Support uploading files from multipart forms in Rails

[kimroen]

Hi! Recently, our form to upload verification documents to Stripe stopped working.

We do something that can be boiled down to this:

In the template:

<%= form_for :identity_verification do |f| %>
  <%= f.label :image, "Your identification" %>
  <%= f.file_field :image %>
<% end %>

In the controller

def create
  image = params[:identity_verification][:image]
  Stripe::FileUpload.create({
    purpose: 'identity_document',
    file: image
  })
end

After some digging, we realized that this started failing because Rails represents the uploaded file as an instance of ActionDispatch::Http::UploadedFile, and that Stripe now doesn't handle getting one of these passed in any more after switching from rest-client to Faraday.

Luckily in 1.8.1 the stripe gem introduced support for passing in a Tempfile, and you can get one of those out of the ActionDispatch::Http::UploadedFile instance by calling tempfile on it, so this fixed it for us:

 def create
   image = params[:identity_verification][:image]
   Stripe::FileUpload.create({
     purpose: 'identity_document',
-    file: image
+    file: image.tempfile
   })
 end

I understand the intention here is to not break the old behavior, so I just wanted to both let you know about this and document the fix so other people don't have to go spelunking like we did 👍

[kimroen]

In the interest of sharing, I thought it could be worth mentioning that rest-client determines if something is a file by checking that it responds to both path and read:

https://github.com/rest-client/rest-client/blob/f450a0f086f1cd1049abbef2a2c66166a1a9ba71/lib/restclient/payload.rb#L55

If you wanted to maintain the same API you could do the same thing. File, Tempfile and ActionDispatch::Http::UploadedFile all respond to both of these methods, so that would cover the things we know about so far, and might be better than checking is_a? with everything that could behave like a file.

[ob-stripe]

Hi @kimroen, thanks for the report! We recently reintroduced support for uploading Tempfiles in stripe-ruby v3.8.1, so you should be able to do:

  Stripe::FileUpload.create({
    purpose: 'identity_document',
    file: image.tempfile
  })

using the latest stripe-ruby.

That said, your proposal of mimicking rest-client's behavior makes a lot of sense! I'll run some tests and push a patch unless I run into any surprises.

[brandur-stripe]

We've released @ob-stripe's patch in 3.9.1.

[kimroen]

Perfect, thank you both ❤️