform> = memoize(createArrayValidationPipe);

function createArrayValidationPipe<T>(itemType: Type<T>): Type<PipeTransform> {
  class MixinArrayValidationPipe extends ValidationPipe implements PipeTransform {

    transform(values: T[], metadata: ArgumentMetadata): Promise<any[]> {
      if (!Array.isArray(values)) {
        return values;
      }

      return Promise.all(values.map(value => super.transform(value, { ...metadata, metatype: itemType })));
    }
  }

  return mixin(MixinArrayValidationPipe);
}
Usage:
@Body(ArrayValidationPipe(User)) users: User[]

Best solution I have ever seen.