How to preserve the original file name as original_filename of a submitted file?

Question

My users are submitting files that should be passed on to a third party.

The files are submitted as params[:files]:

= form_with :url => files_path, :method => :create, :multipart => true do
    = file_field_tag "files[]", :multiple => true

From my controller, they look like this:

[#<ActionDispatch::Http::UploadedFile:0x0000000103c1c678 @tempfile=#<Tempfile:/var/folders/k7/n71v0f_n2nb3pzyj38s5y9x80000gn/T/RackMultipart20220902-12314-in3y4h.txt>, @original_filename="test.txt", @content_type="text/plain", @headers="Content-Disposition: form-data; name=\"files[]\"; filename=\"test.txt\"\r\nContent-Type: text/plain\r\n">]

I go through the files like this:

params[:files].each do|file|
  HTTParty.post(
    "https://example.com/files",
    headers: {
      "Accept"        => "application/json",
      "Content-Type"  => "multipart/form-data"
    },
    body: {
      "file"          => File.open(file.tempfile)
    }
  )
end

Even though the files have a file.original_filename property, the one submitted in my POST request is the randomly temporary one. In this example RackMultipart20220902-12314-in3y4h.txt. Here is a trimmed log from my request:

<- "POST /files HTTP/1.1\r\nAccept: application/json\r\nContent-Type: multipart/form-data; boundary=------------------------dnh46jyEwRV85_DO\r\nAccept-Encoding: gzip;q=1.0,deflate;q=0.6,identity;q=0.3\r\nUser-Agent: Ruby\r\nConnection: close\r\nHost: example.com\r\nContent-Length: 433\r\n\r\n"
<- "--------------------------dnh46jyEwRV85_DO\r\nContent-Disposition: form-data; name=\"file\"; filename=\"RackMultipart20220902-12314-in3y4h.txt\"\r\nContent-Type: text/plain\r\n\r\nhello\r\n--------------------------dnh46jyEwRV85_DO\\r\n"
-> "HTTP/1.1 200 OK\r\n"

This means that the original file names are lost between me and the third party. How can I change that?

Answer 1

original_filename is the correct way to go. However, you are seeing a temporary file because you triggered the HTTP request via HTTParty API client, and not the upload form in the UI.

I see the upload has User-Agent: Ruby. In that case, you get the filename that HTTParty generated when loaded the file in memory as tempfile.

Try to upload it from the form UI, and you will get the original filename from your disk.