The backend expects to receive a null value when using data part with multipart/form-data

[Denis Marinx]

Question

Description

I've been used to Fuel for a long time and I'm probably asking here a stupid question but I'm not used to communicate with the backend with multipart/form-data.
I cannot send a "null" value as DataPart of UploadRequest.

UseCase - send to the backend a file datapart with a specific key with value set to null

    // key is here:  user[avatar]
    private fun UploadRequest.addPhotoAction(key: String, photoAction: PhotoAction){
        when(photoAction){
            is PhotoAction.Defined.Set -> { // works fine
                val file = File(UriCompose.getPathFromInputStreamUri(context = applicationContext, photoAction.uriString.toUri()))
                if(file.exists()){
                    add(FileDataPart(file = file, name = key, contentType = ContentTypeMultiPartSupported.MultiPartFormData.contentType))
                }
            }
            is PhotoAction.Delete -> { // !!! cannot set the file parameter to null !!!
                // cannot set a file parameter value to null
                add(FileDataPart(file = null, name = key, contentType = ContentTypeMultiPartSupported.MultiPartFormData.contentType))
                // cannot either set a content parameter value to null
                //add(InlineDataPart(content = null, name = key, contentType = ContentTypeMultiPartSupported.Text.contentType))
            }
        }
    }

Expected behavior

The backend expects to receive a null value and I cannot set a null value to a content/file parameter of DataPart

[Kittinun Vantasin]

Just wondering when we send null, what exactly the backend would receive? It is a string "null" or something?

[Denis Marinx]

I had my answer 5 days ago and I forgot to close this issue (I was busy this week). It was an issue from the backend developer. There is no way in multipart to send a value to "null". Just ends up to communicate in another way. Sorry to disturb you. Great library by the way. I close the issue.