Make FieldData respect to optional field.

[kidylee]

Current implementation of decorators, include: @IsFieldData, doesn't accept a FormData which has a optional file upload.

Please think of adding below parameters to make optional FieldData possible in DTO:

@IsFieldData({required: false })
file? FieldData

I could contribute it in a pr.

[h3llmy]

Since this validation is based on class-validator, you can utilize the @IsOptional() decorator provided by class-validator:

import { IsOptional } from 'class-validator';

@IsOptional()
@IsFileData()
files?: FileData;

[kidylee]

@IsOptional() doesn't escape @IsFileData() execute, hence it throws exception :

{
  "message": [
    "The value modelAvatarP must be an instance of FileData"
  ],
  "error": "Bad Request",
  "statusCode": 400
}

I'm not sure that I fully understood how class-validator works. Should @IsOptional() skips other decorators or individual decorator should detects @IsOptional() then skip the validation process?

[h3llmy]

base on class-validator documentation, the @IsOptional() decorator will Checks if given value is empty (=== null, === undefined) and if so, ignores all the validators on the property. so when the validation value is null or undefined it will skip all the validation rule on this property