ValidateNested throw 500, when it receives string or number instead of object

I have problem with ValidationNested and I hope that someone will know how handle with it.

Have you tried to send a request with a string or number in the place where the object should be (which is validated by a @ValidateNested annotation)? It will throw error with status code 500.

Example:

export class ClassA {
    @ValidateNested()
    @Type(() => ClassB) //annotation from class-transformer
    public company: ClassB;

    @IsOptional()
    @IsInt()
    public id?: number;
}

export class ClassB {
    @IsInt()
    public id: number;

    @IsString()
    @Length(1, 255) //class-validator will try count length of this string, no matter what :(
    public name: string;
}

POST request with body:

{
    company: 5,
    id: 3
}

response:

{
    "type": "http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html",
    "title": "Internal Server Error",
    "status": 500,
    "detail": "TypeError: Cannot read property 'length' of undefined\n ... } //class-validator has tried count ClassB.name length

I’m using class-validator 0.8.5, class-transformer 0.1.9 and routing-controllers 0.7.6

[chrisjpalmer]

Hi there.

Having a similar issue. It appears the validator is not picking up when the type is completely wrong, like where a string is in the place of an object. It will however correctly validate an object with incorrect fields. I have the following setup:

export class PostInput {
  @ValidateNested()
  @Type(() => PostInputMessage)
  @IsArray()
  entries: PostInputMessage[];
}

export class PostInputMessage {
  @IsString()
  message: string;
}

if my message input contains this:

{
       "entries":["Hello", "How are you"]
}

No validation error is thrown. However if my input looks like this:

{
      "entries":[{"pinapples":"Hello"}, {"pinapples":"How are you"}]
}

A validation error is correctly thrown. Versions: class-transformer 0.1.9, class-validator 0.8.1

[kiwikern]

@chrisjpalmer

Having a similar issue. It appears the validator is not picking up when the type is completely wrong, like where a string is in the place of an object. It will however correctly validate an object with incorrect fields.

I came across the same problem on Stackoverflow and proposed a custom validator as a workaround.