Support for optional file validation

[mondyfy]

Current Behavior: When using the nestjs-form-data package, it seems that there is no built-in support for handling optional file validation. The library provides excellent support for handling file uploads, but it lacks a feature to easily specify that a file upload is optional and should not trigger validation errors if absent.

Validations used:

Expected Behavior: I would expect the nestjs-form-data library to have a mechanism to define certain file fields as optional, meaning that if a file is not provided during the upload, it should not trigger validation errors.

Steps to Reproduce:

1. Attempt to create an endpoint using nestjs-form-data where a file upload is optional.
2. Upload a request without the optional file field.
3. Observe that validation errors are still triggered even though the file is optional.

Environment:

• nestjs-form-data version: 1.9.0
• NestJS version: 9.0.0
• Node.js version: 18.12.0

Additional Context: I believe that adding support for optional file validation would enhance the usability and flexibility of the nestjs-form-data, especially in scenarios where certain files are not required for every upload.

[dmitriy-nz]

@mondyfy
Hi! Thanks for your feedback! For mark field as optional use @IsOptional() decorator then class-validator will know that the field is optional. Here's an example

[dmitriy-nz]

Please close your issue if it is solved

[mondyfy]

Sorry I missed that part, the issue was with the null value passed in the key:

curl --request POST \
  --url http://localhost:3000/api/v1/candidate-story \
  --header 'Content-Type: multipart/form-data' \
  --form file=

As it has been resolved, closing as completed. Thank you @dmitriy-nz