Rails + ActiveStorage on S3: Set filename on download? - ruby-on-rails

Question

Is there a way to change/set the filename on download?
Example: Jon Smith uploaded his headshot, and the filename is 4321431-small.jpg. On download, I'd like to rename the file to jon_smith__headshot.jpg.
View:
<%= url_for user.headshot_file %>
This url_for downloads the file from Amazon S3, but with the original filename.
What are my options here?

Answer 1

The built-in controller serves blobs with their stored filenames. You can implement a custom controller that serves them with a different filename:
class HeadshotsController < ApplicationController
before_action :set_user
def show
redirect_to #user.headshot.service_url(filename: filename)
end
private
def set_user
#user = User.find(params[:user_id])
end
def filename
ActiveStorage::Filename.new("#{user.name.parameterize(separator: "_")}__headshot#{user.headshot.filename.extension_with_delimiter}")
end
end
Starting with 5.2.0 RC2, you won’t need to pass an ActiveStorage::Filename; you can pass a String filename instead.

Answer 2

I know this was already answered, but I would like to add a second way of doing this. You could update your file name when the user object is saved. Using OP's example of the user model and the headshot_file field, this is how you could solve this:
# app/models/user.rb
after_save :set_filename
def set_filename
file.blob.update(filename: "ANYTHING_YOU_WANT.#{file.filename.extension}") if file.attached?
end

Answer 3

The approach of #GuilPejon will work. The problem with directly calling the service_url is:
It is short-lived (not recommended by rails team)
It will not work if the service is disk in development mode.
The reason it does not work for disk service is that disk service requires ActiveStorage::Current.host to be present for generating the URL. And ActiveStorage::Current.host gets set in app/controllers/active_storage/base_controller.rb, so it will be missing when service_url gets called.
ActiveStorage as of now gives one more way of accessing the URL of the attachments:
Using rails_blob_(url|path) (recommended way)
But if you use this, you can only provide content-disposition and not the filename.
If you see the config/routes.rb in the `ActiveStorage repo you will find the below code.
get "/rails/active_storage/blobs/:signed_id/*filename" => "active_storage/blobs#show", as: :rails_service_blob
direct :rails_blob do |blob, options|
route_for(:rails_service_blob, blob.signed_id, blob.filename, options)
end
and when you look into blobs_controller you will find the below code:
def show
expires_in ActiveStorage::Blob.service.url_expires_in
redirect_to #blob.service_url(disposition: params[:disposition])
end
So it is clear that in rails_blob_(url|path) you can only pass disposition and nothing more.

Answer 4

I haven't played with ActiveStorage yet, so this is kind of a shot in the dark.
Looking at the ActiveStorage source for the S3 service, it looks like you can specify the filename and disposition for the upload. From the guides it seems that you can use rails_blob_path to access the raw URL of the upload and pass these parameters. Therefor you might try:
rails_blob_url(user.headshot_file, filename: "jon_smith__headshot.jpg")