Shrine setup

document.rb

  include FileUploader::Attachment.new(:file)

documents-edit.html.erb

...
<%= f.check_box :parse, label: (document.file.present? && document.file[:original].exists? ? document.file[:original].original_filename : 'Attached file') %>
...

file_uploader.rb

class FileUploader < Shrine
  plugin :processing
  plugin :versions
  plugin :remove_attachment
  
  process(:convert) do |io, context|
    doc = begin
      io[:original].download
    rescue
      io.download
    end

    output_html = Tempfile.new(%w[pandoc .md], binmode: true)
    system *%W[pandoc #{doc.path} -t html5 -o #{output_html.path}]
    output_html.open
    context[:record].body_html = output_html.read
    output_html.rewind

    { original: doc, html: output_html }
  end
  
  process(:store) do |io, context|
    {original: io}
  end

end

raw_uploader.rb

class RawUploader < Shrine
  plugin :remove_attachment
  
end

user.rb

  include RawUploader::Attachment.new(:cv)

users_controller.rb

  def download
    temp = @user.cv.download
    send_file temp, disposition: 'attachment', filename: @user.cv.original_filename,
              type: @user.cv.mime_type, stream: true, buffer_size: 4096
  end

The users (with the raw_uploader) work perfectly, but the documents (with the file_uploader) give me the shrine tempfile name instead.