Optional Upload with malformed file multipart part

[DrorBuhnik]

When we have this endpoint:

@POST
public Result create(Optional<Upload> file, String other) {...}

And the client upload a multipart with 'file' part where the 'filename' doesn't exists we get weird result, file.isPresent() return true but he is a 'Object' type instead of 'Upload'
Currently we manually check it:

if (file.isPresent()) {
    if (!(file.get() instanceof Upload)) {
        throw new Exceptions.BadRequest("Upload 'file' is missing (did you put 'filename'?)");
    }
}

[jknack]

Will have to look, didn't know the filename attribute was optional

[DrorBuhnik]

I'm not sure it is optional
I'm completely fine if such malformed part will result in Bad Request 400